Dinosaurs and Prehistoric Life

DINOSAURSENCYCLOPEDIA OF

& PREHISTORIC LIFE

A Dorling Kindersley Book

In association with theAMERICAN MUSEUM OF NATURAL HISTORY

DINOSAURSENCYCLOPEDIA OF

& PREHISTORIC LIFE

Senior Art EditorMartin Wilson

Art EditorsStephen Bere, Tim Brown, Diane Clouting, Sarah Crouch, Darren Holt, Robin Hunter,

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First American Edition published in 2001This paperback edition first published in 2008 by

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ISBN: 978-0-7566-3836-8

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LONDON, NEW YORK, MUNICH, PARIS, MELBOURNE, and DELHI

4

Discover more at

How to use this book 8Finding out about the past 10

Fossils 12Evolving life 14

How evolution happens 16Classifying life 18

5

AMPHIBIANS ANDREPTILES 54–99

Early tetrapods and amphibians cladogram 56Early tetrapods 58Temnospondyls 60

Life in a swamp forest 62Lepospondyls and lissamphibians 64

Reptiliomorphs 66Introducing amniotes 68

Reptiles cladogram 70Parareptiles 72

Turtles 74Diversifying diapsids 76

Mosasaurs 78Placodonts and nothosaurs 80Short-necked plesiosaurs 82Long-necked plesiosaurs 84

Ichthyosaurs 86Early ruling reptile groups 88

Early crocodile-group reptiles 90Crocodylomorphs 92Early pterosaurs 94

Advanced pterosaurs 98

CONTENTS

Invertebrates cladogram 22Trilobites 24

Sea scorpions 26Evolving insects 28

Ammonites and belemnites 30Toward the first fish 32

Vertebrates cladogram 34Fish cladogram 36

Jawless fish 38Armored fish 40

Sharks and rays 44Spiny sharks 46

Early ray-finned fish 48Advanced ray-finned fish 50

Lobe-finned fish 52

FISH ANDINVERTEBRATES 20–53

6

Dinosaurs defined 102Saurischians cladogram 104

Early theropods 106Horned lizards 108Abel’s lizards 110

Stiff tails 112Strange spinosaurs 114

Giant killers 116Predator trap 118

Hollow-tail lizards 120Ostrich dinosaurs 122

Tyrannosaurids 124Scythe lizards 126Egg thieves 130Tail feather 132

Terrible claws 134Road runners 136

Birds cladogram 138Archaeopteryx 140

Early birds 142New birds 144

Introducing sauropodomorphs 148Prosauropods 150

Early sauropods 152Double beams 154

Chambered lizards 156Arm lizards 158

Gigantic lizards 160Brachiosaurids 162

Ornithischians cladogram 164Small bipedal plant eaters 166

Early shield bearers 168Plated dinosaurs 170

Spiky backs 172Node lizards 174Fused lizards 176

Camptosaurs and dryosaurs 178Iguanodon 180

Duck-billed dinosaurs 182Thick-headed lizards 184

Parrot lizards 186Early horned dinosaurs 188

Advanced horned dinosaurs 190

DINOSAURSAND BIRDS 100–191

7

MAMMALS AND THEIRANCESTORS 192–275

Synapsids cladogram 194Early synapsids 196Terrible heads 198Two dog teeth 200

Dog teeth 202The first mammals 204

Australian pouched mammals 206American pouched mammals 208

Strange-jointed mammals 210Placental pioneers 212Early carnivorans 214

Cats and other feliforms 216Saber-toothed cats 218

Dogs and other caniforms 220Insectivores and bats 224

Primitive primates 226Monkeys 228

Australopithecines 230Early homo species 232

Neanderthals 234Homo sapiens 236

Prehistoric rabbits and rodents 238Island giants and dwarfs 240

Terrible horns 242Primitive hoofed mammals 244

South American hoofed mammals 246Uranotheres 250

Horses 252Brontotheres and chalicotheres 254

Rhinoceroses 256

Proboscideans 258Platybelodon 260Mammoths 262

Pigs, hippos, and peccaries 264Camels 266

Deer and kin 268Cattle, sheep, and goats 270

Hoofed predators 272Early whales 274

Fossil timeline 278Finding fossils 312

Techniques of excavation 314Famous fossil sites 316Fossils in the lab 318Studying fossils 320

Paleobotany 322Paleoecology 324

Comparative dating 326Chronometric dating 328Reconstructing fossils 330

Restoring fossil animals 332Fossil hunter 334Biographies 344

The past on display 358Glossary and additional

pronunciation guide 360Index 366

Acknowledgments 375

REFERENCESECTION 276–376

SAIL-BACKED KILLERDimetrodon was one of the first big land animals to becapable of attacking and killing creatures its own size.This pelycosaur had a large, long, narrow head, withpowerful jaws and dagger-like teeth. Dimetrodon couldgrow up to 3.5 m (11 ft 6 in) in length. It survived by attacking large, plant-eating pelycosaurs. Dimetrodonlived during the Early Permianin what is now North Americaand Europe. Its remains have been found in Texas and Oklahoma, in the USA,and in Europe.

196196

Devonian 410–355 Carboniferous 355–295 Permian Cambrian 540–500 Ordovician 500–435

EARLY SYNAPSIDSSYNAPSIDS (“WITH ARCH”) INCLUDE the mammal-like “reptiles” and theirdescendants, the mammals. They are named for the large hole low in the skull behind each eye. Muscles that worked the jaws passedthrough this hole, and gave synapsids a wide gape and powerful bite.Synapsids formed a separate group from true reptiles, who gave rise to lizards, dinosaurs, and their relatives. Like living reptiles, however,early kinds were scaly and cold-blooded. Synapsids appeared duringthe Carboniferous period. Early synapsids are known as pelycosaurs,and were quadrupeds with sprawling limbs. Most pelycosaurs lived in what is now North America and Europe. By early Permian times,pelycosaurs counted for seven out of ten backboned land animals.The early synapsids died out towards the end of the Permian period.

TYPES OF TEETHMost reptiles have teeth

of similar shapes. Dimetrodon’s teethhad different shapes, like a mammal’s.The name Dimetrodon means “two types of teeth”. The differently shaped teethhad various functions. The pointedupper canine teeth were designed forpiercing flesh. The sharp front teethserved for biting and gripping. The small back teeth aided in chewing up chunks of flesh.

Dimetrodon skull

MAMMALS AND THEIR ANCESTORS

Silurian 435–410

PALAEOZOIC 540–250 MYA

Sunshine could havewarmed Dimetrodon’sbody by heating theblood that flowedthrough its sail.

Canine teeth withserrated blades

Dimetrodon

26 2726 27

Devonian 416–359.2 Carboniferous 359.2–299 Triassic 251–199.6Permian 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Palaeogene 65.5–23Cambrian 542–488.3 Ordovician 488.3–443.7 Neogene 23–present

EURYPTERIDS(SEA SCORPIONS)were the largest-ever arthropods.They belong to thechelicerates (“bitingclaws”), a group thatincludes scorpions and spiders.Sea scorpions appeared inOrdovician times and persistedinto the Permian. Among thelargest was Pterygotus, which livedmore than 400 million years ago, andcould grow longer than a man. Beforepredatory fish evolved, sea scorpionswere among the most dominant huntersof shallow seas. Some species even crawledashore, where they breathed air by means ofspecial “lungs”, like those of certain land crabs.

MESOZOIC 251–65.5 MYA CENOZOIC 65.5 MYA–present

HUNTERS AND SCAVENGERSMany species of sea scorpion were muchsmaller and less well-armed than Pterygotus.Eurypterus was only 10 cm (4 in) long, andhad two short fangs. It would not have beenable to tackle the large prey that Pterygotuslived on. These creatures used their legs topull tiny animals toward their fangs, whichtore them up and fed them to the mouth.

Large eye

Pterygotus swam bybeating its broadpaddles up and down.

Huge fangs (chelicerae)similar to a lobster’s claws

FISH AND INVERTEBRATES SEA SCORPIONS

Silurian 443.7–416


BODY PLANLike all sea scorpions, Pterygotus had a two-part body. Its prosoma (front) bore the mouth, one pair of large eyes, one pair of small eyes, and six pairs of appendages. The long opisthosoma (rear) had 12plated tail segments called tergites. The first six tergites

contained pairs of gills, and included the creature’ssex organs. Pterygotus’s telson, or tail, formed a

wide, short paddle. In some sea scorpions,the telson took the shape of pincers

or a spike.

METHOD OF ATTACKPterygotus had big, keen eyes that could detectthe movement of small, armoured fish on themuddy sea floor some way ahead. The huntercould have crawled or swum slowly towards its victim, then produced an attacking burst of speed by lashing its telson up and down.Before the fish could escape, it would begripped between the pincers of a great clawwith spiky inner edges. This fang would crushthe struggling fish and feed it to Pterygotus’smouth, which lay beneath its prosoma and between its walking legs.

SEA SCORPIONS PTERYGOTUS

Walking leg

Small eye

Scientific name: PterygotusSize: Up to 2.3 m (7 ft 4 in) longDiet: FishHabitat: Shallow seasWhere found: Europe and North AmericaTime: Late SilurianRelated genera: Jaekelopterus, Slimonia


196196

Devonian 410–355 Carboniferous 355–295 Permian Cambrian 540–500 Ordovician 500–435




Dimetrodon skull


Silurian 435–410




Dimetrodon


196196

Devonian 416–359.2 Carboniferous 359.2–299 Permian Cambrian 542–488.3 Ordovician 488.3–443.7




Dimetrodon skull






Dimetrodon

The rostral bone grew at the tip of the upper jaw andformed a powerful beak.

In stegosaurs such asStegosaurus, the armourplates were arranged in tworows along the midline ofthe body.

All ornithischians descendedfrom long-legged, bipedalancestors, such asHeterodontosaurus.

The predentary bone is asingle U-shaped bone thatis covered in life by a horny beak.

165164

ORNITHISCHIANS CLADOGRAMTHE “BIRD-HIPPED” DINOSAURS called ornithischians include thearmoured stegosaurs, the horned ceratopsians, and the duck-billedhadrosaurs. All ornithischians share key features of the jaws and teeth that allowed them to crop and chew plants efficiently. Advancedornithischians, especially the hadrosaurs, became highly modified for chewing plants. They evolved hundreds of self-sharpening teethand special skull hinges that helped them grind their teeth together.All ornithischians probably evolved from a bipedal ancestor similar to Heterodontosaurus, one of the most primitive ornithischians.

DINOSAURS AND BIRDS

HETERODONTOSAURUS

THYREOPHORANS

ORNITHOPODS

PACHYCEPHALOSAURS

CERATOPSIANS

PREDENTARY BONEGrooves on the predentarybone’s hind margins allowedthe two dentary bones in thelower jaw to rotate slightly.This let ornithischians rotatetheir tooth rows and therebychew their food.

INSET TOOTH ROWThe Genasauria are united byhaving chewing teeth that areset in from the side of theface. Heterodontosaurus showedthis feature yet seems primitive in other ways. Perhaps allornithischians had an inset tooth row.

ROW OF SCUTESThyreophorans had armourplates in rows along theirbodies. Early thyreophoranswere fast, partially bipedaldinosaurs, but advancedforms had short feet andwere slow-moving animalsthat relied on body armourfor defence.

ASYMMETRICAL ENAMELCerapods had a thicker layerof enamel on the inside oftheir lower teeth. The teethwore unevenly with chewingand developed sharp ridgesthat allowed cerapods tobreak down tougher plantfood than other dinosaurs.

SHELF ON BACK OF SKULLA bony shelf that jutted outfrom the back of the skull is the key characteristic thatunites the marginocephalians.It only developed when theanimals became mature, and may have evolved for use in display.

ROSTRAL BONECeratopsians – the hornedmarginocephalians – are unitedby the presence of the rostralbone. This toothless structureformed an enlarged cutting areaon the beak. Early ceratopsianswere about 1 m (3 ft 3 in) long,but Late Cretaceous forms wereas big as the largest elephants.

Triceratops

ORNITHISCHIAN EVOLUTIONDespite descending from similar ancestors, the differentornithischian groups evolved distinct modes of life.Thyreophorans walked on all fours, while ornithopodsdiversified as small, bipedal (two-legged) runners. Large, partly quadrupedal ornithopods with widenedbeaks evolved late in the Jurassic. Marginocephalians date from the Mid Jurassic. Pachycephalosaurs andprimitive ceratopsians remained bipedal, while theadvanced Cretaceous ceratopsians walked on all fours.

ORNITHISCHIANS CLADOGRAM

Skull and jaws of Cretaceousornithischian Ouranosaurus Inset tooth rows

Skull and jaws of Jurassicornithopod Heterodontosaurus

Scute

Cretaceous ankylosaurEdmontonia

Thick enamellayer

Bone of lower jaw

Unerupted tooth

Section through hadrosaur jaw

Iguanodon and otheradvanced ornithopodswere large and may havewalked on all fours.

Stegoceras belonged to agroup of pachycephalosaursthat had thick, rounded skulldomes, which were probablyused in display and combat.

Skull and jaws of Cretaceousceratopsian Triceratops

ORNITHISCHIAPredentary bone

GENASAURIATooth row inset

from jaw margins

Row of scutes on body

CERAPODAAsymmetrical enamel

on cheek teeth

MARGINOCEPHALIAShelf on back of skull

Rostral bone

Bony shelf

Stegoceras skull

Inside of thelower jaw

88

HOW TO USE THIS BOOK

FEATURE PAGESRealistic restorations of a prehistoric animalset in its natural habitat are found in featurepages throughout the four main sections.Detailed text describes the main animal andother related creatures. These pages (above)describe sea scorpions, and feature the sea scorpion Pterygotus.

CLADOGRAM PAGESThe book contains ninecladogram diagrams withinthe main sections. Eachcladogram shows the chainof evolution for a particulargroup of animals. Color-coded branches make eachcladogram easy to follow.Significant features aredescribed in the text. Thesepages (right) represent the cladogram forornithischian dinosaurs.


A speciallycommissionedmodel provides alifelike restorationof a prehistoricanimal.

Specially commissionedartworks illustrate keyfeatures and sample species.

THE ENCYCLOPEDIA OF DINOSAURS and other prehistoriclife begins with an introductory section that providesan overview to understanding fossils, evolution, andprehistoric life. This is followed by the four mainsections of the book, which cover the major groups of prehistoric animals – Fish and Invertebrates,Amphibians and Reptiles, Dinosaurs and Birds, andMammals and their Ancestors. Each entry in thesefour sections covers a particular prehistoric animal or a group of such animals. An extensive referencesection at the back of the book contains a fossiltimeline, details of how paleontologists find and study fossils, and biographies of noted researchers.

Colored section bordershelp the reader locatesections easily.

Abbreviations used in this book

MYA millions of years agoc. about

Imperialft feetin inchesºF degrees Fahrenheitoz ounceslb poundscu in cubic inches

Metricm meterscm centimetersºC degrees Celsiusg gramskg kilogramskm kilometerscc cubic centimeters

ANIMAL PAGESThe main sections consist mostly of animalpages, which focus on groups of prehistoricanimals. The pages shown above describeearly synapsids. A typical animal – hereDimetrodon – is displayed prominently. The entry begins with an introduction that describes features of the animal group.It then gives details of the main animal’sanatomy and lifestyle, as well as facts on other animals in the group.

Photographs and colorfulartworksaccompany text.

SKIN SAILThe skin sail rising from Dimetrodon’s back was

a special feature whose likely purpose was tohelp control body temperature. Edaphosaurusalso had a tall skin sail on its back. Skin sailsmay have helped pelycosaurs keep cool inhot weather or be active in the morningwhile their prey was still cold and sluggish.The sail may also have aided recognitionamong members of a species.

197197

Triassic 250–203 295–250 Jurassic 203–135 Cretaceous 135–65 Tertiary 65–1.75 Quaternary 1.75–present

MESOZOIC 250–65 MYA CENOZOIC 65 MYA–present

EARTH LIZARDEdaphosaurus (“earth lizard”) was a large, early plant-eating pelycosaur. Its broad, short head was small for its hefty, 3-m (10-ft) long body. Its barrel-shaped body

had room for the large gut needed fordigesting bulky plant food, although

some scientists believe its peg-shapedteeth were best suited for crushing

shellfish. Edaphosaurus lived inNorth America and Europefrom the Late Carboniferous to the Early Permian. Its worstenemy was another pelycosaur –

the meat-eating Dimetrodon.

TWO TYPES OF TEETH

Scientific name: DimetrodonSize: Up to 3.5 m (11 ft 6 in) longDiet: MeatHabitat: Semi-desertWhere found: North America and EuropeTime: Early PermianRelated genera: Haptodus, Sphenacodon

EARLY SYNAPSIDS

Spines from Edaphosaurus’s fin

Edaphosaurus skeleton Edaphosaurus’s skeleton shows it had a relatively deeper tail andshorter limbs than Dimetrodon.

Tall, rod-shaped boneswith short crosspiecesheld up Edaphosaurus’sskin fin, or sail.

TWO TYPES OF TEETH


nSKIN SAILThe skin sail rising from Dimetrodon’s back was


197197

Triassic 250–203 295–250 Jurassic 203–135 Cretaceous 135–65 Tertiary 65–1.75 Quaternary 1.75–present

MESOZOIC 250–65 MYA CENOZOIC 65 MYA–present






TWO TYPES OF TEETH


EARLY SYNAPSIDS






197197

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Palaeogene 65.5–23 Neogene 23–present







EARLY SYNAPSIDS




TWO TYPES OF TEETH


326 327

COMPARATIVE DATINGTO FIT A FOSSIL into the wider picture ofprehistory, palaeontologists must know howold it is. In most cases, they work this out bystudying its relationship to surrounding rocksand other fossils. Fossils only form insedimentary strata – accumulated layers ofrock formed by layers of compressedsediment. More recent strata, normally thoserelatively closer to the surface, will naturallycontain younger fossils. Some fossils can alsobe important dating tools themselves – theycan display distinctive changes in shape andstructure over comparatively short timescales.Changes in fossils found within rock stratadivide the part of the geologicaltimescale covered in this book intothree great eras, subdividedinto periods.

INDEX FOSSILSScientists subdivide the geologicaltimescale into many units: aeons, eras,periods, epochs, ages, and zones. Azone is a small unit of geological time,defined by the evolutionary history ofcertain organisms, known as indexfossils. The most useful index fossils areorganisms that evolved rapidly and spreadwidely so they define a limited time zoneover a large geographical area. Commonfossils, such as ammonites, brachiopods,and trilobites are used as index fossils.They are widely distributed and areeasily recovered from marinesediments, and they show enoughvariation over time to provide easilyrecognizable chronological markers.

BIOSTRATIGRAPHYGeological changes mean that a stratigraphic “column”does not always reflect a neatchronological sequence. Fossilsof established age found in the rocks can be vital inestablishing the history andcurrent arrangement of thestrata. They can also help toestablish links between stratafrom very different localities, a process known as correlation.By matching and comparingrock and fossil samples fromdiverse locations, geologistshave been able to devise ageneral stratigraphic history.

MICROFOSSILS AS DATING TOOLSThe smallest of fossils can also be

used as index fossils. They areparticularly useful for datingrocks that have been recovered

from boreholes such as thoseused in oil exploration. A very

narrow rock core can yield a largenumber of useful fossils. Datingrocks and correlating finds betweenboreholes is a vital tool in findingand recovering mineral wealth from great depths.

COMMON INDEX FOSSILSIndex fossils are used to date rocks on aworldwide basis. A number of distinctiveorganisms are closely associated withdifferent geological periods. Trilobites are used for dating in the Cambrian,graptolites in the Ordovician and Silurian,ammonites and belemnites in the Jurassicand Cretaceous. Microfossils becomeimportant in the Mesozoic era, and smallunicellular fossils called foraminiferans are used in the Cenozoic. In some periods, such as the Triassic, index fossils are rare because of alack of marine sediments. The history of theseperiods is therefore particularly hard to decipher.

STUDYING STRATAUnconformities (breaks in a layered sequence of rocks)complicate the structure of rock strata, but also giveimportant clues to geological history. An unconformity is an old, buried erosion surface between two rockmasses, such as where a period of uplift and erosiononce removed some layered rock before the build up of sediment resumed.

REFERENCE SECTION COMPARATIVE DATING

A missing layer of stratashows a gap in sedimentation,perhaps caused by a fall in water level.

Eroded outcropof igneous rock

Parallelunconformity

Disconformity – anirregular, eroded surfacebetween parallel strata

Disconformity showswhere a riverbedonce ran.

Dyke of igneousrock intrudinginto older strata

Angular unconformity –rocks below tilt atdifferent angles fromthose above.

This unconformity isthe eroded surfaceof folded strata,once mountaintops.

Cretaceousbelemnite

Unconformity

Limestone containingEocene Alveolina fossils

STRATIGRAPHYThe examination of rock strata, called stratigraphy, is a vitaltool for interpreting Earth’s history. The basic principle ofstratigraphy is that younger rocks are deposited on top ofolder ones – but unfortunately strata do not always lieneatly on top of each other in the order in which theyformed. Continental drift and mountain building fold,fault, and contort rock strata, sometimes turning themcompletely upside down. Changing sea levels can accelerateor halt the build up of sediments, and upwelling moltenrocks can also disrupt the sediments. Any interruption tothe steady sequence of strata is called an unconformity.

Derbiya –Carboniferousto Permian

Sediments aboveunconformity indicatethat it was under water –perhaps in a riverbed.

Ordovician graptolite

Early Jurassic ammonites

Palaeocene nummulite microfossils

Fossil brachiopods

Pleuropugnoides –Carboniferous only

LAND ANIMALS

286 287

DEVONIAN PERIOD

LIMBS ON LANDThe Devonian was one of the mostimportant periods of vertebrateevolution. The first vertebrates with four limbs and distinct digits evolvedfrom lobe-finned fish during this time,and by the Late Devonian they had spread widely around the world.Land-living arthropods increased innumber throughout the period.Primitive, wingless insects and evenwinged forms arose while spiders andtheir relatives became more diverse.

ACANTHOSTEGAAmong the earliest offour-limbed vertebrates wasAcanthostega from Greenland.Like its lobe-finned fish relatives, itwas a pond-dwelling predator that still had gillsand a paddle-like tail. Its limbs suggest that it would not have beengood at walking on land. However, fossilized tracks show that somefour-footed vertebrates had ventured onto land by this time.

Zosterophyllumllanoveranum

REFERENCE SECTION FOSSIL TIMELINE

EARTH FACTS

The Devonian world was warm andmild. The huge continent Gondwanalay over the South Pole while modernEurope and North America werepositioned close to the equator. Sealevels were high, and much of theland lay under shallow waters, wheretropical reefs flourished. Deep oceancovered the rest of the planet.

ICHTHYOSTEGA FOSSILIchthyostega was an early four-footedvertebrate. It probably hunted fish and

other prey in shallow pools. Features of itslimbs suggest that it was relatively advanced

and was related to the ancestor of all later four-footed vertebrates. Ichthyostega had a short,

broad skull and very broad ribs, which helpedsupport its body when it crawled on land.

EASTMANOSTEUSPlacoderms were jawed fish that were

abundant in Devonian seas. Theyincluded predators, armouredbottom-dwellers, and flattened ray-like forms. Some Late Devonianplacoderms reached 10 m (33 ft)in length, making them thelargest vertebrates yet to evolve.

Eastmanosteus, known fromAustralia, North America,

and Europe, was less than 2 m (6 ft 6 in) long butwould still have been

a formidable hunter.

LEAVES AND ROOTSThe Devonian Period saw the mostimportant steps so far in thedevelopment of land plants. Leavesand roots evolved independently in a number of different groups. Forthe first time, plants displayedsecondary growth – their stemscould not only grow in length, butalso in diameter. Thesedevelopments allowed plants togrow far larger than before. Theearly reed-like pioneers on landgave way to gigantic trees andspecies with complex leaves.Horsetails, seed ferns, andconifer ancestors appeared latein the Devonian, and it was theseforms that would evolve intospecies that later made up the lush forests of the Carboniferous.

ARCHAEOPTERISThis widespread and highly successful

Late Devonian plant was one of thefirst to resemble modern trees. Ithad an extensive root system and itstrunk had branches with reinforcedjoints at its crown. Archaeopteris wasalso one of the first plants to reachgreat size, reaching about 20 m (65ft). Scientists once thought that itswoody trunk belonged to a differentspecies and named it Callixylon.

Clusters ofspore-bearingstems

Sharp teethsuggest a diet of fish and otheranimals

Pointed fins with aprominent central row of bones.

Branching, fern-like leaves

Limbs served asprops for walkingon land.

PHACOPSThis smalltrilobite lived inwarm, shallow seas.Like many arthropods,each of its body segmentssupported two sets of limbs.For protection against predators itcould roll up its body and tuck itstail beneath its head. Seven of theeight groups of trilobites, includingthe one to which Phacops belonged,died out at the end of the Devonian.

Large eye forexcellent vision

Phacops

Seven toes on each foot

Ichthyostega

Archaeopteris

DEVONIAN DIVERSITYHeavily armoured jawless fishflourished in the Devonian seasand jawed fish were by now alsoabundant. Among the bonyfishes, lobe-finned fish werenumerous and diverse while ray-finned fish began to become moreimportant. Several groups oftrilobites were still widespread andammonoids and modern-typehorseshoe crabs appeared. Theirdescendants survive to this day.

DIPTERUSLungfish such

as Dipterus wereone of the most

abundant groups of the Devonian.Five species of these lobe-finned fish

survive in modern times. Dipterus swam inEuropean waters and, like all lungfish, had large

crushing teeth. Fossilized stomach contents show that it waspreyed on by placoderms.

ZOSTEROPHYLLUMLacking roots andleaves, Zosterophyllum was a primitive land plant.Its erect, branching stems grew not from roots,but from a complex underground rhizome(stem). The sides of the stems carried smallkidney-shaped capsules in which spores wereproduced. Reaching a height of around 25 cm (10 in), the plant probably grew along the swampy edges of lakes.

416–359.2MYA

GONDWANA

AQUATIC ANIMALS

LAND PLANTS

EURAMERICA

352 353

REFERENCE SECTION BIOGRAPHIES

Leading expert on dinosaurtrackways, professor of geologyat the University of Colorado,and curator of the DenverFossil Footprint Collection.Lockley’s primary researchinterests include fossilfootprints, dinosaur trackways,and palaeontological history.His research has taken himfrom his home bases ofColorado and Utah to Europe,and Central and East Asia.

WILLARD LIBBY1908–80

MARTIN LOCKLEYBORN 1950

English naturalist and geologistwho catalogued the fossilmammals, reptiles, and birds inthe British Museum. Lydekker’smagnificent 10-volume set of Catalogues was published in 1891. In 1889, he published the two-volume A Manual ofPalaeontology together with H.A.Nicholson. Lydekker was alsoresponsible for naming thedinosaur Titanosaurus (1877).

MARY AND LOUIS LEAKEY

A husband and wife team whose fossil findsproved that human evolution was centred

on Africa, and that the humanspecies was older than hadbeen thought.

STANLEY MILLER1930-2007

American chemist who conductedexperiments in the 1950s to demonstrate the possible origins of life on Earth.

While working in Chicago in 1953, the 23-year-oldMiller passed electrical discharges – equivalent to asmall thunderstorm – through a mixture of hydrogen,methane, ammonia, and water, which he believedrepresented the constituents of Earth’s earlyatmosphere. After some days, his analysis showed the presence of organic substances, such as aminoacids and urea. Miller’s experiments revolutionizedscientific understanding of the origins of life on Earth.

CAROLUS LINNAEUS1707–78

RICHARD LYDEKKER1849–1915

Scottish barrister and geologistwho studied the geology ofFrance and Scotland, and in1827 gave up a career in law fora life spent studying geology. Inhis work The Principles of Geology(1830–33), Lyell devised thenames for geological epochsthat are now in universal usage,including Eocene and Pliocene.His Elements of Geology, whichwas published in 1838, becamea standard work on stratigraphyand palaeontology. In Lyell’sthird great work, The Antiquityof Man (1863), he surveyed thearguments for humans’ earlyappearance on Earth, discussedthe deposits of the last Ice Age, and lent his support toDarwin’s theory of evolution.

CHARLES LYELL1797–1875

American palaeontologist whoworked extensively on the fossilrecord of mammals. Matthewwas curator of the AmericanMuseum of Natural Historyfrom the mid-1890s to 1927.One of his key theories, thatwaves of faunal migrationrepeatedly moved from thenorthern continents southward,mistakenly relied on the notionthat the continents themselveswere stable. Matthew also did early work on Allosaurusand Albertosaurus, and on theearly bird Diatryma. He namedDromaeosaurus in 1922. He was one of the first to study theeffect of climate on evolution.

German palaeontologist who named and describedArchaeopteryx (1861),Rhamphorhynchus (1847),and Plateosaurus (1837). Meyerwas one of the first to viewdinosaurs as a separate group,which he called “saurians” in 1832. Meyer startedpublication of the journalPaleontographica in 1846, andused it to publish much of hisresearch on fossil vertebrates.

American palaeontologist andpioneer of dinosaur studies.Marsh described 25 new generaof dinosaurs and built up oneof the most extensive fossilcollections in the world. After studying geology andpalaeontology in Germany,Marsh returned to America and was appointed professor ofpalaeontology at Yale Universityin 1860. He persuaded hisuncle, George Peabody, toestablish the Peabody Museumof Natural History at Yale. Onscientific expeditions to thewestern United States, Marsh’steams made a number ofdiscoveries. In 1871, they foundthe first American pterosaurfossils. They also found theremains of early horses in the USA. Marsh described the remains of Cretaceoustoothed birds and flyingreptiles, and Cretaceous andJurassic dinosaurs, includingApatosaurus and Allosaurus.

OTHNIEL CHARLESMARSH1831–99

WILLIAM DILLERMATTHEW1871–1930

HERMANN VON MEYER1801–69

American chemist whosemethod of radiocarbon dating proved an invaluabletool for palaeontologists andarchaeologists. As part of theManhattan Project (1941–45),Libby helped to develop amethod for separating uraniumisotopes. In 1947, he discoveredthe isotope Carbon-14. Itsdecay within living organisms isused to date organic materials,such as shell and bone. Libbywas awarded the Nobel Prizefor Chemistry in 1980.

American scientist who wasprofessor of anatomy at theUniversity of Pennsylvania. Awell-respected anatomist and aspecialist on intestinal parasites,Leidy became famous as avertebrate palaeontologist. He examined many of thenewly discovered fossil findsfrom the western states and, ina series of important books andpapers, laid the foundations ofAmerican palaeontology. HisExtinct Fauna of Dakota andNebraska (1869) containedmany species unknown toscience and some that werepreviously unknown on theAmerican continent.

An Italian dinosaur expert who became a palaeontologistwhile studying to become apriest. Leonardi travelled toBrazil in the 1970s in search ofmeteorites, and later returnedthere to live. He has travelledto the most remote terrain inSouth America in search ofdinosaur tracks from differentperiods. He also discoveredwhat may be one of the world’soldest tetrapod tracks, datingfrom the Late Devonian. Hehas mapped remote sites ininaccessible locations, and has synthesized informationabout fossilized footprints on a continental scale.

JOSEPH LEIDY1823–91

GIUSEPPE LEONARDIDATES UNAVAILABLE

Louis Leakey (1903–72) was born in Kenya of Englishparents. In 1931, he began work in the Olduvai Gorge,Tanzania, aided by his second wife, Mary (1913–98),an English palaeoanthropologist. In 1959, Marydiscovered a 1.7-million-year-old fossil hominid, nowthought to be a form of australopithecine. Between1960 and 1963, the Leakeys discovered remains of Homo habilis, and Louis theorized that their find was a direct ancestor of humans.

Stanley Miller with the glass apparatusused to recreate theconditions found on primitive Earth.

CarolusLinnaeus

Swedish botanist whose Systema naturae(1735) laid the foundations for theclassification of organisms.

Linnaeus was the first to formulate theprinciples for defining genera andspecies. He based a system of classification on his closeexamination of flowers. Thepublication of this system in 1735 was followed by the appearance of GeneraPlantarum (1736), a work that is considered the startingpoint of modern botany.

The Leakeys holda 600,000-year-old skull found inTanzania, CentralAfrica.

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REFERENCE PAGESThe large reference section providesinformation on how scientists use fossils tounderstand the past. It begins with a fossiltimeline, and then describes variouspaleontological processes, such as the datingand reconstruction of fossil animals. Thissection includes tips for the amateur fossilhunter and biographies of leading scientists.A glossary with a pronunciation guideexplains terms used throughout the book.


Annotation text in italicsexplains interesting details in photographs and artworks.

TIMELINE BARAt the foot of the animal andfeature pages is a timeline bar thatshows the geological time periodsand eras covered throughout thebook. The colored parts of the barhighlight the period and era inwhich the main animal featured inthe entry lived.

A geography box with a global mapdescribes what theEarth was like duringa particular period.

FOSSIL TIMELINEA fossil timeline featureruns for 34 pages in thereference section, andprovides a period-by-periodlook at prehistoric life.

This bar highlightsthe era in whichDimetrodon lived.

Referencepages explainpaleontologicalconcepts andmake them easyto understand.

Each timeline pagecontains sampleimages of the plant and animal life presentduring a certain period.

Biographyentries givedetails aboutinfluentialscientists andpalaeontologists.

FACT BOXThe fact box provides a profile of the maincreature featured in ananimal entry. A graphicscale compares the size ofthe animal with a 5-ft 8-in(1.7-m) tall man. Quick-reference facts providespecific information,including the creature’sscientific name, size, diet,and habitat. The place or places in which fossils of the creature werediscovered is also given.The period in which it lived and its relatedgenera are the final two entries. The box header often contains a translation of the animal’s scientific name.

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LIFE ON EARTH is almostinfinite in its variety – plants,animals, and other forms oflife surround us in a multitudeof forms. Ever since peoplefirst realized that fossils arethe remains of once-livingthings, they have strived tointerpret them. Paleontology,the study of ancient life,involves reconstructing theformer appearance, lifestyle,behavior, evolution, andrelationships of once-livingorganisms. Paleontologicalwork includes the collection of specimens inthe field as well as investigation in thelaboratory. Here the structure of the fossil,the way it is fossilized, and how it compareswith other forms are studied. Paleontologyprovides us with a broad view of life on Earth.It shows how modern organisms arose, andhow they relate to one another.

EARLY FINDS AND THEORIESPeople have always collected fossils. In some cultures,elaborate myths were invented to explain these objects.For example, ammonites, extinct relatives of squids, were thought to be coiled snakes turned to stone.Paleontology as we recognize it today arose in the late 18th century. The discovery of fossil mastodons(American relatives of elephants) and of Mosasaurus, a huge Cretaceous marine reptile, led to the acceptanceof extinction, an idea previously rejected as contrary tothe Bible. With the concept of extinction and life beforeman established, scientists began to describe remarkableforms of life known only from their fossilized remains.

FINDING OUT ABOUT THE PAST


Discovery of Mosasaurus

DIGGING UP FOSSILSTo discover fossils, paleontologists do not generally go out and dig holes. Most fossils are found when they erode onto thesurface, so places where there is continual erosion of rock bythe wind and water are frequently good sites. Expeditions tosuitable locations may involve expensive journeys to regionswhere travel is difficult. Excavators once dug out fossils withlittle regard for the context in which they were found. Todaywe realize that such information is important. The sedimentarylayer in which a fossil is found, and its relationship with otherfossils, can reveal much about its history prior to preservation.

Paleontologists at work in Mongolia

THE STUDY OF DEATHTaphonomy is the branch of paleontology concerned with the study of how organisms died and what happened to theirbodies between death and discovery. It reveals much aboutancient environments and the processes that contribute tofossilization. A fossil’s surface can show how much time went by before the dead animal was buried. This may explain its state of preservation and why parts of it are missing. Fossils also preserve evidence of their movements after death – they may be transported by water or moved around by animals.

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RECONSTRUCTING THE PASTHow do paleontologists produce reconstructions of prehistoricenvironments, like the Carboniferous swamp forest shown here?Studies on modern environments show that distinct kinds of sedimentare laid down in different environments. Many living things inhabitcertain habitats, and the physical features of a fossil may also showwhat environment it favored when alive. Using these clues,paleontologists can work out what kind of environment a fossildeposit represents. Fossils themselves may reveal features thatshow how they lived. Interactions between fossils, such as preserved stomach contents and bite marks, aresometimes preserved. Using all of these pieces ofevidence, paleontologists can piece togetherenvironments andecosystems thatexisted in the past.

Weak limbs, sensory skullgrooves, and the position of itseyes and nostrils suggest thatthe temnospondyl Eryops and

its relatives were water-dwelling predators.

Meganeura’s wings recallthose of dragonflies, suggestingthat it was a fast-flying predator.It probably hunted other insectsover the Carboniferous pools andlakes. Fossils of Meganeura andrelatives of Eryops are all foundfossilized within Carboniferouscoal deposits.

Preserved Lepidodendron trunksreveal that this giant clubmossgrew up to 160 ft (50 m) tall,dominating the vegetation in and around large swamps. Treessuch as Lepidodendron formed the huge coal deposits that givethe Carboniferous its name.


Trunk ofLepidodendron

FossilMeganeura

Skeleton of Eryops

1212

FOSSILSNATURALLY PRESERVED REMAINS of once-living organisms, or the traces they made, are called fossils. These objects usuallybecome fossils when they are entombed in sedimentand later mineralized. Fossils are abundantthroughout the Phanerozoic Eon – the ageof “obvious life” from 542 million yearsago to the present, so called because of its plentiful fossil remains. Thousands offossil species, from microscopic organismsto plants, invertebrates, and vertebrateanimals, are known from this time. Earlierfossils are revealed by distinctive chemicaltraces left in rocks as well as fossilizedorganisms themselves. These extend backin time some 3.8 billion years, to when ourplanet was young. Because most deadorganisms or their remains are usuallybroken down by bacteria and otherorganisms, fossilization is relatively rare.Even so, billions of fossils exist.

TYPES OF FOSSILThe remains of plants and animals (such as shells,teeth, bones, or leaves) are the best known fossils.These are called body fossils. Traces left behind byorganisms – such as footprints, nests, droppings, orfeeding marks – may also be preserved as fossils,and are called trace fossils. These are often the mostabundant kinds of fossil but, unless they arepreserved alongside the organism that made them,they are often hard to identify precisely.

Riverbeddepositssediment on skeleton

Animal dies anddecomposes ina riverbed.

FOSSILS

Theropod trackway

Fossilized Saltasaurusosteoderm (skin)

Plates may havehelped protect thedinosaur frompredators.

This armor platecomes from asauropod dinosaur.

Rocks are condensedlayers of sedimentssuch as sand or mud.

When these trackswere formed, thisrock surface wassoft mud.

A skeletonburied bysediment isprotected fromscavengers onthe surface.

These three-toedtracks were probablymade by predatorydinosaurs.

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HOW FOSSILS FORMThe most common form of fossilization involves theburial of an organism, or an object produced by anorganism, in sediment. The original material fromwhich the organism or object is made is then graduallyreplaced by minerals. Some fossils have not formed inthis way. Instead, the original object has been destroyedby acidic groundwater, and minerals have later formed a natural replica of the object. Both processes take along time, but experiments have shown that fossils canbe formed much more quickly. In these cases, mineral

crystals form in the tissues shortly afterdeath, meaning that they start to fossilizewithin a few weeks – before decompositionhas set in. This type of fossil can preserveblood vessels, muscle fibers, and even

feathers in exceptionalconditions.

Once exposed, a fossilmay be discovered bypeople.

Erosion at the surface of theEarth means that new fossilsare constantly being revealed.

FOSSILS

Minerals in thegroundwater maychange the fossil’scomposition.

More sediments deposited abovethe fossil bury it deeper in the rock,and may compress or distort it.

Moving continentalplates may carrysediments far fromtheir original location.

Many exposedfossils are destroyedby the action ofwind and water.

EXCEPTIONAL FOSSILSThe soft parts of organisms are usually lost beforefossilization begins, as they are broken down quickly bybacteria and other scavengers. For this reason soft-bodied animals (such as jellyfish or molluscs) are poorlyrepresented in the fossil record. However, rapid burialin soft sediment, combined with the presense of certainspecial bacteria, can mean that soft parts are retainedand fossilized. The complete remains of soft-bodiedorganisms can be preserved under such conditions, ascan skin and internal organs.

Fossilized hedgehog Pholidocercus

RESULTS OF FOSSILIZATIONFossils that are composed of new,replacement minerals are harder,

heavier versions of the original. Theyalso usually differ in color from the

object that formed them. Thisammonite fossil is gold because it is

composed of iron pyrite, the mineraloften called “fool’s gold.” Due to

pressure inside the rock, fossils may also be altered in shape. Some fossilscan be so distorted that experts have

difficulty imagining their original shapes.

Bacteria and otherscavengers underground may stilldestroy the skeleton.

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VENDIAN LIFEThe fossilized remains of Vendianfauna (Precambrian

organisms) were firstfound at Ediacara Hill in

South Australia. This formation, composed of unusual disk- andleaf-shaped fossils such as the Mawsonites pictured, provided thefirst glimpse of the earliest multi-cellular life forms. Vendianfauna vaguely resembled later creatures, for example Sprigginalooks like a worm while Charniodiscus resembles a sea pen. Somepaleontologists believe that the Vendian fauna includes theearliest members of several animal groups, but the fossils aregenerally too incomplete to prove this beyond doubt. Anothertheory is that Vendian organisms were an independentdevelopment in eukaryotic life, unrelated to later organisms.

FIRST LIFEThe earliest forms of life were prokaryotes.These small, single-celled lifeforms carried

DNA, a chemical that codes geneticinformation, loosely within their cellwalls. Prokaryotes developed a wide

range of different metabolisms(chemical reactions to generate energy)

that may well have helped to produce a planet more suited to advanced

lifeforms. Prokaryotes form two groups –bacteria and archaea. Many thrive in

environments that more advanced life formswould find inhospitable or poisonous, such ashot springs and muds devoid of oxygen. Hugefossilized mats of prokaryotic cells are calledstromatolites – they show how widespread anddominant these organisms were early on in Earth’s history.

EVOLVING LIFE

JellyfishlikeMawsonites

Undulipodium(tail) forpropulsion

Nucleus containsmany strands of DNAand huge amounts ofgenetic information.

ORIGIN OF EUKARYOTESComplex eukaryote cells seem to have developed from differentkinds of more simple organisms that took to living together andthen functioning cooperatively. This cooperation is calledsymbiosis. Eukaryotes have a central nucleus containing theirnucleic acids, such as DNA, and many structures called organellesscattered throughout their fluids. Different organelles havedifferent functions – most are involved in creating energy to fuelthe organism itself. Multicellular organisms, probably evolvingfrom single-celled eukaryotes, arose in the Late Precambrian. A great growth of complex lifeforms then took place.

THE FOSSIL RECORD PRESERVES the history oflife from the earliest single-celled organismsto the complex multicellular creatures –including plants, fungi, and animals – ofmore recent times. It shows that simplesingle-celled forms of life called prokaryotesappeared very early on in the history of ourplanet – traces of microscopic life have beendated to around 3,800 million years ago.More complex, though still single-celled,organisms appear in the fossil record about2,000 million years ago. In these cells, calledeukaryotes, genetic information is stored in a structure called the nucleus. Eukaryoticorganisms include algae, plants, fungi, andmany other groups. In the Late Precambrian(around 600 million years ago), the firstmulticellular eukaryotes, or metazoans,arose. By the Cambrian (542–488.3 millionyears ago), these metazoans had diversifiedinto a multitude of animals.

EVOLVING LIFE

Flagellum (tail)for propulsion

DNA

Cell wall

Mitochondrion –organelle thatmakes energy by respiration

Ribosomesproduceproteins thatform the cell.

Structure of aeukaryotic cell

Plastid –organelle thatmakes energy byphotosynthesis

Charniodiscus

Fossil Mawsonites

Fossil stromatolite

Artist’s restoration of Vendian life

Ribosomesproduce proteinsthat form the cell.

15

THE BURGESS SHALEThe Burgess Shale of British Columbia, Canada, is a famous rock unitcomposed of layers of fine-grained siltstone deposited on the floor of ashallow Cambrian sea. Discovered in 1909 by American paleontologistCharles Walcott, it contains thousands of well-preserved animal fossils,including early members of most modern metazoan groups, as well asother animals that became extinct shortly afterward. The BurgessShale gives a unique insight into the “Cambrian Explosion” of life.Arthropods, worms, early chordates (relatives of vertebrates), andmembers of severalother groups, manypreserved with softparts intact, are allfound here.

METAZOAN DIVERSITYThe Burgess Shale shows how well metazoans diversified to fill the available ecological niches.The rest of the Phanerozoic Eon (theage of “obvious life”) saw increasingdiversification of these groups, theinvasion of the land, and a boom in thenumbers and variety of arthropods andvertebrates. Animals invaded the air, spreadthough freshwater environments, andcolonized all environments on land.Mollusks and vertebrates have grown to bethousands of times larger than the earliestmetazoans. Single-celled organisms, however, havenot waned in importance or diversity. Bacteria arepresent worldwide in all environments, and faroutnumber metazoans, so today could still be regarded as part of “the age of bacteria.”

EVOLVING LIFE

Pikaia was an earlychordate. It was awormlike swimmer with tail fins.

Anomalocaris was agiant among BurgessShale animals, growingto 24 in (60 cm) long.

Anomalocaris was a largepredatory arthropod witha circular mouth,grasping appendages,and swimming fins along its sides.

Hallucigenia was originallyreconstructed upside-down – the defensivespikes were thought to belegs. The fleshy legs werethought to be feedingtentacles.

Sponges grew onthe floor of theBurgess Shale sea,but the reefs of thetime were mostlyformed by algae.

Hallucigenia was probably a bottom-dweller that fed on organic particles.

Priapulids are burrow-dwelling worms. Today theyare rare, but in Burgess Shaletimes they were abundant.

Marrella was a tinyswimming arthropod.It was probablypreyed on by manyof the Burgess Shale predators.

Spiky lobopods likeHallucigenia were distantrelatives of arthropods.

MammalBirdDinosaur

Arthropod

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HOW EVOLUTION HAPPENSALL LIVING THINGS CHANGE, OR EVOLVE, over generations.This fact can be seen in living populations of animals,plants, and other living things, as well as in fossils. As organisms change over time to adapt to newenvironments or ways of life, they give rise to new species.The inheritance of features by a creature’s descendants isthe main component of evolutionary change. Anunderstanding of how evolution happens proved to beone of the key scientific revelations in our understandingof life, and understanding evolution is the key tointerpreting the fossil record. By studying evolutionarychanges, biologists and paleontologists reveal patterns that have occurred during the history of life.

EVOLUTION IN ACTIONSome living animals provideparticularly clear examplesof evolution in action. Onthe Galápagos Islands,different kinds of gianttortoises have become suited for different conditions.Tortoises on wet islands where plant growth is thick on the ground have shells with a low front opening.For tortoises on dry islands there is no vegetation onthe ground - instead they have to reach up to chew on branches that grow well above ground level. Overtime, those tortoises with slightly taller front openingsin their shells were better able to reach the highervegetation. This allowed them to better survive andpass on their genes, so now all the tortoises on dryislands have a tall front opening to their shells.

VOYAGE OF THE BEAGLECharles Darwin developed his theory ofevolution by natural selection following histravels as ship’s naturalist on HMS Beagle duringthe 1830s. Darwin studied fossil South Americananimals as well as living animals on theGalápagos Islands. The similarities anddifferences that Darwin saw made him realizethat species must have changed over time.Darwin was not the only person to propose theidea of evolution, but his ideas were the mostinfluential. His 1859 book, On the Origin of Speciesby Means of Natural Selection, is one of the mostfamous scientific books ever written.

Tortoises on dry islandshave to reach up tofind food.

Tortoises on wetislands only need toreach down to theground to find food.

HOW EVOLUTION HAPPENS

Fishing aboard the Beagle

Low front of shelloriginally shared by allGalápagos tortoises

Higher front of shellselected in dryisland tortoises.

THE THEORY OF EVOLUTIONThe theory that living things change to better suit theirenvironments was first presented by British naturalist CharlesDarwin (1809-1882). Darwin argued for the idea of slow changesto species over time, brought about by selection acting on naturalvariation. Natural variation is present in all living things - allindividuals differ from one another in genetic makeup, andtherefore in their anatomy and behavior. Natural selection is themechanism that chooses one variation over another. Allindividuals compete among themselves and with other organismsfor food and territory, and struggle to avoid predators and surviveextremes of climate. Those best at passing on their genes – inother words surviving, finding a mate, and raising offspring – willhave their features inherited by future generations.

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EVOLUTION BY JUMPSThe old view that evolution is a slow and continuousprocess has been challenged by evidence from thefossil record. Many species seem to stay the same for long periods of time, and then are suddenlyreplaced by their apparent descendants. This type of evolution is called quantum evolution. Theopposite idea, that evolution occurs as slow andgradual change, is the traditional view. It now seemsthat both kinds of evolution occur, depending on

the circumstances. When conditions stay thesame, species may not need to change but,

if conditions change rapidly, species may need to change rapidly as well.

DERIVED CHARACTERSScientists reveal evolutionary relationships by lookingfor shared features, called “derived characters.” Thepresence of unique derived characters seen in onegroup of species but not in others shows that all thespecies within that group share a common ancestor.Such groups are called clades. In the cladogram shown here, humans and chimpanzees share derivedcharacters not seen in orangutans. Humans andchimpanzees therefore share a common ancestor thatevolved after the common ancestor of orangutans,chimpanzees and humans. Orangutans, chimpanzees,and humans all share derived characters not seen inother primates and also form a clade. The field ofmolecular biology has shown that closely related species have similar protein and DNA sequences. Suchsimilarities can also be used as derived characters.

HOW EVOLUTION HAPPENS

Fossil humans appear inthe Pliocene. Chimpanzeesmust also have evolved atthis time. Chimpanzees and

humans share anenlarged canal in thepalate not seen inorangutans.

Gar fish demonstrate quantumevolution – the last time theychanged was more than 60million years ago.

All great apes(hominids) have anenlarged thumb andother derivedcharacters.

Canal passingthrough palate in upper jaw.

Long opposable thumbgives apes and humansan evolutionaryadvantage.

Horned dinosaurs like Triceratops demonstrategradual evolution. They were constantly evolving– a genus typically lasted 4–6 million years.

HUMANCHIMPANZEE

ORANGUTAN

Enlarged palatecanal

Largeopposable

thumb

DEVELOPING THE THEORYWhen Darwin put forward his theory, he was unable to propose an actual mechanism by which characteristics could pass from one generation to the next. It was severaldecades before the new science of genetics – the study ofinheritance – provided the missing piece of the puzzle andconfirmed Darwin’s ideas. More recent advances in geneticsand paleontology have shown just how complex therelationships between living and fossil species are. Evolution is not as simple as was once thought – for example, organismsdo not generally evolve in simple ladder- or chainlikeprogressions (once a popular image in books). Instead, as new species evolve from old ones, they tend to branch out and diversify, forming complex bush-like patterns. In fact, the main theme of evolution seems to be diversification.Evolution was also traditionally regarded as the developmentof increasing complexity, but this is not always true. Someliving things have become less complex over time, or have lost complicated structures present in their ancestors.

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PEOPLE HAVE ALWAYS CLASSIFIED LIVING THINGS as a way ofunderstanding the world. Organisms could be groupedtogether based on how they looked, how they moved, or what they tasted like. With the advent of science after theMiddle Ages, biologists realized that living things should begrouped together according to common features of theiranatomy or habits. However, the concept of evolution wasmissing from these systems of classification – groups werethought to correspond to strict plans created by God. In the1960s, biologist Willi Hennig argued that species should onlybe grouped together when they shared newly evolvedfeatures called derived characters. Groups of species unitedby derived characters, and therefore sharing the same singleancestor, are called clades. This new classification method,called cladistics, has revolutionized biology and palaeontology.

LINNAEAN CLASSIFICATIONThe Swedish botanist Carl von Linné (better known by thelatinised version of his name, Carolus Linnaeus) was the mostinfluential person to classify organisms in the traditional way. In 1758, he organised all living things into a grand scheme ofclassification called the Systema Naturae. Linnaeus recognized thatthe basic unit in biology was the species, and he developed anintricate system for grouping species together in increasinglybroader groups. Related species were grouped into genera,genera were collected in families, families within orders, ordersin classes, classes in phyla, and phyla within kingdoms.

THE TREE OF LIFENineteenth-century scientists thought all livingthings were part of a ladder-like scheme withhumans as the most “advanced” creatures at thetop. They classified organisms in a way thatreflected this, but this inaccurate view does notreflect the real branching of evolution. Also,evolution does not necessarily result in overall“improvement” but, instead, enables organismsto better cope with their immediate conditions.

CLASSIFYING LIFE

Jaguar

Leopard

CLASSIFYING LIFE

WHAT IS A SPECIES?The species is the fundamentalbiological unit – a populationof living things that all lookalike, can all interbreed witheach other, and cannotinterbreed with other species.There are many exceptions tothis definition – some speciescontain individuals that differradically in appearance, andsome can successfullyinterbreed with others.However, the definition holdstrue for the majority. Closelyrelated species are groupedinto genera (singular: genus).Leopards and jaguars, shownhere, are closely related speciesthat both belong within thesame genus.

NATURAL AND UNNATURAL GROUPSDuring the twentieth century, it became clear that many of the groupsused in the Linnaean system did not correspond to true evolutionarygroups because they sometimes excluded many of their own descendants.The Linnaean group Reptilia, for example, was supposed to include theancestors of birds, but not the birds themselves. So Linnaean groupswere not true natural groups, but artificial groupings created by people.Intermediate forms were also a problem for the Linnaean system –should a bird-like reptile be included in the reptile class or the bird class?Cladistics gets round these problems by only recognising natural groupswhose members all share the same ancestor. Such groups are calledclades. In the cladistic system, birds are a clade, butare themselves part of the reptile clade.

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THE CLADISTIC REVOLUTIONBy determining the sequence in which their derivedcharacters arose, scientists can arrange species in theorder that they probably evolved. However this does not allow them to recognize direct links betweenancestors and descendants. When scientists groupspecies into clades, they have to identify and describethe derived features shared by the group. This allowsother scientists to examine and test theories about the evolution of a clade – before the introduction of cladistics, this was often not the case. In collectinginformation on characters, and determining whetherthey are derived or primitive, scientists amass vastquantities of data that are analysed with computers.Cladistic studies have shown that some traditionallyrecognised groups really are clades, while others are not.

CLADOGRAMSCladograms are diagrams that representthe relationships between differentorganisms. The more derived characterstwo species share, the closer they will beon the cladogram. Cladograms do notshow direct ancestor-descendantsequences but instead portray thebranching sequences that occurredwithin groups. Branching events in thecladogram are marked by nodes – pointswhere a new derived character appears,uniting a narrower, more recently evolvedclade. In the section of a bird cladogramshown here, all three groups are unitedas a clade by a prong on their quadratebone, a feature that distinguishes themfrom all other birds. Modern birds andichthyornithiforms are also united by arounded head to their humerus bone,not shared with hesperornithiforms – sothey also belong in a narrower clade.

CLASSIFYING LIFE

Highest nodeindicatesmost recentlyevolvedgroup.

Linnaean tree

AMPHIBIANS

BASALTETRAPODS

FISH

REPTILES

Cladistic classification

More advancedgroups diverge fromthe tree at later times.Reptiles, for example,diverged later thanamphibians.

Amphibians are anartificial Linnaeangroup

No advancedfeature links all fish,but they can formsmaller clades.

Primitive tetrapods do not sharederived characters with modernlissamphibians, so the Linnaean“amphibian” group is not a clade.

Reptiles all share aderived character, so area true clade.

Clades divergewhen new derivedcharacters appear.

AlligatorAcanthostega

Ray

Higher nodeindicates a laterevolutionary trait,distinguishing anarrower clade.

Node indicates the root ofa clade linked by a sharedderived character.

RAY-FINNEDFISH

REPTILES

Derivedcharacter

Derivedcharacter

Derivedcharacter

ORNITHURAEProng on quadrate

CARINATAERounded head of

humerus

HESPERORNITHIFORMS

NEORNITHESSaddle-shaped faces to

neck vertebrae

ICHTHYORNITHIFORMS

MODERN BIRDSHesperornis fromthe Cretaceous

Ichthyornis fromthe Cretaceous

Sparrow

20

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Fish and InvertebratesWater “woodlice,” some as large as serving dishes,

dragonflies with the wingspan of hawks, and sea

scorpions as big as people are all featured among

the prehistoric invertebrates (animals without

backbones) in this section. Also displayed are a

fantastic variety of fish, the first animals to have

backbones. Little jawless creatures with ever-open

mouths, armored fish with rocker jaws, spiky-finned

spiny acanthodians, and those superbly streamlined

swimmers, the sharks and bony fish, are all exhibited

here. Finally, lobe-finned fish, an ancient group that

is ancestral to humans, are featured. Throughout

the section, color photographs depict fossil

specimens, and computer models reveal how

long-dead organisms actually looked.

22

INVERTEBRATES CLADOGRAMTHE SIMPLEST ANIMALS ARE INVERTEBRATES whose bodies lack distinct leftand right sides. Cnidarians and other primitive groups do not havedefinite front ends, but their cells are organized into regions thathave specialized functions. Members of some higher groups possesshard parts – a feature that evolved in the Early Cambrian. Advancedinvertebrates have bodies with distinct left and right sides. Early in theevolution of some of these bilaterally symmetrical animals, the abilityto move forward became an advantage, and these animals evolveddistinctive head regions to house their primary sensory organs.

FISH AND INVERTEBRATES

SPONGES (PORIFERANS)

CTENOPHORES

CNIDARIANS

ECHINODERMS

CHORDATES

TWO CELL LAYERSAll animals have twolayers of cells in theirbody walls, which is thesimplest type of bodyorganization. The layersform a bag that enclosesan internal cavity.

HOLLOW-BALL EMBRYOThe development of theembryo from a hollow ballof cells is a feature not seenin sponges. Animals whoseembryos go through thehollow ball stage are able to develop more complexbodies than sponges.

THREE TISSUE LAYERSFlatworms and higherinvertebrates areunited by the presence

of three layers of tissue.These three layers allowedthe evolution of a morecomplex body, and adistinct gut and organs.

CIRCULATION SYSTEMThe presence of a systemthat circulates bloodunites deuterostomes,ecdysozoans, andlophotrochozoans.

ANUS DEVELOPMENTIn deuterostomes, theblastopore – the first hole

that forms in the embryo –becomes the anus.

Rhizopoterion

Blastopore

Hollow, fluid-filled embryo

Jellyfish

Planarianflatworm

Jurassic starfishPentasteria

Embryo

Circulation systemof a crayfish

Endoderm

Ectoderm

Ectoderm

Mesoderm Endoderm

ANIMALSTwo cell layers

Hollow-ball embryo

Three layers of tissue

Circulation system

DEUTEROSTOMESAnus develops from

blastopore

FLATWORMS(PLATYHELMINTHS)

23

MOLLUSKS ANNELIDS

LOPHOPHORATES

DEUTEROSTOMES AND PROTOSTOMESSegmentation evolved in some deuterostomesand protostomes, enabling them to devote partsof their bodies to key functions. It may also haveprovided these animals with more flexibility.

TROCHOPHORE LARVAAlthough trochozoans are diverse in appearance, they all have similar larvae –microscopic, rounded,swimming creatures with fine hairs around the middle.

MOLTINGIn ecdysozoans, the externalskeleton called the cuticle isshed as the animal grows.This shedding allowsecdysozoans to undergometamorphosis – change inbody shape during growth.

The Cambriantrilobite Elrathiais an arthropod.

INVERTEBRATE EVOLUTIONMost views about the evolution of animals come fromstudies on genetics and on the development of embryos.Fossils show that all major animal groups had evolved bythe Cambrian. Hard parts evolved suddenly in the EarlyCambrian, perhaps to function as storage sites for mineralsused in animal growth and development. Later, hard partsbecame vital external features inherited by deuterostomes,ecdysozoans, and lophotrochozoans. Not all scientists agreewith the grouping within the invertebrate cladogram, suchas putting nematodes with other ecdysozoans.

Brachiopod Cancellothyris

GastropodCampanile

INVERTEBRATES CLADOGRAM

Water bear

Earthworm

Locust molting

Cilia bandsencircle the larva.

EyespotsECDYSOZOANS

Molting LOPHOTROCHOZOANS

TROCHOZOANSTrochophore larva

ARTHROPODS

ROUNDWORMS(NEMATODES)

WATER BEARS(TARDIGRADES)

VELVET WORMS(ONYCHOPHORANS)

Centipede

PROTOSTOMESMouth and anus develop

from blastopore

24

Cambrian 542–488.3


PALEOZOIC 542–251 MYA

TRILOBITESBEFORE FISH BECAME DOMINANT, ancient seas teemed with trilobites – therelatives of living woodlice, crabs, and insects. Trilobites were among the earliest arthropods. The name trilobite, which means “three-lobed,” describes the trilobite body’s division lengthwise into three parts separated by two grooves. Most trilobites crawledacross the ocean floor, although some species swam. Theyranged in size from the microscopically tiny to species thatwere larger than a platter. With more than 15,000 species,trilobites outnumber any other known type of extinctcreature. The trilobites’ heyday occured during theCambrian and Ordovician periods, and the last species vanished during the mass extinction at the end of the Permian period.

TRILOBITE BODY PLANViewed lengthwise, a trilobite’s body, such as this Phacops(right), has a raised middle lobe, or axis, sandwiched betweentwo flatter lobes called the pleural lobes. Trilobites were alsodivided crosswise. The three main body parts consisted of thecephalon (head), the thorax, and the pygidium (tail). Therewere cheeks and eyes on either side of the head. The longthorax was made of many segments, each of which held paired limbs. A tough outer casing protected all parts of the body. After a trilobite died, the casing often broke apart into the three main lobes.

DEFENSEPhacops (“lens eye”) curled up in

a tight ball or burrowed if attacked.The 12 armored plates of its thorax

overlapped like a Venetian blind toprotect the legs and underside. Fish

were probably Phacops’s worst enemies, but trilobites that lived earlier than Phacops

feared Anomalocaris, eurypterids, and nautiloids.

A knobbly shieldguarded Phacops’s

head, and its eyes had hard

calcite lenses.

Phacops rolledup in defense

Carboniferous 359.2–299 Permian Devonian 416–359.2Silurian 443.7–416Ordovician 488.3–443.7

Pygidium(tail)

Middle lobe

Pleural lobe

25

Triassic 251–199.6 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Paleogene 65.5–23 Neogene 23–present


TRILOBITES

TRILOBITE EYESThe eyes found in trilobites wereamong the earliest animal eyes toevolve. There were two main typesof eye, each made up of tiny calcite-crystal lenses. Most trilobites hadholochroal eyes, which resembledthe compound eyes of insects. Up to 15,000 six-sided lenses were closely packed like cells in a honeycomb. Each lens pointed in a slightly different direction.Holochroal eyes formed fuzzyimages of anything that moved.Other trilobites had schizochroaleyes, which contained large, ball-shaped lenses. Schizochroal eyesproduced sharp images of objects.

CLUES TO A VANISHED OCEANTwo trilobites are clues to the existence of a long lost ocean.In Cambrian times, Olenellus and Paradoxides lived on oppositesides of the Iapetus Ocean, which was too deep for either tocross. Later, both sides of the ocean merged, then the land redivided to create the Atlantic Ocean. The new split meansthat both trilobites crop up in rocks in the same countries,but Olenellus fossils mainly occur north of the regions whereParadoxides fossils are found.

Distribution of Olenellus and Paradoxides fossils

Phacops

LENS EYE

Scientific name: PhacopsSize: 1.75 in (4.5 cm)Diet: Edible particlesHabitat: Warm, shallow seasWhere found: WorldwideTime: DevonianRelated genera: Calymene, Cheirurus

Cross-section of aschizochroal eye

Small lenses touchone another andare covered by a single cornea.

Lens transmitslight to receptorsin the eye.

Flexible thoraxmade up ofmany segments

Cephalon(head)

Sclera acts as a tough skinbetween lenses.

Lens

Each large lens had its owncornea and was separatedfrom the lenses around itby sclera.

Cornea

299–251

Olenellus Paradoxides

Cross-section of aholochroal eye

Eye

Cornea is thetransparent coverof the lens.

26


EURYPTERIDS(SEA SCORPIONS)were the largest-ever arthropods.They belong to thechelicerates (“bitingclaws”), a group thatincludes scorpions and spiders.Sea scorpions appeared inOrdovician times and persistedinto the Permian. Among thelargest was Pterygotus, which livedmore than 400 million years ago andcould grow longer than a man. Beforepredatory fish evolved, sea scorpionswere among the most dominant huntersof shallow seas. Some species even crawledashore, where they breathed air by means ofspecial “lungs,” like those of certain land crabs.

HUNTERS AND SCAVENGERSMany species of sea scorpion were muchsmaller and less well-armed than Pterygotus.Eurypterus was only 4 in (10 cm) long andhad two short fangs. It would not have beenable to tackle the large prey that Pterygotuslived on. These creatures used their legs topull tiny animals toward their fangs, whichtore them up and fed them to the mouth.

Pterygotus swam bybeating its broadpaddles up and down.




BODY PLANLike all sea scorpions, Pterygotus had a two-part body. Its prosoma (front) bore the mouth, one pair of large eyes, one pair of small eyes, and six pairs of appendages. The long opisthosoma (rear) had 12plated tail segments called tergites. The first six tergites

contained pairs of gills and included the creature’ssex organs. Pterygotus’s telson, or tail, formed a

wide, short paddle. In some sea scorpions,the telson took the shape of pincers

or a spike.

SEA SCORPIONS

Walking leg

27

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Paleogene 65.5–23 Neogene 23–present


Large eye

Huge fangs (chelicerae)similar to a lobster’s claws

SEA SCORPIONS

METHOD OF ATTACKPterygotus had big, sharp eyes that could detectthe movement of small, armored fish on themuddy sea floor some way ahead. The huntercould have crawled or swum slowly toward its victim, then produced an attacking burst of speed by lashing its telson up and down.Before the fish could escape, it would begripped between the pincers of a great clawwith spiky inner edges. This fang would crushthe struggling fish and feed it to Pterygotus’smouth, which lay beneath its prosoma and between its walking legs.

PTERYGOTUS

Scientific name: PterygotusSize: Up to 7 ft 4 in (2.3 m) longDiet: FishHabitat: Shallow seasWhere found: Europe and North AmericaTime: Late SilurianRelated genera: Jaekelopterus, Slimonia

Small eye

28


HAWKLIKE HUNTERSMeganeura was a gigantic, primitive dragonfly with a 27-in (70-cm) wingspan. It flew to huntflying insects above tropical forests in LateCarboniferous times. Its features includedswiveling, multifaceted eyes like headlights, which were quick to spot movement and sharpenough to allow Meganeura to pounce on flyingprey. Meganeura flew by beating two pairs of wingsstiffened by “veins.” It dashed to and fro throughforests, changing speed and direction almostinstantly, grabbing insects with its legs, andbringing them up to its mouth to feed as it flew. Such giant protodragonflies had strongerlegs than living dragonflies, and could havetackled flying animals as large as cockroaches.



WINGS AS SHIELDSWater beetles almost identical tothis Pleistocene Hydrophilus fossilstill swim in ponds and streams. As in other beetles, their forewingsare hard, tough cases called elytra.These cover and protect the flimsyhindwings – the wings that theyuse to fly. To become airborne,they spread their hinged elytraand flap their hindwings. Beetlesdesigned along these lines dateback more than 250 million years to the Permian period.

Six jointed legs,as found inother insects.

Hydrophilus

Meganeura fossil


Fine veins stiffened and strengthenedthe wings.

Hard, shiny elytrapreserved in afossil beetle

THE FIRST KNOWN INSECTS were tiny, wingless arthropods that lived in theDevonian. Many scientists think that insects share an ancestor with thecrustaceans. By 320 million years ago, some insects had developedwings. Flying insects eventually evolved different types of wings.Flight helped insects find mates, escape enemies, and accessnew food supplies. The flowering plants that arose inCretaceous times provided food for nectar-lappingbutterflies and pollen-eating bees. By 150million years ago, antlike termites wereforming “cities” in which differentindividuals performed specialized tasks tohelp the colony thrive and to raise theiryoung. Later, ants, bees, and waspsalso formed colonies. Insectshave proven so successfulthat the world nowteems with millions of insect species. Noother land-basedarthropods are soplentiful or varied.

Antenna

EVOLVING INSECTS

29

299–251 Cretaceous 145.5–65.5 Paleogene 65.5–23 Neogene 23–present


EVOLVING INSECTS

FOREST FORAGERCockroaches such as Archimylacris

lived on the warm swamp forestfloors of North America and

Europe 300 million years ago,in Late Carboniferous times.Like living cockroaches,these ancient insects had alarge head shield with long,curved antennae, or feelers,and folded wings. Scuttlingaround the undergrowth,they chewed anythingremotely edible. Sometimesthey might have fallen prey to amphibians and very

early reptiles.

MEGANEURA

Scientific name: MeganeuraSize: Wingspan up to 27 in (70 cm)Diet: InsectsHabitat: Tropical swamp forestWhere found: EuropeTime: Late CarboniferousRelated genera: Meganeuropsis, Tupus

Wings fixed at right angles to the thorax

The wings of thisfossil cockroach,

Archimylacris, arewell-preserved.

Head with compoundeyes and bitingmouthparts

WINGS FROM GILLSThis Jurassic fossil insect was the nymph, or young, of Mesoleuctra – an ancientrelative of living stoneflies. Adult stoneflies have two pairs of wings that fold back against the body. Scientists believe thatinsect wings evolved from large gill plates on the legs, which helpedsuch insects breathe underwater.Stonefly ancestors may have raisedtheir gill plates like little sails, andused the wind to skim along the watersurface, as some stoneflies do today.

Meganeura

Long abdomen

Triassic 251–199.6 Jurassic 199.6–145.5

30


THE FLAT-SIDED, COILED SHELLS CALLED AMMONITES were named afterAmmon, an Egyptian god with coiled horns. Rocks that are rich in ammonite fossils also contain those of belemnites – long,tapering fossils that were named from the Greek word fordarts. Both groups were cephalopods – mollusks withsoft bodies, such as nautilus, octopus, and squid. Likesquid, ammonites and belemnites had tentaclesthat surrounded beaklike jaws. Both groups livedin the sea and moved by jet propulsion – theysquirted water one way to dart in the oppositedirection. Ammonites are among the mostplentiful fossils from the Mesozoic era, but neither they nor belemnites lastedbeyond the Age of Dinosaurs.

ECHIOCERASThe ammonite Echioceras lived and swam inshallow seas around the world in Jurassic times.Its narrow, loosely coiled shell was reinforced by the short, straight ribs that ran across it. In life, Echioceras’s tentacled head poked out of the shell’s open end as it foraged for food.Paleontologists believe that this ammonite was a slow-swimming scavenger, rather than anactive hunter. Like many ammonites, Echiocerasprobably wafted over the seabed and grabbedanything edible it could stuff in its beak.

INSIDE AN AMMONITEAmmonites lived in a shell that was divided into anumber of chambers. The innermost chamber was the oldest cavity. When the young ammonite outgrewthis home it built a bigger chamber next to it, which itmoved into. This process was repeated as the ammonitegrew. The old, empty chambers served as buoyancytanks. A tiny tube that ran through the chamberspumped out water and filled them with gas, which madethe ammonite light enough to float above the sea floor.

Ribs spacedwell apartstrengthenedthe shell.




AMMONITES AND BELEMNITES

Buoyancychamberinside shell

Tentacle

Section throughan ammonite

Tube

Beaklike jaws

Gill

StomachKidney

Heart

Ovary

Septum(dividing wall)

31

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Paleogene 65.5–23


BELEMNOTEUTHISBelemnites, such as Belemnoteuthis, resembledsquid. They were long-bodied creatures with

fairly large brains and big eyes. From the headend sprang 10 tentacles armed with suckers and

hooks. The muscular mantle – the front of thebody – had a winglike fin on either side. The

tapering rear end covered the back of theinternal shell. Belemnoteuthis used its hooked

arms to grapple small, slow-moving sea creaturesto its beak. To steer or swim slowly, Belemnoteuthis

flapped its fins. To dart forward or backward for a fast attack or a high speed getaway, it

propelled its body by squirting jets of water.Belemnoteuthis lived in a Late Jurassic sea that

once existed where Europe stands today.

AMMONITES AND BELEMNITES

INSIDE A BELEMNITEThis Cylindroteuthis fossil shows the main parts of abelemnite’s internal shell. The chambered phragmoconeprovided buoyancy for the middle of the body and helped to keep it level in the sea. The phragmocone’s tapering rearend slotted into the front of the long, narrow guard – a hardpart that often fossilized. One of the largest of all belemnites,Cylindroteuthis lived in deep offshore waters in Jurassic times.

ECHIOCERAS

Scientific name: EchiocerasSize: 2.5 in (6 cm) acrossDiet: Tiny organismsHabitat: Shallow seasWhere found: WorldwideTime: Early JurassicRelated genus: Asteroceras

Chamberedphragmocone in the body’sbroad front end

Mantle

Hookedtentacle

Loosely coiledshell with manyturns, known as whorls

Neogene 23–present

Head region

Long, pointedguard or pen

32


COTHURNOCYSTIS FOSSILResembling a strange, stalked flower turned to

stone, a Cothurnocystis fossil lies embedded in anancient piece of Scottish rock. Cothurnocystis belonged

to the carpoids – small, oddly flattened creatures thatlived on Early Palaeozoic seabeds. More than 400 million

years ago, this carpoid – small enough to fit in a human’shand – might have dragged itself across the seabed by its tail.

Scientist Richard Jefferies suggested that the tail enclosed anotochord, which might make the carpoids ancestral to fish.




Calcite platesprotecting the body

Calcite platesframing the head

Slits for expellingwater waste

TOWARD THE FIRST FISHMAJOR STEPS IN EVOLUTION before and early in theCambrian gave rise to early fish. First, millions of tiny cells clumped together to produce sponges. Then, different types of cells that carried out specialized tasks formed tissues in more advancedanimals, the eumetazoans. The firsteumetazoans had two layers of tissue.Later eumetazoans had threetissue layers. Further changes createdbilaterians – animalswith left and right sides, bodies made of many segments, and a front and rear with a mouth and anus. By 535 million years ago,small, long-bodied bilaterians called chordates had evolved a stiffening rod called a notochordthat foreshadowed an internal skeleton. Chordatesthat gained a brain, gills, muscle blocks, and fins became the world’s first fish.

Cothurnocystis

Inlet for foodand water

CALCICHORDATESCothurnocystis was a strange, boot-shaped animal ofa group that one scientist called calcichordates(“calcium chordates”), making it a chordate – anorganism that has a notochord at some point inits life. Its tail might have contained a notochord,and the small slits in its body might have filteredfood, just like the throat slits found in livinglancelets. However, most scientists believe it wassimply a weird echinoderm. Cothurnocystis had anouter “skin” of hard plates like a sea urchin – aliving echinoderm.

PUZZLING CONE TEETHConodont fossils puzzled paleontologists for more

than 150 years. They are tiny, toothlike fossils ofmysterious sea creatures that persisted for morethan 300 million years, yet seemed to leave noother trace. At last, in 1983, an entire fossilconodont animal was found. It was eel-like,with large eyes, and teeth inside its throat. Asconodont teeth appear to contain ingredientsof bone, some scientists consider conodonts

to be the world’s first vertebrates. However,conodonts formed a sidebranch of the

evolutionary line that led to fish.

COTHURNOCYSTIS

Scientific name: CothurnocystisSize: Cup diameter 2 in (5 cm)Diet: Edible particlesHabitat: Muddy sea floorWhere found: Western EuropeTime: OrdovicianRelated genus: Dendrocystites

33



TAIL CHORDATESLiving tunicates are close kin tothe ancestors of fish. Tadpoleliketunicate larvae possess notochords.They are called urochordates (“tail chordates”)because most of their notochord is in their long tails.Tunicate larvae swim around, then glue themselvesonto the seabed. Fish may have come from creaturessimilar to young tunicates that never settled down.

Tail, or stem, usedto drag the bodyover mud.

Notochord shrivelsas tunicate grows.

Conodont teethresembled the

teeth on a comb.

HEAD CHORDATESThe little eel-like cephalochordate (“head chordate”)called Branchiostoma (lancelet) living today is probably the best clue to the creatures that gave rise to fish.Branchiostoma and other cephalochordates do not have a head but a swelling of the notochord at the body’s front end that hints at the beginnings of a brain. In 1999,Chinese scientists described an earlier fossil creature thatthey believed would have had an anatomy very similar toBranchiostoma, but was more fishlike. They claim that 530-million-year-old Haikouella had a well-developed brain, eyes, a heart, and gill filaments. Suchcreatures might have been the world’sfirst craniates – creatures with a cranium or skull.

TOWARD THE FIRST FISH

Tunicate larva

Conodont elementson a pinhead

HeartMouthopening

V-shaped blocksof muscle

Living Branchiostoma

Eye Brain

Neural cord

Haikouella

34

VERTEBRATES CLADOGRAMVERTEBRATES HAVE AN INTERNAL SKELETON of bone or cartilage. The evolution of this skeleton allowed some vertebrates to supporttheir weight on land better than any other animal group. As a result,vertebrates have grown to sizes and taken to lifestyles that are beyondthe scope of most other animals. The most important group ofvertebrates are the gnathostomes – the jawed vertebrates. The mostsuccessful gnathostomes are the bony fish. Members of this groupinclude the ray-finned fish and the sarcopterygians – the lobe-finnedfish and four-footed vertebrates.


VERTEBRAL COLUMN AND BRAINCASE The vertebral column is achain of vertebrae that protectsthe spinal cord. Vertebrateshave distinct heads in whichthe brain and sensory organs are protectedby a skull.

JAWS The evolution of jaws allowedvertebrates to eat bigger items,develop diverse feeding styles,and push more water forrespiration through theexpanded mouth cavity.

BONY FIN SKELETON All bony fish have finbones. Muscles attached to these bones providebony fish with bettercontrol over their fins.Bony fish are the mostsuccessful gnathostomes.

MUSCULAR FIN BASESarcopterygians havemuscles at the base oftheir fins, as well as largeand powerful fin bones,which allowed some ofthem to clamber throughunderwater vegetation,and later to walk on land.

JAWLESS FISH

SPINY SHARKS

ARMORED FISH

RAY-FINNED FISH

COELACANTHS,LUNGFISH, AND

THEIR RELATIVES

CARTILAGINOUS FISH

Lamprey

Dunkleosteus andother armored fishwere among theearliest jawed fish.

Eusthenopteron fromthe Late Devonian

Jurassic Lepidotes fossil

Barracuda jaws

Vertebral columnand skull in asimple vertebrate

Bones in bony fish’s fin

Muscle Lobe-finnedfish’s fin

SARCOPTERYGIANSMuscular fin base

BONY FISHBony fin skeleton

GNATHOSTOMESJaws

VERTEBRATESVertebral column

and braincase

35

LIMBS WITH DISTINCT DIGITSSarcopterygians with distinctlimbs and digits are calledtetrapods. These vertebratesevolved in the Devonian fromaquatic or amphibious predatorsthat later adapted to life on land.

REDUCED PREMAXILLAEThe premaxillae are proportionallysmaller in the reptiliomorphs thanthey are in other tetrapods. Despitesharing this feature, the variousreptiliomorph groups may not be closely related.

AMNIOTIC MEMBRANEThe embryos of amniotes are protected by a watertightamniotic membrane. Theevolution of this membraneallowed amniotes to dispensewith the aquatic larval stagepresent in primitive tetrapods,and to colonise the land awayfrom bodies of water.

TEMNOSPONDYLS

LEPOSPONDYLS ANDLISSAMPHIBIANS

SEYMOURIAMORPHS

DIADECTOMORPHS SYNAPSIDS REPTILES

VERTEBRATE EVOLUTIONInvasion of the land is a minor part of the vertebratestory, for most of the group’s evolutionary history hasbeen played out in water. Primitive jawless fish werethe earliest vertebrates. They were superseded in theLate Paleozoic by jawed vertebrates. The evolution of muscular fins and well-differentiated limbs anddigits allowed lobe-finned fish to take to the land.Tetrapods evolved during the Devonian. By theCarboniferous, they had radiated into numerousaquatic, amphibious, and terrestrial groups.

Diadectes fromthe Early Permian

VERTEBRATES CLADOGRAM

Forelimb of Permiantemnospondyl Eryops

The premaxillae aretwo bones that formthe tip of the snout.

Skull ofreptiliomorphGephyrostegus

Chicken eggThe amniotic membranesurrounds the embryo.

In cladistic terms, birds are reptiles whoseforelimbs have becomewings, and who havefeathers instead of scales.

Domesticchicken

Mastodonsaurus fromthe Late Triassic

Digit

AMNIOTESAmniotic membrane

REPTILIOMORPHSReduced premaxillae

TETRAPODSLimbs with

distinct digits

36

FISH CLADOGRAMIN CLADISTIC TERMS, THE WORD “FISH” encompasses all vertebrates, as tetrapods – vertebrates that bear limbs with distinct digits – evolved frombony fish. Jawless fish evolved in the Cambrian from chordate animalsrelated to tunicates. In the Ordovician and Silurian, the gnathostomes, orjawed vertebrates, diversified into four groups – armoured fish, cartilaginousfish, spiny sharks, and bony fish. Cartilaginous fish and bony fish (includingtheir descendants tetrapods) survive today and, between them, dominate lifein water and on land.


CARTILAGINOUS SKELETONThe skeletons of cartilaginousfish are made of cartilage rather than bone. Many small,polygonal plates are embeddedin the cartilage surface – afeature unique to cartilaginousfish and present in the group’searliest members. These fish aresimple gnathostomes that maybe related to placoderms.

JAWSThe evolution of jaws wasthe key event in vertebrateevolution. It allowedvertebrates to eat biggeritems, develop diversefeeding styles, and pushmore water for respirationthrough the expandedmouth cavity.

HAGFISH

LAMPREYS

EXTINCT JAWLESSFISH

JAWLESS FISH ARMORED FISH

ELASMOBRANCHII(SHARKS AND RAYS)

SPINY SHARKS

HOLOCEPHALANS

(CHIMAERAS)

Devonian sharkCladoselache

Barracuda skulland jaws

VERTEBRAL COLUMNAND BRAINCASE The vertebral column is a chain of vertebrae thatprotects the spinal cord.Vertebrates have distinctheads in which the brainand sensory organs areprotected by a skull.

Lamprey

Dunkleosteus fromthe Late Devonian

Shark spinal column

Vertebral columnand skull in asimple vertebrate

CARTILAGINOUS FISHCartilaginous skeleton

GNATHOSTOMESJaws

VERTEBRATESVertebral column

and braincase

37

FISHY ORIGINSBoth jawless fish and the primitive jawed fish that evolved in the Ordovician were slow andinflexible compared to modern bony fish. Bony fish evolved bony bases and rays in their fins thatmade them swimmers with increased maneuverability.The evolution of the symmetrical tail fin in theCarboniferous allowed ray-finned fish to swim faster.Teleosts combined all of these features with jaws thatcould open especially wide, which increased theirability to draw water and prey into their mouths.

FISH CLADOGRAM

BONY FIN SKELETONAll bony fish have fin bones. Muscles attached to these provide bony fishwith better control over theirfins. Bony fish are the mostsuccessful gnathostomes.They include ray-finned fish, lobe-finned fish, and tetrapods.

FINS SUPPORTED BY RAYSRay-finned fish arose in theSilurian and have becomethe most diverse group ofaquatic gnathostome. Finrays give these fish finercontrol over the motion of their fins. Primitive ray-finned fish have distinctiverhomboidal scales covered by a hard outer layer.

SYMMETRICAL TAIL FINThe evolution of a spinalcolumn that did notextend as far into the tail fin as in earlier fishcreated the symmetricaltail fin. These tail finsproduce more thrust andallow faster swimming.

SUPRAMAXILLATeleosts and amiids areunited in the Halecostomi.Members of this Mesozoicand Cenozoic group have a supramaxilla, a new skullbone in the upper jaw thatformed part of a specialsystem for opening thejaws. The supramaxillaprovided the Halecostomiwith a wider gape.

SARCOPTERYGIANS

CHONDROSTEANS

(BICHIRS ANDSTURGEONS)

CHEIROLEPIDIDS PYCNODONTIFORMS

Cheirolepis fromthe Mid Devonian

Eusthenopteron fromthe Late Devonian

Pycnodus lived fromthe Mid Cretaceousto the Mid Eocene.

AMIIDS(BOWFINS)

Ray

Rudd

TELEOSTS

Supramaxilla

Bones in bony fish’s fin

Ray-finned fish’s fin

Sailfish tail skeleton

Skull and jawsof amiid

HALECOSTOMISupramaxilla

ADVANCED RAY-FINNED FISH

Symmetrical tail fin

RAY-FINNED FISHFins supported by rays

BONY FISHBony fin skeleton

38


JAWLESS FISHAGNATHANS (“WITHOUT JAWS”) WERE THE EARLIEST, most primitive fish.Their only living relatives are the hagfishes and lampreys – eel-shapedparasites that fasten onto other fish and feed on their flesh or blood.They were small in size – most less than 6 in (15 cm) long, though somegrew to 3 ft 3 in (1 m) – and many were tadpole shaped. They displayeda number of features that are considered to be primitive. Their mouthswere fixed open because they lacked jaws, they had no bony internalskeleton, and they lacked paired fins. Because they had fewer fins than more advanced fish, they were not very maneuverable inthe water. Early jawless fish lived in the seas, but theylater invaded riversand lakes. Theyswam by wagglingtheir tails, andsucked in foodparticles from the mudor water around them.Their bony armorprotected them from sea scorpions and other predators.




VERTEBRATE PIONEERSacabambaspis was a tadpole-shaped fish that lived 450million years ago. It swam bywaggling its tail, but had no other fins, which would have made braking and steering almostimpossible. Two tiny, headlightlike eyesgazed from the front of its armored head asit sucked in water and food scraps through theever-open hole of its mouth. Sacabambaspis lived inshallow seas, but its fossils have been found in the rocks of Bolivia’s high Andes. Old as they are, agnathans80 million years older are now known from China.

Backswepthorns helpedwith balance.

The long lower lobe of the tail gave the fish lift as it swam.

The back of the bodywas covered withflexible scales.

Large bony platesprotected thehead and chest.

Sensory organs, called alateral line, were present in the sides of the bodyand in the roof of the skull.

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BETTER BALANCECephalaspis was amember of theosteostracans, a largegroup of advanced jawless fish. Its key featuresincluded a big, bony head shield with eyes on top, amouth beneath, and sense organs on the sides and onthe top of the head. The upturned tail tended to tiltthe head down as it sucked in nourishment from mudon the floors of streams and ponds. Paired scaly flaps,similar to pectoral fins, provided lift and balance, anda dorsal fin helped stop the body rolling.

WING SHIELD

Scientific name: PteraspisSize: 8 in (20 cm) longDiet: Tiny water animalsHabitat: Shallow seasWhere found: Europe, Asia, North AmericaTime: Early DevonianRelated genera: Errivaspis, Protaspis

JAWLESS FISH

WING SHIELDPteraspis (“wingshield”) is so namedbecause it had

pointed, winglike,armored spines sticking

out from its sides. Itsheavily armored, pointed

head had a long, sharp snoutjutting out above and in front of

the mouth. Lacking jaws, the mouthwas fixed open and the animal might

have swum near the surface, guzzling tiny shrimplike creatures. Pteraspis and its

relatives were very successful during the LateSilurian and Early Devonian in terms of bothnumbers and diversity.

A tall, bony spine at the back of the head shieldserved as a dorsal fin.

Small eyes set in ahead shield made ofseveral bony plates

Long, pointed snout

Bony headshield witheyes on top

Body about 8 in (20 cm) long

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ARMORED FISHPLACODERMS (“PLATED SKINS”) WERE PRIMITIVE jawed fish. They are named for the broad, flat bony plates over the head and front of the body, whichprotected them from attack by larger placoderms and sea scorpions. Theyshared many anatomical features with sharks – backbones made of cartilage, for example – hinting that the two groups may have shared a common ancestor. Like sharks, placoderms probably had no swim bladder, and so had to keep swimming to avoid sinking. There were seven main groups ofplacoderms, including odd forms that were flattened like rays, forms with long, narrow, tapering bodies and tails, and forms with bone-plated “arms.”Some lived in the sea, some in fresh water, and they ranged in size from a few inches up to 26 ft (8 m) – the first fish to grow to such a large size.Placoderms were a very successful group. Although they lived almost entirely within a single geological period – the Devonian – they diversified to become the dominant vertebrates of the time.




FLAT OUTThe flat-bodied fish Gemuendina resembles a modern skate orray, but in fact it belonged to an ancient group of placodermscalled rhenanids. It had broad, winglike pectoral fins. A short,bony shield guarded its foreparts and tiny bony plates randown its slender tail. Much like living rays, Gemuendina swamwith rippling movements of its pectoral fins. Patrolling theseabed, it thrust out its jaws and crushed shellfish between its toothlike tubercules. Gemuendina lived in Early Devoniantimes where central Europe now stands, although similarprimitive placoderms occurred in North America.

Gemuendina fossil in fine-grained rock

Preserved headand trunk shields

FISH WITH “ARMS”Bothriolepis was among the strangest of placoderms. Up to 3 ft (1 m) in length, it possessed jointed “arms” made of bony tubes that enclosed its long,narrow pectoral fins. Bothriolepis might have used these arms to dig for food in the mud of the seabed. Alternatively, the arms could have pulled the fish over dry land as it migrated from one pool to another, breathing air with its “lungs.” Fossils of this placoderm are found in marine and freshwaterdeposits worldwide. Scientists suspect that it lived in shallow Devonian seas, swimming upstream to spawn, just as salmon do today.

Rock slab containing manyfossils of Bothriolepis

Each jointed “arm” wasa fin inside a bony tube.

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ARMORED FISH

HEAD ARMORDunkleosteus was a member of a group of Late Devonianplacoderms called arthrodires or “jointed necks.” It rocked backits head to open its jaws, revealingrazorlike, self-sharpening bonyplates that served as teeth. Its victims probably includedsmall, early sharks.

Bony tooth plates with sharp, cutting cusps

Unprotectedscaleless tail

Dorsal fin

Head and chestshields connectedby a ball-and-socket joint

BONY ONEOne of the largest and most

formidable of all placodermswas Dunkleosteus, named after

American paleontologist D.H. Dunkle.With massive head and jaws, it reached a

size of around 16 ft (5 m). Only its head andshoulder areas were covered by a protective

shield, leaving the big, fleshy pectoral finsfree to help it maneuver. The rest of the bodyhad no armor or scales. Scientists are unsureabout the shape and habits of Dunkleosteus. It

may have been sharklike, swimming andhunting actively, or it may have had an

eel-shaped body fringed with long,ribbon-like fins and lived on the

sea bed, swimming sinuously.

DUNKLE’S BONY ONE

Scientific name: DunkleosteusSize: 16 ft (5 m) or more longDiet: FishHabitat: OceansWhere found: Europe, Africa, North AmericaTime: Late DevonianRelated genera: Bruntonichthys, Bullerichthys

Huge head and chestshield of Dunkleosteus

Devonian 416–359.2 Carboniferous 359.2–299 Permian Cambrian 542–488.3 Ordovician 488.3–443.7 Silurian 443.7–416


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DEVONIAN PREDATORSea levels were high in the Devonian, and warmtropical waters teemed with invertebrate life,including corals, echinoderms, trilobites, andsponges. So many new forms of fish evolved duringthis period that it is sometimes called “the age offish.” Primitive sharks, lobe-finned fish, and lungfishdiversified, as did the ray-finned fish and placoderms(“plated skins”). At more than 16 ft (5 m) in length,Dunkleosteus was one of the largest of the predatoryplacoderms, feeding on sharks and other fish.



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ARMORED FISH

44


SHARKS AND RAYS




SHARKS ARE SUPERB SWIMMING and killing machines and have been among the top ocean predators for more than 400 million years. Their basic features – astreamlined shape and jaws bristling with razor-sharp fangs – have changed little

in this time, although many different kinds ofsharklike fish have evolved. These include rat fish with big eyes and ratlike tails, and skatesand rays with wide, flattened bodies andbroad, low teeth. Sharks and their relativesare known as Chondrichthyes (“cartilage

fish”) because their skeletons are made of cartilage rather than bone. Other

features typical of the group includeteeth and scales that are continually

shed and replaced, no gill covers,and paired fins. Sharks also lack

swim bladders, which means they must keep swimming

to avoid sinking.

Snout shorter andblunter thanmodern sharks

Large pectoral fins

Streamlined, torpedo-shaped body

CLADOSELACHE

Scientific name: CladoselacheSize: Up to 6 ft 6 in (2 m) longDiet: Fish and crustaceansHabitat: SeasWhere found: North AmericaTime: Late DevonianRelated genus: Monocladodus

Rows of teeth grewforward to replace oldones that fell out.

Short main dorsal fin

CLADOSELACHECladoselache is one of the earliest known sharks. Its well-preserved fossils have been found in LateDevonian rocks that date back 400 million years. This formidable carnivore hunted fish, squid, and crustaceans thatlived in a sea that existed where Ohio now stands. In some waysCladoselache resembled today’s sharks, with a torpedo-shaped body,big eyes, large pectoral fins, and large tail, but in other ways it was very different from modern species. Its snout was shorter andmore blunt, its mouth was located at the front of the head ratherthan underneath, and its upper jaw attached to the braincase at the front and back, not just at the back. This meant that the mouth could not open very wide.

45



SHARKS AND RAYS

Sharp tooth of theshark Carcharocles

WIDESPREAD PREDATORSHybodus was a blunt-headed shark with prominent fin spinesand distinctively shaped scales. Growing up to 8 ft (2.5 m) inlength, it closely resembled modern sharks although its jawswere of different design, carrying two different types of teeth.Pointed teeth at the front were used to seize its prey of fish,while blunt teeth at the back were used to crush bones andshells. Males had curious barbed hooks on the sides of their

heads, attached to the braincase. The genus Hybodusflourished for much of the Mesozoic Era, and fossils

of different species have been found as far apart as North America, Europe, Asia, and Africa.

SUN RAYThe stingray Heliobatis (“Sun ray”) was a flat-bodied,freshwater fish that lived in North America about 50million years ago. Up to 12 in (30 cm) in length, its flat,round body had a long whip-like tail armed with barbedspines. Heliobatis lay on the bottom of rivers and lakes,snapping up crayfish and shrimp. When attacked, it lashed out with itstail. The spines at thetip could perhapsinject a powerfulpoison through theskin of its enemy.

SPINY CHESTAmong the strangest of all prehistoric creatures wasStethacanthus (“spiny chest”), a small shark that lived about360 million years ago. The male carried a bizarre tower onits back, the broad, flat top of which was covered by a brushof spines. Another spiny patch grew on top of its head. Thefunction of the spiny patches is uncertain. Viewed head on,they may have resembled a pair of huge jaws, thus scaringoff predators, or they may have been important in mating.

Large pectoral finshelped the shark tomaneuver

Long upper taillobe similar to thatof modern sharks

Barbed spines on the head show that this was a male Hybodus.

The fin rays radiated like the rays of the Sun.

Spine-covered “tower”

SHARP OR BLUNT Prehistoric sharks and rays are often identified from their hard, durable teeth because their gristlyskeletons did not readily fossilize. The sharp, serratedtooth shown here belongs to the huge Eocene sharkCarcharocles, which killed and ate large sea mammals.It is very different from the broad flat toothplate ofthe ray Myliobatis, which was designed to crunch upthe hard shells of armored creatures, such as as crabs and clams.

Flat toothplate of the ray Myliobatis

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SPINY SHARKSACANTHODIANS OR “SPINY SHARKS” MAY HAVE predated placoderms as the first fish with jaws. They were named for their streamlined, sharklike bodieswith upturned tails, and for the thorn-sharp spines that formed the leadingedges of their fins. Most spiny sharks had deep, blunt heads, big mouths,and at least two dorsal fins. Although their cartilage backbone reminds usof a shark’s, acanthodians had a braincase, gills, and other features morelike those of bony fish that dominate the waters of the world today. Theoldest known acanthodian fossils come from Early Silurian rocks in China.Evolving in the sea, acanthodians invaded lakes and rivers eventually. Most were small – the largest 6 ft 6 in (2 m) long. The group persisted for maybe 170 million years – as long as the dinosaurs – with a heyday in the Devonian.

Large eyes suggest thatClimatius hunted by sight not scent




INCLINED FISHClimatius (“inclined fish”) was named for its upward tilted tail. This small river fish was a member of theClimatiiformes, the earliest group of acanthodians.It had big eyes and sharp teeth suggesting that itwas an active predator. It is likely that Climatiuszoomed low over the beds of seas or rivers in searchof prey – tiny fish and crustaceans. Its defensivefeatures included heavy, bony shoulder armor,spiny fins, and four pairs of extra finlike spines that protected its belly. These helped makeClimatius difficult for larger predators to tackle. Distinctive ridges on

surface of Gyracanthusfin spine

SPINY PROTECTIONFin spines up to 16 in (40 cm) long are the best known remainsof the spiny shark Gyracanthus. Fossils of this well-defendedanimal are found in Carboniferous rocks of North America

and Europe. The group to which Gyracanthus belongsprobably evolved in Antarctica but spread around

the world. Some of these acanthodians carriedpectoral fin spines that were half their

body length as protectionagainst large, fierce

predators.

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SPINY SHARKS

RIGID FINS The shoulder girdles of spinysharks such as Climatius beganas two separate bony platesconnected to the spinypectoral fins on each side ofthe body. Later they evolvedinto plates connected by anarrow plate that ran acrossthe chest. Other plates wereadded later, until they formeda rigid structure that lockedthe pectoral fins in position.The fixed fins served ashydroplanes, providing lift as Climatius swam forward.

Non-retractable spines added to drag as the fish swam.

Caudal (tail) fin was present onlybelow the upturned tail lobe.

Thick spines on theback and belly madeClimatius hard toswallow.

INCLINED FISH

Scientific name: ClimatiusSize: 3 in (7.5 cm) longDiet: Small fish and crustaceansHabitat: RiversWhere found: Europe, North AmericaTime: Late Silurian to Early DevonianRelated genus: Brachyacanthus

Pectoral finslocked in position

Pectoral finsconnected to bony plates

HAND SPINECheiracanthus (“hand spine”) was a deep-bodied acanthodian about 12 in (30 cm) in length. It had a blunt head,upturned tail, and fins protected by spines.Unlike many other acanthodians, it had just a solitary dorsal fin. Cheiracanthus swam at mid-depth in lakes and rivers, seizing small prey in itsgaping jaws. Whole fossils of this fish occur only in Mid-Devonian rocks in Scotland, but its distinctive small, ornamented scales crop up around the world, as far south as Antarctica.

Cheiracanthus fossil in Old Red Sandstone rock

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EARLY RAY-FINNED FISHBONY FISH ARE THE MOST NUMEROUS and diverse of all livingvertebrates, and more than 20,000 of them belong to one giant group – the actinopterygians or “ray fins.” They arenamed for the straight bony rays – controlled by muscles in the body wall – that jut out from the body and stiffen the fins.The earliest known ray fins lived 410 million years ago. Thefirst group to evolve were the paleoniscoids (“old, codlikefish”), which were small with thick scales, inflexible stiff fins,long jaws, and long upper tail lobes. By moving air into andout of special “lungs,” they could control their level in thewater, even though they lacked swim bladders. A few differentkinds of paleoniscoids evolved during the Devonian Period but more than 36 family groups appeared later, in theCarboniferous and Permian. After that, new kinds of bony fishcalled neopterygians (“new fins”) began to take their place.

HAND FINCheirolepis (“hand fin”) was one of the earliest ray-finned fish.Only parts of its backbone were actually made of bone – therest was made of gristle and so was not often preserved infossils. Unlike modern bony fish, Cheirolepis had pectoral fins (the equivalents of arms) that grew from fleshy lobesprojecting from its body. It was covered in smalloverlapping scales thickly coated with a specialenamel known as ganoin. This fish was aneager hunter, swimming fast to catch prey in freshwater pools and streams. It couldopen its jaws very wide to swallowanimals two-thirds of its own length. As Cheirolepis swam, its tall dorsal fin and the large anal fin below its body helped to stop it rocking in the water.

LIVING FOSSILSAbout a dozen species of bichirs still livein freshwater habitats in Africa, where theyfeed on small creatures such as worms andinsects. These long-bodied, ray-finned fishcan be traced back to ancestors that lived400 million years ago. Their skeletons arelargely made of cartilage, they have big,enamel-covered scales, and their pectoralfins sprout from fleshy lobes.

Relatively large eyes




REDFIELDIUS About 8 in (20 cm) in length, Redfieldius swam in lakes and streams about 210 million years ago. Its group, theredfieldiids, are thought to have evolved in Australia or South Africa and then spread to North Africa and North America in Early Mesozoic times, when all these lands were joined. The skull and fins of Redfieldius are more advanced in design than those of the first ray-finned fish.

Long jaws equippedwith many tiny teeth

Pectoral fins on fleshy lobes

HAND FIN

Scientific name: CheirolepisSize: 10 in (25 cm) longDiet: Small invertebratesHabitat: Fresh waterWhere found: Europe, North AmericaTime: Middle to Late DevonianRelated genera: Moythomasia, Orvikuina

49



EARLY RAY-FINNED FISH

LEPISOSTEUSThis streamlined freshwater predator, about 28 in (70 cm) long, had dorsal and anal fins placed so farback on its body that they almost touched its tail.Despite its “old-fashioned” enameled scales, it is more advanced than the first ray-finned fish. About 50 million years ago, Lepisosteus would have lurked inshallow weedy waters of what is now Wyoming. It probably lay in wait for its prey of small fish, seizing them in sudden bursts of speed between its long, narrow, toothy jaws. Livingmembers of its genus include the gars of North America.

STURGEONBest known for producing eggs that people eat ascaviar, sturgeons are living “prehistoric” ray-finnedfish. The two dozen kinds alive today live in northernseas and swim up rivers to spawn. Several of thesespecies are endangered by over-harvesting, damconstruction, and pollution. They feed on smallanimals and plants, which they suck into theirtoothless mouths. The largest can grow to lengths of 10 ft (3 m) and weigh up to half a ton (0.5 tonnes).Like bichirs, they have cartilage skeletons, and likeCheirolepis they possess uptilted tails and “old-fashioned” scales and fin rays.

Tall dorsal fin tended topush the head down whenswimming. Paired finsbelow the body helped to keep the head up.

Characteristic upturned tail

Body flexed powerfullywhen swimming

Lepisosteus fossil from the Eocene

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PRIMITIVE TELEOSTNo longer than a human hand,Leptolepides was a primitive bony fish that lived about 150 million years ago. It swamin shoals in tropical lagoonswhere Germany now stands.Like carp and other modernteleosts, it was able to protrudeits mouth to take in its food –plankton in the surface waters.Its bony scales were strong butthin, flexible, and light,making it an agile swimmer,and its tail’s supporting raysshowed other signs ofprogressive change.




Leptolepides, a smallLate Jurassic teleostfrom Europe

IMPROVED TYPES OF RAY-FINNED FISH called neopterygians (“new fins”)began to appear in Mesozoic times – the Age of the Dinosaurs. Thesenew forms had shorter jaws than before, but their mouths could openwider, and tooth plates in their mouths formed bones for grinding upfood. Changes in the design of the fins and tail, which became moresymmetrical, made neopterygians faster and more agile in the water.However, the biggest changes at this time occurred in the group ofneopterygians known as teleosts (“complete bones”). These evolveddefensive fin spines, deep but short bodies, and immensely powerfultails to drive them along. Swim bladders – air-filled sacs – helpedcontrol their buoyancy, and they could protrude their mouths to seizeor suck in food. Spiny teleosts also had lighter, thinner scales thanearly ray-finned fishes. There are more than 20,000 teleosts living today, demonstrating the success of the design.

SCURFY SCALESLepidotes (“covered in scurfy scales”) was a bony fishnearly as long as a human. In many ways it lookedvery different from the first ray-finned fish. It wasfar bigger, with a deeper body, a swim bladderfor controlling buoyancy, shortened jaws,and a wider gape. Like early ray-finnedfish, its body had a coat of thicklyenameled scales that resembled rows of shiny tiles. Lepidotes cruisedabove the floors of lakes, lagoons,and shallow coastal waters, crunchingshellfish with its strong teeth. Despiteits size and protective scales, Lepidotes itselfwas sometimes snatched and gobbled up by big fish-eating dinosaurs: the spinosaurs.

Heavily enameledoverlapping scales madethe body inflexible.

SCURFY SCALES

Scientific name: LepidotesSize: Up to 5 ft 6 in (1.7 m) longDiet: Shellfish Habitat: Lakes and shallow seasWhere found: WorldwideTime: Triassic–CretaceousRelated genera: Acentrophorus, Corunegenys

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Short, deep bodyresembles that of aliving cichlid, the Acara.

Relatively deep body

SWORD RAYXiphactinus was a primitive teleost that swam in Late Cretaceous seaswhere North America, Europe, and Australia now stand. At up to 14 ft(4.2 m) in length it was as large as today’s largest bony fish. Swinging itsshort “bulldog” jaws open wide to reveal its prominent conical teeth, itcould seize and then swallow a fish as long as a human. This is knownbecause the guts of one fossil Xiphactinus contain the remains of Gillicus,another neopterygian, which was 6 ft (1.8 m) long. It is thought that some

Xiphactinus died because theytried to swallowprey that was too big.

Number of fin rays ofanal fin is the same asthe number of theirsupport bones – afeature of neopterygians.

Top and bottom taillobes of equal length

OLD ACARA Priscacara was a spiny-rayed perchlike teleost that grew to about 6 in (15 cm) in length. It lived in NorthAmerica about 45 million years ago and was an ancestorof damselfish, small fish found today on coral reefs inwarm oceans. Stiff spines protected its dorsal and analfins, and its short jaws were crammed with tiny teethallowing it to snap up snails and small crustaceans in lakes and streams.

Large lower jaw

PANDER’S FISH

Scientific name: PanderichthysSize: 3 ft 3 in (1 m) longDiet: Fish and crustaceansHabitat: Shallow poolsWhere found: EuropeTime: Late DevonianRelated genera: Elpistostege, Obruchevichthys

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LOBE-FINNED FISHTHE BONY FISH THAT SWAM IN SEAS and freshwaters 400million years ago belonged to two large groups – lobefins and ray fins. Lobe-finned fish, or sarcopterygians,were so called because their fins sprouted from fleshy,muscular lobes reinforced by bone. Many also possessed a type of lung in addition to gills and so could breathe inair and in water. A variety of lobe fins arose during theDevonian period, among them lungfish, coelacanths(“hollow spines”), and Osteolepis (“bone scale”). From thedescendants of Osteolepis or its kin came air-breathing lobefins that would take an important place in evolutionaryhistory. As some of their fins shrank, others evolved intolimbs and they became the ancestors of all land-livingvertebrates. By Late Palaeozoic times, lobe-finned fishthrived in seas and rivers worldwide. Today only onecoelacanth species and six kinds of lungfish survive.

HORN TEETHCeratodus (“horn teeth”) was a freshwater lungfish that lived worldwide throughout the Age of Dinosaurs.Tapered at both ends, it grew to a length of 20 in (50 cm). It had two pairs of leaf-shaped, fleshy fins,together with a long, pointed fin formed by the tail finand two others that had met and joined. The crinklytoothplates anchored to its jaws allowed it to crunchup its food of fish, frogs, and snails. It had gills, butcould also breathe through its nostrils at the watersurface, using its swim bladder as a kind of lung.




PANDER’S FISHIn the 1990s, scientists made an important discovery about the LateDevonian lobe fin Panderichthys. Their studies revealed that thisfreshwater sarcopterygian was one of the closest known ancestorsof four-limbed vertebrates – closer even than Eusthenopteron. Ithad a long, narrow body and a long, large, flat head witheyes on top. Its nostrils were low on its snout, and itsteeth were covered with enamel folded the same wayas in some early four-legged animals. The way itsribs joined its backbone, and the shape of itsskull bones also made it more like a tetrapodthan a fish.

Broad, flat head ofPanderichthys, witheyes located on topand undershot mouth, openingbelow the snout

Ridged upper andlower toothplates of Ceratodus

GOOD STRONG FINEusthenopteron (“good strong fin”) was a long-bodied, predatoryfreshwater fish with a three-pronged tail. Nostrils opened intoits mouth, and details of its skull, teeth, backbone, and thebones of its paired pectoral and pelvic fins were similar to those of the first four-legged animals. It lived in Late Devonian North America and Europe. Scientists once thought that itcould haul itself over land from pond to pond on its stubbyfins, breathing air through a lunglike swim bladder. However,closer examination of its fins suggests thatthey may not have workedwell as limbs.

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LOBE-FINNED FISH

LIVING COELACANTH Latimeria, a coelacanth 5 ft (1.5 m) long, shares features with ancestors that lived

350 million years ago. Fleshy lobes supportsome of its fins and enameled scales protectits body. Its “frayed” tail is a reminder of thename crossopterygian (“fringe fin”), which issometimes used for the coelacanth group.People thought all coelacanths were extinctuntil one was caught off South Africa in 1938.

Powerful fins, which could pushEusthenopteronthrough shallow waters

Eusthenopteronfossil

Large muscularpectoral finssupported by “arm” bones

Narrow, fleshy,fin-fringed tail

No dorsal or anal fins

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55

Amphibians and ReptilesAbout 360 million years ago, a fish with lungs

crawled ashore on stubby fins that had evolved

as limbs. So vertebrates set off upon their great

adventure on dry land. This section begins with

the early tetrapods – four-footed amphibious

creatures. From weak-legged, crocodile-sized

“newts” to sturdy landlubbers, all these creatures

laid small unprotected eggs in water. Eventually

small lizardlike tetrapods began to produce eggs

that were protected by a shell. So arose the reptiles

– animals whose waterproofed, well-nourished eggs

enabled them to breed on land. Fossils and lifelike

models reveal the incredible variety of prehistoric

reptiles that once ruled land, sea, and air.

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EARLY TETRAPODS ANDAMPHIBIANS CLADOGRAMTETRAPODS, THE LIMB-BEARING VERTEBRATES, evolved in the Devonian from lobe-finned fish. The earliest tetrapods were much like their fish ancestors and were probably lake-dwellers that only occasionallydragged themselves onto land. More advanced tetrapods were bettersuited for life on land. They had stronger limbs, each with only fivedigits. All later tetrapods – which include the extinct temnospondyls, the lissamphibians, and the amniotes – inherited this five-fingered limbplan. As tetrapods evolved, some of the skull bones seen in their fishancestors became lost or reduced in size. The tetrapods best suited for life on land – the amniotes and diadectomorphs – evolved a strengthened junction between their hips and vertebrae.

AMPHIBIANS AND REPTILES

VENTASTEGA

LIMBS WITH DISTINCT DIGITSWell-formed limbs anddigits unite the tetrapods.Another feature – a “starburst”pattern on the skull – hasallowed poorly fossilizedmembers to be identified.

ACANTHOSTEGA

VERTEBRAL PEGSInterlocking pegs calledzygapophyses project from the ends of vertebrae.Zygapophyses help stiffenthe spine, and allowed earlytetrapods to carry theirbodies off the ground.

ICHTHYOSTEGA

BAPHETIDS

OLECRANONPROCESSA bony region onthe lower arm calledthe olecranon process unites tetrapods higher than Acanthostega. The olecranonprovided leverage for powerful arm muscles.

FIVE-DIGIT HANDThe presence of fivedigits on the hand unitesbaphetids, temnospondyls,lissamphibians, and highertetrapods. Five may be the bestnumber of digits for tetrapods thatuse their limbs for walking insteadof paddling.

Ventastega’s body and tailwere fish-like, and its limbswere used as paddles.

Like other primitivetetrapods, Acanthostegawas a large predator thatlurked among waterplants.

Ichthyostega’slimbs were madefor paddlingthrough water andshuffling on land.

Eryopsforelimb

Digit

Eucritta from theCarboniferous

Olecranonprocess

Ichthyostegaforelimb

Humanvertebrae

Frontzygapophysis

Rearzygapophysis

Ventastegaforelimb

Digit

Limbs with distinct digits

Interlockingvertebral pegs

Five digits or less on hand

Olecranonprocess

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TEMNOSPONDYLS

ABSENT INTERNASAL BONESTemnospondyls and highertetrapods are united by theabsence of the internasal bones. The factors that causedthese bones to be lost remainunknown. It may be that theycreated zones of weakness along the midline of the snout.

REDUCED PREMAXILLAEThe premaxillae are proportionallysmaller in reptiliomorphs than they are in other tetrapods. Despitesharing this feature, the variousreptiliomorph groups may not be closely related.

TWO-VERTEBRAE SACRUM The sacrum of diadectomorphsand amniotes consists of twovertebrae, rather than one. This reinforced sacrum wouldhave allowed these creatures tobecome larger, heavier animals.

Proterogyrinus fromthe Carboniferous

LISSAMPHIBIANSSEYMOURIAMORPHS

DIADECTOMORPHS AMNIOTES

Lizard

ANTHRACOSAURS

TETRAPOD EVOLUTIONPrimitive tetrapods with multiple fingers and toes appearto have been largely restricted to watery environments.The fossil record shows that after tetrapods with five-fingered hands evolved early in the Carboniferous, they diversified rapidly and gave rise to most of the major groups within less than 30 million years. Alltetrapods that are not amniotes were formerly calledamphibians. However, many fossil animals that have beencalled amphibians were not in fact related to each other.The word amphibian is often not used as a formal term.

EARLY TETRAPODS AND AMPHIBIANS CLADOGRAM

The premaxillae aretwo bones that formthe tip of the snout.

Frog

Mastodonsaurus fromthe Late Triassic

Skull of reptiliomorphGephyrostegus

Tetrapodskulls

Internasalbones

Internasals missingfrom skull of moreadvanced tetrapod.

Lizard pelvic girdleand sacral vertebrae

Two sacralvertebrae

Absent internasalbones

Reduced premaxillae

Sacrum with two vertebrae

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THE TETRAPODS, MEANING “FOUR FEET,”are the group that includes all livingvertebrates with four limbs anddistinct digits, or animals whoseancestors conformed to this standardpattern. Experts once thought that limbsevolved so that early tetrapods could crawl ashore,but new finds cast doubt on this idea. Early tetrapods, such as the Devonian Acanthostega, evolved from lobe-finnedfish, and were still tied to life in water. They had paddlelike limbs,gills, and tail fins. However, they also possessed many of the featuresinherited by all later types, including distinct digits (often more thanthe usual five), limbs with wrist and elbow joints, and vertebrae withinterlocking pegs. Because the earliest tetrapods were apparentlyaquatic predators, it seems that these features all evolved in the water.

EVOLUTION OF DIGITSDigits – fingers and toes – evolvedfrom the fin bones of lobe-finnedfish like Eusthenopteron. The earliest digit-bearing vertebrateswere long thought to have fivedigits – the pattern founduniversally in later forms.However, we now know thatIchthyostega, Acanthostega, and

possibly other tetrapods possessedseveral more fingers and toes, challenging

the old idea that possession of five digits is afeature inherited by tetrapods from the very firstfour-footed vertebrates. Advanced tetrapods maypossess five digits simply because this is the bestnumber when the limbs are used for walking,rather than as paddles.

TETRAPOD ORIGINSAmong the earliest tetrapods areElginerpeton from Devonian Scotland,Metaxygnathus and Ventastega. These animals are included in thegroup because of distinctive skull features, even though scientistsdo not know if they had limbs and digits. This reconstruction ofElginerpeton assumes that it looked similar to Acanthostega. The very first tetrapods, which include Obruchevichthys from Latvia andMetaxygnathus from Australia, are from the late Devonian (about365 million years ago). Footprints found in Australia show thatfour-footed animals were walking on land even at this time.

Paddlelike tail sweptfrom side to sidewhile swimming.

Fish fins lackboth a wrist regionand distinct digits.

Numerous small bonesform the fin skeletonsof lobe-finned fish.

Bony rays supported the fins that grew from the top andbottom of the tail.




ACANTHOSTEGA

Scientific name: AcanthostegaSize: 3 ft 3 in (1 m) longDiet: Insects, fish, smaller stegocephaliansHabitat: Lakes and pondsWhere found: GreenlandTime: Late DevonianRelated genera: Ichthyostega, Tulerpeton

Ichthyostega fin/hand

EARLY TETRAPODS

Hindlimbs weredirected sideways and backward,functioning best as a paddle.

Artist’s restoration of Elginerpeton

Early tetrapods werelarge – between 20 in(50 cm) and 40 in (1 m) long.

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ACANTHOSTEGATetrapods like Ichthyostega and Acanthostega from Late Devonian Greenland had many fishlike features, including a tail fin, gill bones, and paddlelike hindlimbs. They appear to have been aquatic predators.Intriguingly, these animals had multiple digits – Acanthostega had eight fingers and Ichthyostega had seven toes. These features suggest that the

evolution of limbs and digits first occurred in the water, and noton land. Acanthostega and its relatives might have ventured

onto land occasionally (Ichthyostegahad broad ribs that could havesupported it out of water), but their limbs were poorly

adapted for walking.

FISHLIKE SKULLThe skull of Acanthostega was streamlined in shapeand well suited for grabbing fish and other aquaticprey. This well preserved skull is similar to that of the lobe-finned fishes, ancestors of the earliest

limbed vertebrates. The downturned tip of thesnout is due to distortion during fossilization. Like

fishes, early limbed vertebrates still had a system ofsensitive canals, called lateral lines, on their skull bones.

CHANGING INTERPRETATIONSOld reconstructions show Ichthyostega on all fours. Theargument was that limbs and digits had evolved after fishtook to crawling on land – perhaps in search of prey or

new ponds. However, we now know that limbsand digits probably evolved in

aquatic animals, possibly tohelp their owners clamberthrough aquatic plants. Four-footed postures for theseanimals are unlikely as thehindlimbs were so flipperlike.

Interlocking pegs, calledzygapophyses, on thevertebrae helped stiffenAcanthostega’s spine

All early limbed vertebrates have adistinctive patterned skull surface.

Unlike fish,Acanthostega had a distinct bony wrist region.

EARLY TETRAPODS

Only three bones, the humerus, radius,and ulna, form thearm skeleton.

Acanthostega skull

The eight fingerswere probablywebbed together to form a paddle.

Large eyesdirected upwardand sideways.

Old model ofIchthyostega

The teeth were slim,sharply pointed, andconical.

Acanthostegaprobably caughtother vertebratesas prey.

Ordovician 488.3–443.7Cambrian 542–488.3 Permian Carboniferous 359.2–299Devonian 416–359.2Silurian 443.7–416

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TEMNOSPONDYLSTEMNOSPONDYLS WERE A LARGE AND DIVERSE group of aquatic,amphibious, and terrestrial animals. Their fossils are knownfrom Paleozoic and Mesozoic rocks worldwide. Most earlytemnospondyls were aquatic, salamander-like predators, but some, such as Dendrerpeton, were land-livingpredators with stout limbs, short bodies, and eyes on the sides of their heads. Unlike modernsalamanders and frogs, however, temnosponylsdid not have smooth naked skin – instead,their bodies were scaly. Some later landtemnospondyls had armor on their backsor over their whole bodies. Other advancedtemnospondyls stayed in the water andbecame gigantic predators. Some of thesehad long skulls and resembled moderncrocodiles. They were not necessarilyrestricted to freshwater, and some appear to have been sea-dwellers. Fossils show that they went through a larval stage.

METOPOSAURSDistantly related to Mastodonsaurus, metoposaurs

were a group of large, mostly aquatic temnospondyls. Allmetoposaurs, including this Buettneria from Late Triassic NorthAmerica, had large flattened skulls. This fossil was missing theend of its tail, and the restorers extended it, based on the ideathat Buettneria was a long-tailed swimming predator. However,recent investigations suggest that Buettneria had a short tail andprobably laid in wait on the riverbed, grabbing prey as they camewithin range. An African metoposaur called Dutuitosaurus didhave a tail more like the one shown here, suggesting that itactively swam after fishes and other prey.

MASS DEATHSSome kinds of temnospondyls are preserved in mass deathfossils. Hundreds of individuals seem to have perished and been buried together. The fossil below records a mass death ofTrimerorhachis, a Permian temnospondyl from North America. Theformation of these mass death assemblages is still controversial.Traditionally it was thought they were created when the poolsthese animals lived in dried up during a drought. Some expertsnow suggest that they formed from the gradual collectingtogether of bones by water currents. Another idea is that thesetemnospondyls died together in sudden mudflows or floods.



Trimerorhachis mass death fossil

Mastodonsaurusprobably spent nearly allof its time in the water.

Nearly allmetoposaurs had awide, flattened body.

Reconstructed Buettneria skeleton

Small, weak limbs suggest that metoposaurs did not walk on land much.

299–251

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CRETACEOUS SURVIVORSTemnospondyls were once thought to have been extinct by the end of theTriassic, but recent discoveries show that they survived as late as the EarlyCretaceous. Siderops from Jurassic Australia had a huge broad head andbladelike teeth. It probably ate aquatic animals, but also appears to havebeen well-equipped to grab land animals, like small dinosaurs, from thewater’s edge. All Jurassic and Cretaceous temnospondyls belonged to a group called the brachyopoids. Why these survived while all othertemnospondyls died out is unknown. Perhaps they lived in places thatwere less affected by environmental changes that wiped out their relatives.

TEMNOSPONDYLS

MASTODON LIZARD

Scientific name: MastodonsaurusSize: 7 ft (2 m) longDiet: Other temnospondyls, fishHabitat: Lakes, ponds, and swampsWhere found: Europe and North AfricaTime: TriassicRelated genera: Heptasaurus, Eryosuchus

Mastodonsaurus couldprobably hide underwater withjust its eyes above the surface.

Sensory grooves on its skullallowed Mastodonsaurus todetect vibrations made in the water by its prey.

Tusks could havebeen used to holdlarge prey animals.

Sideropsgrew to about8 ft (2.5 m) inlength.

Skull twice as broad asthe body.

Notches at the back of the skullcaptured vibrations, allowingMastodonsaurus to hear.

Numerous small sharpteeth lined both upperand lower jaws.

The tail was short butmay have served as a paddle whenswimming.

Skull up to 4.5 ft (1.4 m)long in the biggestindividuals.

Huge curvedtusks grewfrom the palate.Smaller teethlined the jaws.

MASTODON LIZARDMastodonsaurus was a large-headed temnospondyl that belonged to a group of advanced, mostly Triassic animals called capitosaurs. It had a short, massive body, stout limbs, a short tail, and a long-jawedpowerful skull. Two large triangular tusks pointed up from near the tip of its lower jaw. When the jaws closed, these slotted throughopenings on the palate and projected through the top of the skull. The fossils of some smaller temnospondyls bear tooth marks made by Mastodonsaurus-like animals. It probably also ate fish, as well as land-living animals like small archosaurs.

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DURING THE CARBONIFEROUS PERIOD, land-dwelling animals began to diversify and newkinds of terrestrial vertebrates evolved. Lush,forested swamps covered the lowland regionsof the northern continents. Ferns and otherplants formed the understorey, while giant 100-ft (30-m) trees towered overhead. Deadmaterial from these plants built up overmillions of years into thick layers of coal.Humid, tropical conditions and possiblyhigher amounts of oxygen in the atmospherefavored the evolution of giant arthropods,among them huge, dragonfly-like forms andlarge, land-dwelling millipedes and scorpions.Among the vertebrates, temnospondyls andanthracosaurs thrived as amphibious andaquatic predators. On land, lepospondyls andthe first amniotes hunted invertebrate prey.

GIANT ARTHROPODSWith a wingspan of about 28 in (70 cm),Meganeura was one of the largest-ever flyinginsects. It was a swift aerial predator,probably living much like a moderndragonfly. It was not a dragonfly however,belonging instead to a more primitivegroup called the Protodonata. Other giantCarboniferous arthropods includedscorpions more than 24 in (60 cm) long,and Arthropleura, a flat-bodied millipede 6 ft 6 in (2 m) long.

COAL FORMATIONThe decaying tissues of Carboniferous plants built up inlayers as peat. Later, this became compressed andfossilized to produce lignite and eventually coal – a blacksedimentary rock that has been extensively mined for useas a fuel. Plant tissues may not have rotted as quickly inthe Carboniferous as they do today – perhaps becausefungi and microorganisms responsible for decay were not as efficient or abundant as they are now. Early reptiles, such as

Hylonomus, inhabited theCarboniferous forests. Theyprobably foraged in the leaflitter for insects and othersmall prey.




LIFE IN A SWAMP FOREST

Skull and body shapesuggests that Eryopswas an aquatic hunter.

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LIFE IN A SWAMP FOREST

AQUATIC HUNTERSVarious large predatorshaunted the dark waters of the Carboniferous forests,including amphibioustemnospondyls called eryopids(“longfaces”) that survived intothe Permian period. Theirlong, somewhat flattened skullscontained numerous sharpteeth. Eyes and nostrils werelocated on the top of theirheads, suggesting that theykept as much of their bodiesunder water as possible whenstalking prey. They had shortweak limbs, and scaly skinscattered with bony nodules.

CARBONIFEROUS PLANTSA number of plant groups, includingclubmosses, horsetails, and ferns, formedthe Carboniferous swamp forests. Thelargest clubmosses, such as the giantLepidodendron, reached 165 ft (50 m) inheight while the biggest horsetails grew to 50 ft (15 m). Living members of thesegroups are at most a few feet in height.Dense groups of plants would have grownin and around the swampy pools, andbroken stems, branches, and shed leaveswould have lain in the waters.

LONGFACE

Scientific name: EryopsSize: 6 ft 6 in (2 m) longDiet: Fish, amphibious tetrapodsHabitat: Swamps and lakesWhere found: North AmericaTime: Late Carboniferous to PermianRelated genera: Clamorosaurus, Intasuchus

Eryops may havecrawled onto theshore or ontofallen tree trunksto bask or rest.

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LEPOSPONDYLS WERE A GROUP OF CARBONIFEROUS and Permian tetrapodsthat probably included the ancestors of lissamphibians, the group thatincludes frogs, salamanders, and caecilians. They lived in a warm,humid world where giant temnospondyls were the dominant predators.Microsaurs were lizard-like lepospondyls from the Carboniferous andEarly Permian. Some were well-adapted for life on land, while otherswere aquatic. Nectrideans were salamanderlike, and more at home inthe water – the best-known nectridean is Diplocaulus, with its distinctiveboomerang-shaped skull. Lissamphibians evolved early in the Mesozoic,perhaps from microsaurs. Frogs are known from the Triassic, whilesalamanders and caecilians first appear in the Jurassic. Today there are more lissamphibian than mammal species – around 5,000.

BOOMERANG HEADDiplocaulus from the Permian of Texas was one of the mostunusual lepospondyls. The“boomerang” shape of the skull was formed by hornlike extensionsfrom the hind-corners of the back ofthe skull. Baby Diplocaulus did not havethe boomerang-shaped skulls of adults, but as they became older the hornlikestructures became larger. Diplocaulus’ skull was just one of several bizarre designs foundamong nectrideans – several later examplesgrew extremely long snouts. Diplocaulus’ shortbody and tail are also unusual for a nectridean,and some experts have speculated that itpropelled itself by rippling its body up and down, rather than by using its tail.

SNAKELIKE AÏSTOPODSOne of the most bizarre groups of Paleozoictetrapods are the aïstopods, eel-like animalswith more than 200 vertebrae and withoutany limbs or limb girdles. Aïstopods havelarge eyes, suggesting that they hunted bysight. Some may have been able to opentheir jaws very wide, like snakes, and socould have eaten large prey. Scientistsargue over whether aïstopods were aquaticeel-like predators or land-living burrowers. It may be that different aïstopods followedeach of these lifestyles.

LISSAMPHIBIAN DIVERSITYSince their first appearance, lissamphibians have evolved into a wide variety of forms. Frogs are bizarre lissamphibianswith dramatically reduced skeletons. They lack ribs and a tail,have only a few vertebrae, and have a pelvis reduced to a V-shaped structure. Triadobatrachus from Triassic Madagascar

is the earliest known frog. Salamanders firstappear as fossils in the Jurassic, and

modern groups, such as giantsalamanders, are known from theEocene (53–33.7 MYA) onward.The earthworm-like, limblesslissamphibians called caeciliansalso originate in Jurassic times.

Diplocaulus wouldnot have exposed itsvulnerable undersidefor long.

Giant salamander Andrias




Some aïstopods hadextra joints in theirjaws for engulfinglarge prey.

Early frog Triadobatrachus

Aïstopod Aornerpeton

LEPOSPONDYLS AND LISSAMPHIBIANS

Snakelike body with nosign of limbs

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FUNCTION OF THE HEADThe use of Diplocaulus’ horns has been the subject ofmuch speculation. Perhaps predators like temnospondylswould not have been able to swallow Diplocaulus becauseits horns were simply too wide to fit into a predator’smouth. A more ingenious idea is that the hornsfunctioned like an airfoil, generating lift whenDiplocaulus was swimming into a rivercurrent. The animal might have spentmost of its time on the river bottomwatching out for prey, before raisingits head slightly and glidingquickly to the surface to catch a meal.

LEPOSPONDYLS AND LISSAMPHIBIANS

DIPLOCAULUS

Scientific name: DiplocaulusSize: 3 ft (1 m) longDiet: Fish, other vertebrates, crustaceansHabitat: Lakes, rivers, and streamsWhere found: North AmericaTime: Early to Late PermianRelated species: Diplocerapsis

Water passing over thehead travels faster andfurther, creating a drop in downward pressure.

Short tail unlikethat of othernectrideans

Water passing below thehead travels more slowlyand with higher pressure,creating lift.

Relatively weakhindlimbs

Short, wide body may haveallowed Diplocaulus to lieunnoticed on the riverbed

Wide mouth forsnapping up prey

Five-toedfeet

Nostrils

Eyes mounted on top of the skull suggestDiplocaulus spent muchof its life on the riverbed.

Diplocaulus skull and vertebrae

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REPTILIOMORPHSTHE REPTILIOMORPHS, OR “REPTILE FORMS,” include the ancestors of amniotes, and the amniotes – the group that includes reptiles– themselves. Though some specialized reptiliomorphs, likeCrassigyrinus, were amphibious or aquatic, generally theirskeletons became steadily better suited for carrying weight onland. Some reptiliomorphs are found preserved in environmentswell away from water, and are not associated with other water-dependent species. It seems that these terrestrial reptiliomorphswere very amniote-like, and they have at times even beenclassified as amniotes. Whether they actually laid eggs on land, as amniotes do, is still uncertain, but at least some of them areknown to have produced aquatic larvae. Most amphibious andterrestrial reptiliomorphs were sprawling predators that atearthropods and small vertebrates. The terrestrialdiadectomorphs were herbivores, while the long-bodied aquatic anthracosaurs, some of which reached nearly 16 ft (5 m) in length, probably preyed on fish and other animals.

FIRST HERBIVORESDiadectomorphs were reptilelikeanimals that evolved in the Late Carboniferous andsurvived into the Early Permian. They had massive limbgirdles and short, strong limbs. Diadectes from NorthAmerica and Europe is the best known diadectomorph.The shape of their teeth shows that diadectomorphswere herbivores, and thus the very first land vertebratesto evolve a plant-eating lifestyle. Features of theirskeletons show that diadectomorphs were very closelyrelated to amniotes, and they may have been verysimilar in lifestyle and anatomy.




The back part of theskull anchored largechewing muscles.

Diadectes had astout skull anddeep lower jaws.

Front teeth werespoon-shaped andprojected forward.

Short claws withblunt, rounded tips

Molarlike back teeth for chewing

Powerful limbssprawled sidewaysfrom the body.

The tail is unknown,but it was probablylong and used inswimming.

Strong fingers todig up plants

LIZZIE THE LIZARDWestlothiana from the Early Carboniferous ofScotland – nicknamed “Lizzie the lizard” – wasoriginally regarded as the first reptile. It waslater identified as a reptiliomorph only distantlyrelated to amniotes. However, some scientistshave suggested that Westlothiana is not even aclose relation of reptiliomorphs. Instead, it maybe a far more primitive kind of tetrapod (four-footed vertebrate). The same has alsobeen argued for seymouriamorphs.

SEYMOURIAMORPHSThe Permian saw the appearance of the seymouriamorphs, a group of small predatory reptiliomorphs. Many were aquatic, giving birth to young with gills. Like fish, these juveniles had sensory canals ontheir skull bones. Pits on the skulls of Discosauriscus larvae might havehoused organs to detect electrical signals from the muscles of theirprey. Seymouria, from Europe and North America, was a land-basedform. It had stocky limbs and lived in dry upland environments.Unlike those of Discosauriscus, juveniles of Seymouria lacked gills.

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REPTILIOMORPHS

DIADECTES

Scientific name: DiadectesSize: 10 ft (3 m) longDiet: Ferns, mosses, other plantsHabitat: ScrublandWhere found: North America and EuropeTime: Early PermianRelated genera: Desmatodon, Diasparactus



Barrel-shaped bodyprobably housedmassive abdomen.

Toes were shortand composed of stout bones.

Large eyes locatedhigh on the head

The teeth were longand sharply pointed.Large “tusks” grewfrom the palate of theupper jaw.

Skeletal structureof Seymouria

Limb bones wereheavily built andpowerfully muscled.

Lizardlike tail

BIZARRE AQUATIC PREDATORCrassigyrinus from the Early Carboniferous of Scotland is regarded by some experts as a reptiliomorph. It was about 6 ft (2 m) long, with a massive, blunt head and tiny limbs. Crassigyrinus was probably an aquatic predator of fish and other vertebrates. Several of its features were very primitive, perhaps because of its specialization to aquatic life. Among these were its pelvis and a prominent notch in the back of its skull. This may have been for a spiracle – a remnant of the gill slits seen in fish and the earliest limbed vertebrates.

Short tailTiny, virtuallyuseless forelimbs

Westlothiana probablypreyed on insects.

Long,flexiblebody

Limbs show that Westlothiana was suited for life on the ground.

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Cambrian 542–488.3 Ordovician 488.3–443.7

AMNIOTE EGGSAmniotic eggs have a semipermeable shell that protects the embryo from drying out on land. Aninternal membrane called the amnion surrounds theembryo as well as the yolk, the embryo’s food source. A sac called the allantois stores waste material.Development of the embryo in a protective sealedstructure meant that the free-swimming larval stage seen in earlier tetrapods could be dispensed with.

Embryo is protectedfrom the outside worldby the shell.

Microscopic shellpores let gases inand out.

Waste material collects in the allantois.

Yolk feeds the embryoduring development.


INTRODUCING AMNIOTES

Silurian 443.7–416 Devonian 416–359.2


Carboniferous 359.2–299 Permian

IN THE LATE CARBONIFEROUS, a group of animalsappeared that would come to dominate life on land– the amniotes. Descended from reptiliomorphs,these were the first creatures to protect theirembryos within a sealed structure called theamniotic egg. The evolution of amniotic eggs was probably the key development that allowedtetrapods to conquer the land – they could nowmove into environments that were far away fromwater. Amniotes consist of two major groups:synapsids (mammals and their fossil relatives) andreptiles. Many later dispensed with the eggshell and retained their embryos internally, thusaffording them even better protection.

The rotten tree stumps that trapped Hylonomusmostly belonged to Sigillaria, a 100 ft (30 m) tall clubmoss.

Hylonomus wasn’t theonly vertebrate thatperished in these traps.Several species ofmicrosaurs have alsobeen recovered from the tree stumps, as have anthracosaurs and temnospondyls.EARLY FOSSIL AMNIOTES

Paleontologists can identify skeletal features that are unique to synapsids and reptiles, such as their teeth. These features allow them to recognize early fossil amnioteswithout direct proof that they laid amniotic eggs. Theearliest fossil reptiles are Carboniferous animals such as

Hylonomus and Paleothyris. The earliest fossil synapsidis Archaeothyris from thesame CarboniferousCanadian locality asHylonomus andPaleothyris. All theseearly amniotes were verysimilar in appearance.

Skull of Paleothyris

Trapped at thebottom of a hollow tree stump,specimens ofHylonomuseventually died of starvation.

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INTRODUCING AMNIOTES

299–251

MESOZOIC 251–65.5 MYA

Triassic 251–199.6 Jurassic 199.6–145.5 Cretaceous 145.5–65.5

Mud deposits around baseof tree allowed it to grow tomaturity, and were latercompressed into shale.

Paleogene 65.5–23

CENOZOIC 65.5 MYA–present


Floods brought sand into the forest, surrounding and killing the tree. Under pressure, this layer transformed into sandstone.

More than thirty fossil treestumps have now beendiscovered at Joggins.

FOREST MOUSE

Scientific name: HylonomusSize: 8 in (20 cm) longDiet: Millipedes and other arthropodsHabitat: Tropical forest floorsWhere found: Nova Scotia, CanadaTime: Late CarboniferousRelated genera: Paleothyris, Cephalerpeton

Repeated floods allowedsediments to build up around therotting stump, until the ground was level with the top. As floodingcontinued, the stump began to fill with sediments from within.

Hylonomus andother early reptileshad more powerfuljaw muscles thanearlier tetrapods.

Stout skull and sharppointed teeth weresuitable for biting andcrushing small arthropods.

Millipedes and insects fell intothe hollow tree stumps. Thesemay have attracted Hylonomusand other small vertebrateslooking for an easy meal.

SETTING THE TRAPCarboniferous trees were sometimes killed as flood waterscovered their bases with sediment, smothering theirroots. Alternatively, the water may have killed the treesbecause it was salty. Eventually these dead trees rottedand fell over, leaving only a broken stump. The center of the stump then rotted away, and as repeated floodsgradually raised the level of the forest floor around it, the hollow stump eventually formed a pitlike trap. Thelarger animals of Joggins are thought to have fallen intothese traps while fleeing from forest fires. Some of thesecreatures could have survived for awhile by feeding onsnails and arthropods caught in the trap, but eventuallythey would have starved.

LIFE AND DEATHOF HYLONOMUSThe early reptile Hylonomus(“forest mouse”)comes from a famous fossil site calledJoggins in Nova Scotia,Canada. Many specimens are preserved remarkably well as complete skeletons in which the smallest bones,and sometimes even bodyscales, are preserved intact. The superb preservation arises because the skeletonswere preserved inside forest-floor traps formed from rotten tree stumps.

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REPTILES CLADOGRAMDURING THE PALAEOZOIC AND THE MESOZOIC, the clade of amniotescalled the reptiles dominated life on Earth. In the form of birds,snakes, and lizards, reptiles are the most successful group of living amniotes. The earliest reptiles, such as Hylonomus, were tinyinsectivores. However, early parareptiles – a radiation of armouredherbivorous and insectivorous forms – included the largest landanimals of the Permian. Turtles are surviving members of this earlyparareptile radiation. The diapsids – a major reptile group – evolvedlate in the Carboniferous. The Late Permian saw the rise of thearchosaurs – the group that includes dinosaurs, birds, pterosaurs, and crocodiles. Living alongside the archosaurs were the squamates,the diapsid group that includes lizards, snakes, and their relatives.


PARAREPTILES

CAPTORHINIDS AND HYLONOMUS

SAUROPSID OPENINGSReptiles are united by thepresence of two openings in the palate (roof of the mouth)called suborbital fenestrae. The function of these openingsremains obscure. Primitiveparareptiles lack the featuresthat distinguish other reptiles.

CANINE-LIKE TEETHThe captorhinids and moreadvanced reptiles are united bythe presence of canine-like teethin their upper jaws. These teethmay have helped them bite intodifferent types of food, fromanimal prey to parts of plants.

Reptile skull

Hylonomus from theLate Carboniferous

Sauropsidopening

Hylonomus is theearliest-known reptile,and was fully adaptedfor life on land.

Turtles possess protectivearmour plates, like other parareptiles.

Cretaceous marineturtle Archelon

Canine-like teeth in upper jaw

REPTILESSauropsid openings

in the palate

Captorhinid skull

Canine-liketeeth

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MARINE REPTILES

CROCODYLOMORPHSORNITHODIRANS

SNAKES, LIZARDS,AND SPHENODONTS

DIAPSID OPENINGSTypical diapsid reptileshave an upper and lowerhole in the skull behindeach eye socket. Most ofthe marine diapsids lostthe lower hole in thecourse of evolution.

ANTORBITAL FENESTRAArchosaurs, or the “ruling reptiles,”are diapsids that have an opening,called the antorbital fenestra,between the eye socket and thenostril. Living crocodiles have lostthis opening, while birds have it inreduced form.

HINGE-LIKE ANKLEDinosaurs and their relativesare mostly bipedal archosaurswho share a simple, hinge-like ankle joint. Pterosaursshare this type of ankle andmay also be members of theornithodirans.

Ichthyosaurus fromthe Mid Mesozoic

Jurassic crocodileMetriorhynchus

REPTILE EVOLUTIONMany reptile key features signify improvements in catching andbiting food. The canine-like teeth that evolved in the Carboniferousperhaps helped early reptiles grab food, while the evolution ofdiapsid openings may have lightened and strengthened the skull.The antorbital fenestra of archosaurs may have further lightened the skull, allowing faster head strikes. Parts of the reptile cladogramremain controversial. Experts argue over whether marine reptilesare closest to lizards and their relatives or to archosaurs.

REPTILES CLADOGRAM

The diapsid openings may helpreduce the stress placed on theback of the skull during biting.

Diapsid reptile skull

Antorbital fenestraEye socket

Nostril

Riojasuchus skull

Tyrannosaurus foot bones

Ankle joint

Saltasaurus andother dinosaursare ornithodirans.

ORNITHODIRANSHinge-like ankle

ARCHOSAURSAntorbital fenestra

DIAPSIDSDiapsid openings

Lizard

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PARAREPTILESPARAREPTILES WERE A GROUP OF UNUSUAL REPTILES thatincluded small lizard-like forms as well as larger animals,some of them bristling with spikes and armor plates. Unlikemost other reptiles, many parareptiles lacked holes, calledfenestrae, at the back of their skulls. These fenestraehelped to lighten the skulls in more advanced reptiles such as dinosaurs. Many parareptiles appear to have been herbivorous, with blunt, peglike teeth, while othersprobably ate insects and other arthropods. Probably themost primitive group of parareptiles were the lizardlikemilleretids from Late Permian South Africa. Traditionally,turtles – which also lack fenestrae at the back of their skulls – have been included among the parareptiles.

PROCOLOPHONIDSThe procolophonids were parareptiles that lived worldwidefrom the Late Permian to the Late Triassic. They wereshaped like chunky lizards, with broad-cheeked skulls.Their cheeks sported a stout backward-pointing spike,though Hypsognathus, from Late Triassic North America,had several cheek spikes. Procolophon, the best-knownprocolophonid, is unusual in that some species possessedskull fenestrae. More primitive parareptiles did not havethese, so Procolophon must have evolvedthem independently from otherreptiles. Procolophonids had blunt, peglike teeth at theback of their mouths, andmay have eaten toughplants or insects.

ARMORED SKULLElginia was a pareiasaur – a member of a

group of Late Permian parareptiles whichgrew up to 10 ft (3 m) long. Elginia was a

dwarf form, about 2 ft (60 cm) long, foundin Scotland. Its head was covered in

spikes and there were two particularlylong ones growing out of the back of

its skull. These were probably usedfor display rather than combat.Some dwarf pareiasaurs hadextensive body armor and were strikingly turtle-like.

Short tail didnot reach theground.

Conical defensivespikes coveringback

Extra vertebraeattached to hipshelped Scutosaurussupport its bodyweight.




Short, stumpytoes suited forslow walking

Short legs and toessuggest Procolophonwas not a fast runner.

Strong, robustlimbs perhapsused fordigging

Blunt-tipped,short snout

Massive,columnlikehindlimbs forsupportingweight

Skull surfacecovered in lumpsand bumps

FragmentedProcolophon fossil

Large eyessuggest acute vision.

Large, thinhorn

Cheek spikes mayhave been used inshoving matches.

Robust, roundedbody probablyhoused largedigestive system.

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MESOSAURSA sister group to the parareptiles,and all other reptiles, were themesosaurs, small aquatic reptilesfrom Permian times. They hadelongated jaws and needleliketeeth that would have helpedthem strain small fishes andarthropods out of the water.Paddlelike tails, webbed fingers andtoes, and thickened ribs would havehelped them stay below the water surface and maneuver when hunting.

Nasal horndeveloped inadults

Blunt, broad snoutwith broad mouth

Teeth wereserrated, andleaf-shaped inprofile.

Large spikes growing from lower jaw developed with age.

PARAREPTILES

SHIELD LIZARD

Scientific name: ScutosaurusSize: 8 ft (2.5 m) longDiet: Ferns, horsetails, and other plantsHabitat: Marshes and floodplainsWhere found: Eastern EuropeTime: Late PermianRelated genera: Sanchuanasaurus, Elginia

PAREIASAURSGiant pareiasaurs like Scutosaurus (“shield lizard”)wereheavily built parareptiles with massive, rounded bodies.Their teeth were suited for biting and chewing toughfoliage, and their huge bodies probably housed enormousabdomens to digest low-quality plant material. Scutosaurusand its relatives were covered with bony spikes, bosses, and horns. Some of these structures, such as the cheekprojections and nose and jaw spikes, only developed withage and could have been used in mating displays or infights with rivals. The structures could also have beendefensive, as pareiasaurs would probably have been preyed upon by large therapsids and early archosaurs.

Fossil mesosaurs

Large, projecting cheekflanges (platelike projections),perhaps for self-defense

Powerfully muscled,sprawling forelimbs

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TURTLESTURTLES OR CHELONIANS ARE UNIQUE REPTILES that firstappeared in the Triassic as small amphibiousomnivores. During the Mesozoic, they diverged intoland-dwelling herbivores, freshwater omnivores andpredators, and giant, fully marine creatures with adiet of sponges and jellyfish. Today they flourish asmore than 250 species. Although some early turtlesstill had teeth on their palate, all turtles have adistinctive toothless beak. This beak is highlyadaptable, and has been used by various turtle species to cut plant material, strip flesh fromcarcasses, catch fish, and bite poisonous or abrasivefood items like jellyfish and sponges. The origins ofturtles are still controversial. Some experts say thatturtles are parareptiles and that they evolved fromdwarf armored pareiasaurs. Others think that they are highly modified diapsid reptiles.




SHELLSTRUCTUREAll turtles possessa shell – their mostdistinctive feature.Remarkably, the shell is a modified ribcage coveredby armor plates. Unlike any other vertebrate, turtleshave modified their skeleton so that their shoulderand hip girdles are inside their ribcage. Advancedturtles can pull their limbs, neck, and tail insidetheir shell and some forms even have hinges intheir shells allowing them to shut their entirebody away from the outside world. Theearliest turtles, like Proganochelys from Late Triassic Germany, could not drawtheir neck or limbs inside their shell.

The largestmeiolaniids hadskulls more than12 in (30 cm) wide.

HORNED LAND TURTLESThe meiolaniids were an unusual group of giantterrestrial turtles that lived in South America andAustralasia from the Cretaceous to the recent past,and grew up to 8 ft (2.5 m) long. Large horns ontheir skulls pointing sideways or backward andupward meant that meiolaniids could not withdraw their heads into their shells. They alsowielded a defensive bony club on the end of theirtail tip, similar to that of the ankylosauriddinosaurs. One meiolaniid from QuaternaryAustralia is named Ninjemys (“ninja turtle”).Thevery last meiolaniids were still living on Lord HoweIsland in the Pacific Ocean 120,000 years ago.

Interior ofAraripemysshell

MARINE GIANTSeagoing turtles firstevolved in the EarlyCretaceous and are just oneof many groups that developedinto giant forms. Archelon, amongthe biggest of all, reached nearly 13 ft (4 m) long – twice the length of a large modern marine turtle. Turtles nevergrew much larger than this because they still needed tocome ashore and lay eggs, and this meant they had to beable to support their weight on land. In contrast to landturtles, such as tortoises, some marine turtles reduced theweight of their shell and gained buoyancy by losing armorplates and developing a thick leathery covering. However,some species then evolved defensive spikes along the middle ridge of their shells, perhaps to discourage attacksfrom large predators such as mosasaurs and plesiosaurs.

Large sidehorns, perhaps used in fighting.

Nostrils high up on the snout.

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TWO KINDS OF TURTLESEarly in their evolution, turtles split into two groups,depending on how theypulled their necks into theirshells. Pleurodires such asStupendemys and the modernsnake-necked turtles are allfreshwater animals, and pull theirnecks in sideways. Stupendemys, fromSouth America 4 million years ago,was the largest freshwater turtle ever,growing up to 6 ft 6 in (2 m) long.

Cryptodires, which pull their necksin vertically, include tortoises,

marine turtles, and terrapins.

Living relatives ofStupendemys eatwater plants, fruit,and fish.

ARCHELON

Scientific name: ArchelonSize: 13 ft (4 m)Diet: Probably jellyfishHabitat: Warm, shallow seasWhere found: North AmericaTime: Late CretaceousRelated genera: Protostega, Calcarichelys

TURTLES

Archelon’s similarities to modernleatherback turtlessuggest its shell mayhave been covered inthick skin, rather thanarmor plates.

Hind flippersshorter and broader than the front ones

Spaces between the ribs wereprobably visible in the live animal.

Archelon may have beenprey for giant mosasaurslike Tylosaurus.

Male turtles haveshorter tails thanfemale ones.

Stupendemysprobably spent mostof its time in water.

Female sea turtles usetheir hind paddles todig nests.

Of five fingers in the paddle, the third and fourth were the longest.

Large winglikepaddles used forunderwater flight.

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LATE IN THE PERMIAN, THE DIAPSIDS – the reptiliangroup that includes the lizards, archosaurs, andmarine ichthyosaurs and plesiosaurs – underwentan extraordinary burst of evolution. Evolving from small insect-eating ancestors from theCarboniferous, the diapsids soon produced gliders,swimmers, and diggers. Many of these new diapsidsshared special features of the skull and skeleton,and are grouped together as the neodiapsids (“newdiapsids”). Most early neodiapsids were small andinhabited environments where large synapsids,such as dinocephalians and dicynodonts, were the dominant herbivores and carnivores. By thebeginning of the Triassic, many neodiapsids wereextinct, but choristoderes survived throughout theMesozoic and into the Cenozoic. Other neodiapsidgroups were ancestors of the two great reptilegroups of the Mesozoic – the squamates (lizards,snakes, and relatives) and the archosaurs(dinosaurs, birds, crocodiles, and relatives).




Each wing wassupported by 22curving, rodlike bones.

The back of the skullwas very broad but the snout was pointed.

Claws were curved, sharp,and good at grasping.

Sharp, conicalteeth were suited for catching insects.

Back of skull raised upinto a serrated crest

COELUROSAURAVUS

Scientific name: CoelurosauravusSize: 2 ft (60 cm) longDiet: InsectsHabitat: Open forestWhere found: Madagascar and EuropeTime: Late PermianRelated genera: Weigeltisaurus, Wapitisaurus

DIVERSIFYING DIAPSIDS

The back of the skull resemblesthat of lizards. This once ledexperts to think that lizardsdescended from younginiforms.

Youngina had aparticularly long,narrow snout.

YOUNGINA AND RELATIVESThe younginiforms were among the most primitive neodiapsids. They were agile Permian reptiles with short necks and large openings at the back of the skull. Though some younginiforms were aquatic, most were land dwellers. Youngina itself was a burrowing reptile – young specimens have been found preserved together in a fossil burrow, perhaps clustered together to regulate body heat when the weather was too hot or too cold. Thadeosaurus, a younginiformfrom Madagascar, had a strikingly long tail and very long toes. It may have been a fast runner like modern long-tailed lizards.

EARLY GLIDERSThe weigeltisaurids wereunusual tree-dwelling

diapsids. They glided usingskin membranes stretched

over long rods that grew from thesides of the body. These “wings” could be folded away when not in use. Thegliding rods of Coelurosauravus, the best known weigeltisaurid, were at firstmistaken for a fish’s fin spines. When

they were identified as part of Coelurosauravus, they

were thought to beextendable ribs

like those seen on Draco, the modern

gliding lizard of southeast Asia.Recent studies have shown that

the wing struts of weigeltisaurids arecompletely unconnected to the ribs – they are unique features not seen in any other animal, living or extinct.Weigeltisaurids are rather primitive and appear to be separate from the neodiapsids.

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CHORISTODERESThe choristoderes were a group ofaquatic and land-dwelling neodiapsidswhose fossil record extends from theTriassic to the mid-Tertiary. They evolvedfrom younginiform-like ancestors in thePermian. None were bigger than 10 ft (3 m)in length. Some, like Champsosaurus shownhere, looked superficially like river-dwellingcrocodiles, and probably hunted fish.Shokawa from Cretaceous Japan was long-necked, and resembled a miniatureplesiosaur. Short-snouted Lazarussuchuswas also small, but built for life on land.

LIFE IN THE WATERSeveral Permian neodiapsids were

among the earliest reptiles to take tolife in the water, hunting fish and other

prey. The younginiform Hovasaurus fromLate Permian Madagascar had a deepened,paddlelike tail for swimming. Its fossil stomachcontents show that it swallowed stones, perhapsfor use as ballast. Other swimming neodiapsids,like Claudiosaurus, also evolved in the LatePermian. Claudiosaurus may be a close relative of later marine reptiles such as the plesiosaursand ichthyosaurs.

Champsosaurushad longer jawsthan any otherchoristodere.

Skin membranesstretched acrossthe bony rods.

Vertebrae show evidenceof a swimming lifestyle.

Strong forelimb bonescould have been usedin swimming.

The body was longand flattened fromtop to bottom.

Restoration of Hovasaurus

Arms and legs showthat Hovasaurus couldalso walk on land.

DIVERSIFYING DIAPSIDS

TYLOSAURUSThis giant, long-skulled mosasaur was part of a groupof mosasaurs called the russellosaurines. One of themost distinctive features of Tylosaurus was a hard, bonytip to its snout. Tylosaurus may haveused this snout as a ramming weaponfor stunning prey. Some specimenshave been found with damagedsnouts, which suggests that suchbehavior was likely. However, thesnout tip was not made of solidbone, so it was probably morefragile than it looked.

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MOSASAURSLARGE SEA LIZARDS CALLED MOSASAURS dominated the shallowcontinental seas of the Cretaceous. Related to land lizards, such asmonitors and gila monsters, the earliest mosasaurs were amphibiouspredators about 3 ft (1 m) in length. Later mosasaurs grew to morethan 49 ft (15 m) long and were among the most awesome marinepredators of all time. With large, conical teeth and strong jaws, theypreyed on large fish, turtles, and plesiosaurs. Some mosasaurs evolvedblunt, crushing teeth and probably ate shelled molluscs, such asammonites. Because of their size and specialization for life in water, itseems unlikely that later mosasaurs could move on land, so femalesprobably gave birth to live young at sea.

Like modern seacreatures, tylosaursprobably had a darkupper surface and alight underside.




Mosasaurs didnot just haveteeth liningtheir jaws, theyalso had teethon the bonesof their palate.

Some mosasaurshad small, smoothscales. Others hadscales with ridgesacross the middle.

MOSASAUR SENSESLike their lizard relatives onland, mosasaurs probablyhad long forked tongues.Their skulls show that they had theJacobson’s organ, a structure used by snakesand lizards to detect scent particles in air orwater. This indicates that mosasaurs probablyused smell to hunt their prey and to detectother members of their species. All mosasaurshad large eyes and, probably, acute eyesight.

The tip of the lowerjaw was blunt andrectangular.

Bony tipto snout

Spines suggesttail would havebeen deep butnarrow – likethat of a livingsea snake.

Monitor lizard

FLIPPERS AND FINSMosasaurs had evolved streamlined flippers fromthe arms and legs of their land-living ancestors.

Extra finger and toe bones made the flipperslonger. Mosasaurs probably moved their

long, flexible tails from side to side whenswimming, a method called

sculling, and steered withtheir flippers. Long, bony

spines on the tailvertebrae show that

the tail was deep,but narrow

in width.

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A LINK WITH SNAKES?The most controversial area in the study of mosasaurs iswhether or not they were close relatives of snakes. Like snakes,mosasaurs had long, flexible bodies, reduced limbs, and verymobile skull bones. So some experts argue that snakes and earlymosasaurs both descended from the same swimming ancestor.However, other experts argue that snakes are not related tomosasaurs and that the similarities are only superficial.

MOSASAURS

Its powerful tailpropelled Tylosaurusthrough the water.Tylosaurus had long, winglike

flippers. Some mosasaurs hadbroad, paddlelike flippers.

Fossil skeletonof Boavus, anearly snake

TYLOSAURUS

Scientific name: TylosaurusSize: 36 ft (11 m) longDiet: Turtles, fish, other mosasaursHabitat: Shallow seasWhere found: North America, JapanTime: Late CretaceousRelated genera: Ectenosaurus, Platecarpus,Plioplatecarpus

Skeleton of Tylosaurus

Internal spaces in thebones were probablyfilled by fat. Modernwhales also have fattyspaces in their bones.

Mosasaurs hadmobile skull bonesthat would haveallowed them toswallow large prey.


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PLACODONTS AND NOTHOSAURSTHESE TWO GROUPS OF CREATURES were marine reptiles. They wererelated to plesiosaurs and formed part of a larger group called theSauropterygia. Placodonts and nothosaurs were largely restricted tothe warm, shallow seas of Triassic Europe, northern Africa, and Asiaand none of them were particularly large – most were around 3 ft (1 m) long. Nothosaurs were amphibious, long-necked predators withnumerous sharp teeth. Their fossils have been found in sea rocks.This suggests that they were sea-going creatures, but they probablyrested and bred on land, much like modern seals. Placodonts werearmored sauropterygians with teeth suited for crushing shellfish.

NOTHOSAURUSThe best known nothosaur is Nothosaurus. It had a long, narrowsnout and fanglike teeth. Small teeth lined its jaws all the way tothe back of the cheek region. Various species of Nothosaurus havebeen found in Europe, the Middle East, and East Asia. In theEarly Triassic, a rise in sea levels allowed Nothosaurus to invade ashallow sea in what is now Israel. New species of Nothosaurusevolved there, including a specialized dwarf species.

SHELLFISH DIETSome placodonts, such as Placodus, had forward-

pointing peglike teeth. They probably used theseto pluck shellfish from the sea floor. Heavy

bones and bony armor helped placodonts stayon the sea floor when feeding. In addition to

its front teeth, Placodus also had flattenedteeth covering much of its upper palate.

These met with similar teeth on the lowerjaw and formed a crushing apparatusused to break open shellfish.

Nothosaurus had tallvertebral spines inthe shoulder region.



A nothosaur’sshoulder and chestbones formed large,flattened plates.

Upper jawof Placodus

Flattenedteeth forcrushing food

The lower jaw teethwere wide androunded.

Long, pointedfront teeth

Smaller teeth at theback of the jaw

Peglike teethstuck out ofthe front ofthe jaws.

Lower jawof Placodus

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Nothosaurus’s hips werestrongly connected to itsbackbone. This was nottrue of all nothosaurs.

Like moreprimitive reptiles,nothosaurs hadlong, flexible tails.

Nothosaurus probablymoved its tail from sideto side when swimming.

NOTHOSAURUS

Scientific name: NothosaurusSize: Different species ranged from 3–10 ft (1–3 m) in length.Diet: FishHabitat: Shallow tropical seasWhere found: Europe, Near EastTime: TriassicRelated genera: Germanosaurus, Lariosaurus

PLACODONTS AND NOTHOSAURS

Unlike plesiosaurs,nothosaurs hadflexible knee andankle joints.

Powerful limb muscleswere attached to theunderside of the body.

Its fingers andtoes may havebeen webbed.

Henodus had no teeth.It may have filtered itsfood out of the water.

REPTILIAN RAYSPlacochelyids, such as this Psephoderma, were turtlelikeplacodonts with long, whiplike tails, paddle-shapedlimbs, and sharply pointed snouts. Their body shapewas similar to that of rays, a group of fish that firstappeared in the Jurassic. Like rays, placochelyids

might have hidden underneath sand or gravel onthe sea floor. They probably foraged for shellfish.

HENODUSIn some placodonts, the body armorbecame very extensive and formed ashell resembling that of a turtle.Henodus was a particularly turtlelikeplacodont. It lived in a lagoonlikesea where the water would havebeen slightly salty. Living inthis kind of water is difficultbecause any changes in thesalt levels are stressful toanimals. Shelled animals,such as turtles and Henodus,are better equipped to cope with this stress.

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SHORT-NECKED PLESIOSAURSPLESIOSAURS WERE MARINE REPTILES. They belonged to the same groupas nothosaurs and placodonts, the Sauropterygia. All plesiosaurs hadfour winglike flippers and many pointed teeth. They probably usedtheir flippers to “fly” underwater in a similar way to marine turtles orpenguins. While many plesiosaurs had long necks and small skulls,others, the pliosaurs, were short-necked and hadenormous skulls. The biggest pliosaurs, such asLiopleurodon and Kronosaurus, had skulls 10 ft (3 m)long with huge pointed teeth. It seems likely thatpliosaurs were predators that fed on other marinereptiles. This is confirmed by long-necked plesiosaurskeletons that bear pliosaur tooth marks.

SOUTHERN HEMISPHERE GIANTKronosaurus was a giant pliosaur from Australia andSouth America. It is best known from the reconstructedskeleton displayed at the Harvard Museum ofComparative Zoology in Massachusetts. This measures43 ft (13 m) from nose to tail, with a very long body. Its immense skull supports a massive bony crest. Recentwork has shown that this reconstruction is inaccurate:there should not be a huge skull crest and the bodyshould be shorter, meaning that Kronosaurus wasprobably only about 30 ft (9 m) long. Pliosaurs likeKronosaurus lived worldwide throughout the Jurassicand Cretaceous periods.

UNDERWATER SNIFFINGPlesiosaurs’ internal nostrils – two holes on the palate – arelocated farther forward than the nostrils on the outside ofthe snout. This suggests that water flowed through the snoutand into the internal nostrils, where scent particles couldhave been detected, then out through the external nostrils.Plesiosaurs could therefore have “sniffed” the water theyswam through, as modern sharks do, to detect prey.

The flippers wereformed of longfingers and toeswith numeroussmall bones.

Maybe pliosaurs like thisSimolestes were notclose relatives of formslike Kronosaurus.

The large eyes faced slightlyforward, suggesting anoverlapping field of vision.




External nostrils

The biggest teeth were 10 in (25 cm) long but muchof this length was embeddedin the bones of the jaw.

WERE PLIOSAURS A NATURAL GROUP?Several different pliosaur groups are known. Theseinclude rhomaleosaurs, pliosaurids, brachaucheniids(which may include Kronosaurus), and polycotylids. Allof these groups might share the same single ancestor,and therefore form a clade. Alternatively, differentpliosaurs might descend from different long-neckedplesiosaur ancestors. Plesiosaur experts still argue overthese opposing views.

Water enters mouthand flows into theinternal nostrils.

Skull of Plesiosaurus

Water leaves skullthrough the externalnostrils.

Large eyesocket

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PLIOSAUR STOMACH CONTENTSThis photograph shows quartz grains and ahooklet from a squid found in a pliosaur’sstomach. We know from their stomach contentsthat pliosaurs preyed on all kinds of marineanimal, from small fish and squid to otherplesiosaurs. One pliosaur specimen evenappears to have swallowed armor plates from a thyreophoran dinosaur. Pliosaurs may haveeaten floating dinosaur carcasses, or perhapsthey grabbed swimming dinosaurs or those thatgot too close to the water’s edge.

Unlike terrestrial reptiles,in plesiosaurs the bonesof the shoulder and hipgirdles were located onthe underside of the body.

All plesiosaurs hadbelly ribs, or gastralia,that were tightlyinterlocked and helpedto keep the body stiff.

Pliosaurs had short tails thatwere probably not used formoving around. Some fossilssuggest that there may havebeen a diamond-shaped finat the tip of the tail.

Massive muscles gave theflippers a very powerfuldownstroke. Perhaps whileone pair of flippers was inthe downstroke, the otherpair was in the upstroke.

In pliosaurs thehind pair offlippers were largerthan the front pair.

Kronosaurus

SHORT-NECKED PLESIOSAURS

KRONOSAURUS

Scientific name: KronosaurusSize: 30 ft (9 m) longDiet: Marine reptiles, fish, and mollusksHabitat: Open oceanWhere found: Australia and South AmericaTime: Early CretaceousRelated genus: Brachauchenius



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LONG NECKSElasmosaurus had 72 vertebrae in its neck, more than any other plesiosaur, or indeed any other animal.Studies of plesiosaur vertebrae suggest that their neckswere fairly flexible, but experts are still unsure how theyused them. Elasmosaurus may have approached a shoalof fish from behind and used its neck to plunge itshead into them, or it may have “flown” slowlyabove the sea floor, using its neck toreach down and graze on bottom-dwelling invertebrates.

PLESIOSAUR SKULLSCompared to the sizes of their bodies, long-neckedplesiosaurs had small skulls. The shape of the bony ring that supported the eyeball suggests thatplesiosaurs had flattened eyeballs, so their eyeswould have been better suited to seeing underwaterthan in air. Some plesiosaurs have been found withearbones. These are fused to the surrounding skullbones, which suggests that their ears were not suitedto detecting sound waves carried through the air.

LONG-NECKED PLESIOSAURSWHILE SOME PLESIOSAURS were big-headedpredators, others had small skulls and very longnecks. One group of plesiosaurs, the elasmosaurs,had necks up to 16 ft (5 m) long. Most long-neckedplesiosaurs fed on fish and mollusks, though somemay have eaten seafloor invertebrates and othersperhaps preyed on other marine reptiles. Bothshort- and long-necked plesiosaurs became extinct by the end of the Cretaceous.

FILTER FEEDING PLESIOSAURSOne group of long-necked plesiosaurs, thecryptoclidids, had numerous interlockingneedlelike teeth. These were probably usedas a filtering device to capture small fish andswimming shrimps. The cryptoclidid wouldhave closed its mouth around a group of preyand then pushed the water out of its mouthwith its tongue. Any small animals in itsmouth would have been trapped there by the interlocking teeth.



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LONG-NECKED PLESIOSAURS

PLATE LIZARDElasmosaurus was a Late Cretaceousrepresentative of the elasmosaurs, a group of long-necked plesiosaurs that originated inthe Jurassic. Like all advanced elasmosaurs,Elasmosaurus had a tremendously long neck,a light skull lined with vicious interlockingteeth, and winglike flippers with slim pointedtips. The name Elasmosaurus means “platelizard” and comes from the large, platelikeshoulder bones that covered its chest andformed its arm sockets. The huge musclesthat powered its flippers were anchored to these bones.

PLATE LIZARD

Scientific name: ElasmosaurusSize: 46 ft (14 m) longDiet: Fish and swimming mollusksHabitat: Shallow seasWhere found: North AmericaTime: Late CretaceousRelated genera: Callawayasaurus, Libonectes

SHARK–SHAPED REPTILEIchthyosaurus is one of the best known of allichthyosaurs and many specimens have been found in Jurassic rocks in England and Germany. Like othermembers of the advanced group of ichthyosaurscalled thunnosaurs, Ichthyosaurus had a shark-shapedbody. It was a medium-sized ichthyosaur, with a slim,pointed snout and fore flippers twice as large as itshind flippers. Ichthyosaurus had very broad front finswith six or more digits. Some later ichthyosaurshad even more digits than this. Platypterygiusfrom the Cretaceous, for example, hadeight or more.

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ICHTHYOSAURSTHESE MESOZOIC MARINE REPTILES are famous for resembling sharks or dolphins. Many ichthyosaur fossils have been found, some of whichhave impressions of the skin preserved. These show that advancedichthyosaurs, such as Ichthyosaurus, had a triangular dorsal fin, twopairs of paddlelike fins, and a forked, vertical tail like that of a shark.Long, snapping jaws and conical teeth suggest that ichthyosaurs atefish and squid. This has been confirmed by their stomach contents.While the smaller ichthyosaurs were only about 3 ft (1 m) long, giantichthyosaurs from the Triassic and early Jurassic grew to more than 65 ft (20 m) in length, making them the second largest marinereptiles after pliosaur giants. Ichthyosaurs were already rare in theCretaceous and did not survive to the end of the Mesozoic.

BIRTH AND BABIESSome ichthyosaurs have beenfound with the bones of babiespreserved in their abdominalregion. At first, experts thoughtthat these babies were stomachcontents and therefore evidenceof cannibalism. But it is nowclear that these were babies thatdied before or during birth. Mostpregnant ichthyosaurs preserveonly one or two babies, thoughsome have as many as 11. Thebabies were born tail-first andfully able to swim.

Skeleton of Stenopterygius

Ichthyosaurus




This ichthyosaur fossil ispreserved with the babiesstill inside the mother.

Small, pointedteeth forgrabbing fish

Ichthyosaur earbones are not separated from the otherskull bones, as they are indolphins, so there is no reasonto think that they used sonar.

Long, slim jaws forsnapping up fish andswimming mollusks

In all chthyosaurs thenostril was positionedclose to the eye.

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BIG EYES AND DEEP DIVINGIchthyosaurs had huge eye sockets, filled by a ring of bones calledthe sclerotic ring. This helped support the massive eyeball. Theirlarge eyes suggest that ichthyosaurs used eyesight to hunt. Theymay have been able to hunt prey at night, in murky waters, or in perpetually dark, deep waters. Temnodontosaurus, a Jurassicichthyosaur from Europe, had the largest eyes of any vertebrateanimal. Each of its eyes was 10 in (26 cm) wide.

Fossil of Stenopterygius

ICHTHYOSAURS

Impressions ofichthyosaur dorsalfins show that theywere triangular in shape.

Preserved ichthyosaurskin is smooth andapparently without scales.

Skin impressions showthat ichthyosaurs had anupper lobe to their tails.

HOW DID ICHTHYOSAURS SWIM?Experts argue over how exactly ichthyosaursswam. They probably used their forked tails to propel them through the water.Stiffening fibers helped the tail base to actas a hinge, so that the tail could be flappedrapidly from side to side. Their powerfulshoulders and wing-shaped flippers suggestto some experts that ichthyosaurs flappedtheir flippers and “flew” underwater.

ICHTHYOSAURUS

Scientific name: IchthyosaurusSize: 10 ft (3 m) longDiet: Fish and squidHabitat: Open oceanWhere found: EuropeTime: Early JurassicRelated genus: Stenopterygius


The small hind fins mayhave acted as stabilizers,helping the animal tostay upright.

The bones at the endof the tail grewdownward to supportthe tail’s bottom lobe.

Baby ichthyosaurs hadproportionally largerheads and shorterbodies than adults.

Enormous eye withhuge bony ring


Skull of Ichthyosaurus

GIRAFFE-NECKED FISHERThe prolacertiformTanystropheus was amongthe most peculiar of allTriassic reptiles. Manyprolacertiforms had long necks,but in Tanystropheus this was taken to anextreme, and its neck was twice as long asits body. Tanystropheus had only about 10very long vertebrae in its neck, whichsuggests that its neck was not very flexible.Most specimens of Tanystropheus arepreserved in marine rocks, so itprobably either fished fromthe water’s edge or swam.

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Cambrian 542–488.3 Ordovician 488.3–443.7

EARLY RULING REPTILE GROUPS


Lizardlike body shape

Skeleton of Trilophosaurus

TRILOPHOSAURSExperts know from their skeletons that trilophosaurs werearchosauromorphs, but they are unusual because, unlikeother members of the group, they had grown new bone overthe lower of the two diapsid skull openings. Trilophosaurshad robust skulls and toothless, beaklike snout tips. Theyhad broad teeth for slicing and chewing tough plants.

All trilophosaurs wereless than 3 ft 3 in(1m) in length.

Long limbssuited to runningand digging

ARCHOSAURS – THE GROUP OF ANIMALS that includes crocodiles,dinosaurs, and birds – belong to a larger group called thearchosauromorphs, or “ruling reptile forms.” During thePermian and Triassic, several archosauromorph groupsevolved. Some, such as the prolacertiforms, were four-leggedmeat eaters that resembled long-necked lizards. Others, suchas the trilophosaurs and rhynchosaurs, were plant eaters whoseskulls and teeth were suited to slicing tough plants. All earlyarchosauromorphs were extinct by the end of the Triassic.

Tanystropheus hadlong, slender limbs.Its hands wereproportionally small.

Lizardlike body shape

Fracture lines in the tail bones suggest thatTanystropheus‘s tailcould break off whenbitten by a predator.

Stout skullwith toothlesssnout tip

Tanystropheus had longfeet and its toes may havebeen webbed. It probablyused its feet for swimming.

Silurian 443.7–416 Devonian 416–359.2 Carboniferous 359.2–299


Permian

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EARLY RULING REPTILE GROUPS

TINY TREE-DWELLERSOne group of prolacertiforms, the megalancosaurs, probablylived in the trees. They were small – less than 1 ft (30 cm)long – and, like living chameleons, had pincerlike hands andtails that could grasp branches. Megalancosaurs had long,slender necks and pointed skulls. Their small, pointed teethsuggest that these reptiles ate insects. Strangely, they had a pointed hook at the tip of their tails.

Skull of Scaphonyx


Hooked beak

Pointed hook

Tanystropheus

Young specimens showthat Tanystropheus’s neckgot proportionally longeras it got older.

Muscles at the back of the skull would havegiven Tanystropheusa short, snapping bite.

Sharp, pointedteeth well suitedfor grasping fish

The neck was strengthenedby long neck ribs, whichgrew backward andoverlapped one another.

Megalancosaurus

TANYSTROPHEUS

Scientific name: TanystropheusSize: 10 ft (3 m) longDiet: Fish and crustaceansHabitat: Shallow seas and shorelinesWhere found: EuropeTime: Middle TriassicRelated genera: Macrocnemus, Tanytrachelos

HOOK-BEAKED PLANT EATERRhynchosaurs were Triassic archosauromorphs with barrel-shaped bodies, short, stout legs, and a downcurved beak at thetip of the upper jaw. They ranged from about 1ft to 6 ft 6 in (30 cm to 2 m) in length. The skull of a rhynchosaur such asScaphonyx shows that when its mouth was shut, the lower jawslotted into grooves in the upper jaw. The jaws and their rows ofblunt, rounded teeth show that rhynchosaurs ate tough plants.

Triassic 251–199.6 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Paleogene 65.5–23 299–251

EARLY CROCODILE-GROUP REPTILES

DEEP-SKULLED GIANTSMany crocodile-group reptiles

were large, land-living predators, called rauisuchians. They had long limbs

and deep skulls with long, serrated teeth. Somewere huge, reaching lengths of up to 33 ft (10 m).

Prestosuchus, shown here, was a rauisuchian fromTriassic Brazil. Similar rauisuchians lived in Europe,Argentina, and elsewhere. Prestosuchus reached about 16 ft (5 m) in length and had a distinctivedownward bend at the tip of its snout.

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ARCHOSAURS AROSE IN THE LATE PERMIAN and, during the Triassic Period,diversified into crocodylomorphs, pterosaurs, dinosaurs, and theirrelatives. Early on, archosaurs split into two clades, both of which haveliving representatives. Ornithodirans included pterosaurs, dinosaurs, and birds. Crocodylotarsians, the crocodile-group reptiles, includedextinct groups and crocodiles’ ancestors. Unlike dinosaurs and theirrelatives, crocodile-group reptiles had ankle joints that allowed them totwist their feet to the side when walking. These joints gavecrocodylotarsians their name, which means “crocodile ankle.” In theTriassic, amphibious, long-jawed crocodylotarsians called phytosaursdominated waterways, while, on land, predatory rauisuchians andplant-eating aetosaurs were important. Yet, despite theirsuccess, all crocodylotarsians exceptcrocodylomorphs became extinct at the endof the Triassic.

HOW RAUISUCHIANS WALKEDRauisuchians’ limbs were positioned directlyunderneath their bodies, perhaps enablingthem to run faster. This evolved in a differentway from dinosaurs and their relatives. Indinosaurs, the top of the thigh bone was turnedinward to meet the hip socket, allowing anerect posture. But rauisuchian thigh bones didnot have an inturned head, so they supportedthe hips from directly underneath.

Two rows of armor plates ranalong the top ofthe spine.

Front viewof hip joint

Pubicbone




The short fifthtoe was turnedbackwards

Thighbones

Thigh bonedirectlyunder hip

Ilium

Ilium

Pubicbone

Side view ofrauisuchianhip joint

Ischium

Large musclesconnected the tailto the thigh bone.

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ARMORED PLANT-EATERSAetosaurs were large crocodile-groupreptiles related to rauisuchians. Their leaf-shaped teeth suggest that they were plant-eaters, and their blunt upturned snouts couldhave been used to dig up roots. Aetosaurs had manylarge armor plates covering the whole upper surface of their bodies and encasing their tails and bellies.Some aetosaurs, such as Desmatosuchus, also had largespikes or horns growing from the sides of their bodies.

Long, powerfuljaws with sharppointed teeth

EARLY CROCODILE-GROUP REPTILES

CROCODILE MIMICSPhytosaurs such as this Machaeroprosopus were amphibious LateTriassic crocodylotarsians. Although they looked like moderncrocodiles, phytosaurs were in fact among the most primitive ofcrocodylotarsians and evolved long before crocodiles. The namephytosaur, meaning “plant reptile,” is very misleading – theirsharp, pointed teeth and snapping jaws clearly show thatphytosaurs were predators.

PRESTOSUCHUS

Scientific name: PrestosuchusSize: 16 ft (5 m) longDiet: Large vertebrates such as dicynodonts,cynodonts, and rhynchosaursHabitat: Scrubland, open woodlandWhere found: BrazilTime: Late TriassicRelated genera: Saurosuchus, Ticinosuchus

The nostrils weresituated on a bumpin front of the eyes.

Powerful leg bones suggest thatPrestosuchus couldrun at high speeds.

PrestosuchusBackward curving,serrated teeth

Short, fairlystraight neck

Desmatosuchus wasabout 10 ft (3 m) long.

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CROCODYLOMOPRHSAPART FROM BIRDS, CROCODYLOMORPHS are the last survivors of the archosaurs or “ruling reptiles” – the group to which the dinosaurs belonged. They evolvedat about the same time as the dinosaurs and for most of their 200-million-yearhistory crocodylomorphs have been large, long-bodied, aquatic carnivores.Armor-plating in the form of bony scutes set in their hides, deep tails, short,strong limbs, and powerful, sharp-toothed jaws made them formidablepredators. Lying loglike in a lake or river, they seized passing fishor ambushed large creatures coming for a drink. In theAge of Dinosaurs, when climates everywhere were warm, these cold-bloodedcreatures spread throughoutthe world. Some becamesuited for life on land,others for life at sea.Some were fast runners,no bigger than a dog,but one monster,Deinosuchus, was as heavy as anelephant andas long as a tenniscourt is wide.

SEA BEASTMetriorhynchus was a

seagoing crocodylomorphfrom the Mesozoic. Its webbed

toes and fingers formed paddlesfor efficient swimming, and its jaws

bristled with razor-sharp teeth forseizing slippery fishes and prehistoric

relatives of squid. Lacking the heavyarmor typical of other crocodylomorphs

Metriorhynchus was quite light and flexible.It probably lay with its nostrils above water,

ready to launch an attack, and hunted bymaking sudden rushes after slowly swimming

up on unsuspecting prey or waiting in ambush.From time to time, it would have hauled itselfashore to lay eggs on sandbanks and perhaps to bask in the warm sun.

Slender jaws




SLENDER-JAWED FISH EATERGharials, also known as gavials, are large, livingcrocodylomorphs. Their long, slender jaws armedwith small but sharp teeth are ideal for catching fish.With relatively weak legs they are poor walkers andseldom venture far from water. Gharials now liveonly in the north of the Indian subcontinent, buttheir genus, Gavialis, goes back 50 million years and was once spread throughout Africa, Asia, and North and South America.

Small but sharp teeth

Forelimbsshaped likehydrofoils

Male has a knob at thetip of his slender snout

Skull broaderbehind the eyesthan in front

Limbs designedto steer andbrake

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MESOZOIC 251–65.5 MYA CENOZOIC 65 MYA–present

METRIORHYNCHUS

Scientific name: MetriorhynchusSize: 10 ft (3 m) longDiet: FishHabitat: SeasWhere found: Europe and South AmericaTime: Mid-Jurassic to CretaceousRelated genera: Geosaurus, Pelagosaurus

CROCODILIANS

LIGHTWEIGHT LANDLUBBERProtosuchus (“first crocodile”) fromEarly Jurassic Arizona was one of theearliest land-based crocodylomorphs.About 3 ft (1 m) in length, this agile huntercould run semi-upright on its long hind legs and wasable to catch speedy lizards and mammals. Its agility onland is still shown by modern crocodiles, which can lifttheir bodies off the ground to walk briskly. Protosuchushad short jaws that broadened out at the base of theskull to maximize the surface to which muscles couldattach. This gave it a powerful bite. When its jawsclamped shut, the pointed canine teeth on its lower jawslotted into sockets in the upper jaw to lock the bite.

Deinosuchuslived to an age of about 50 yearsold, growingthroughout its life.

Downturnedtail

Tail lashed fromside to side toswim forward

Hind limbsmuch longerthan front limbs

Tail protected by two rows ofarmored plates

Relatively broad,short head

Broad, powerfulsnout

TERROR OF THE DINOSAURSDeinosuchus (“terrible crocodile”) was an earlyalligator and may have been the largestcrocodylomorph that ever lived. Up to five timeslarger than today’s species, this Late Cretaceousgiant from North America grew to 33 ft (10 m) inlength and weighed 5 tons (5 tonnes). Lying nearthe water’s edge, Deinosuchus probably lunged toseize large prey, such as duck-billed dinosaurs,before spinning them over and over in the water to tear off great lumps of flesh. Like moderncrocodiles, Deinosuchus is thought to have swallowedstones which served as ballast in the water.

PTEROSAURS WERE FLYING ARCHOSAURS that may have been closely relatedto dinosaurs. A pterosaur’s wings were made of a large skin membranethat stretched from the end of its incredibly long fourth finger to itsbody and back legs. This wing membrane was reinforcedwith stiffening fibers and muscles. Exceptional fossilsshow that some pterosaurs had furry bodies andmay have been warm-blooded, like modernday birds and mammals. Early toothedpterosaurs from the Triassic andJurassic differ from later pterosaurs inhaving long tails, unfused bones in theirbacks, and relatively short bones in theirwrists. Most early pterosaurs were smallcompared to later types, and none had a wingspan of more than 10 ft (3 m).

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PRIMITIVE PTEROSAURSThe earliest pterosaurs are from the Triassic.Though they are primitive compared to laterforms, having shorter wing bones for example,they are still true pterosaurs. One possible“proto-pterosaur” has been found – a Russianfossil called Sharovipteryx. While clearly not apterosaur, it shares many features in commonwith them. Dimorphodon, shown here, was an Early Jurassic pterosaur, notable for itsenormous skull and differently sized teeth. Theteeth at the front of its skull were much largerand more pointed than the others, while theteeth at the back of its lower jaw were tiny.

ANUROGNATHIDSOne early pterosaur group, theanurognathids, had short tails likeadvanced pterosaurs, but still hadthe short wrist bones and otherfeatures of early pterosaurs.Anurognathids had short, tall skulls,sharply pointed teeth and long, slimwings. These features suggest thatthey were fast-flying predatorsthat fed on insects.

Fossil skeletonof Dimorphodon

Like birds, allpterosaurs probablyhad beaks.

Dimorphodon




Anurognathussnapped up insectsin its huge beak.

EARLY PTEROSAURS

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BIRDLIKE SKULLSophisticated flight requires good vision and a well-developedsense of balance. All pterosaur skulls have huge eye sockets,showing that their eyes were large and their eyesight wasprobably excellent. Some pterosaur skulls have internal casts

of their brains preserved. These show that the parts of thebrain responsible for sight and control of movement

were well-developed and similar to the same partsof the brain in modern birds.

EARLY PTEROSAURS

Experts disagreeabout whetherpterosaur wingmembranes wereconnected to thewhole leg or just to the thigh region.

The wing finger wasmade of four long,rodlike bones.

FISH GRABBERSThis fossilized skeleton of the Jurassic pterosaurRhamphorhynchus was found in Germany with skinimpressions and the wing membranes preserved.These show that it had a throat pouch and a diamond-shaped structure on the end of its tail. Rhamphorhynchus had a beak with severalprominent, forward-pointing teeth at the tips ofboth upper and lower jaws. This would have allowedit to snatch fish from the surface of the water.

DIMORPHODON

Scientific name: DimorphodonSize: Wingspan 4–8 ft (1.2–2.5 m)Diet: Fish, insects, and small land animalsHabitat: Seashores, riverside woodlandWhere found: Europe and North AmericaTime: Early JurassicRelated genus: Peteinosaurus

The bones inDimorphodon’s flexibleneck were lightenedby air-filled sacs.

Dimorphodon’slong tail wasstiffened bybony rods.

Sharp hand clawsand a graspingfifth toe show thatDimorphodon wasprobably good at climbing.



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DIMORPHODONRemains of Dimorphodon and related pterosaurshave been found in both seafloor and riversideenvironments, so they may have lived in a varietyof different habitats. Dimorphodon and its relationswere probably opportunistic predators who preyedon a wide variety of small animals. They may haveeaten insects, caught lizards and other smallreptiles, and captured fish and crustaceans fromrivers or the sea. Experts do not know whetherpterosaurs like Dimorphodon caught their prey while aloft, or while standing on all fours.



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EARLY PTEROSAURS

WINGS AND NO TEETHPteranodon, meaning “wings and no teeth,” is one of the mostfamous pterosaurs. UntilQuetzalcoatlus wasdescribed in 1975, Pteranodonwas the largest pterosaur known. It had a large headcrest, and the shape of itslower jaw suggests that Pteranodon had apouch under its bill, something like thatof a pelican. Several species of Pteranodonhave been identified, all of them found in North America.

PTERODACTYLOIDS WERE ADVANCED PTEROSAURSthat first evolved in the Late Jurassic. Asearlier kinds of pterosaurs became extinct,they came to dominate the Cretaceous skies.Some pterodactyloids were toothless, whilesome had hundreds of bristlelike teeth. Other pterodactyloids had huge interlockingteeth for grabbing fish, while a group calleddsungaripterids had blunt teeth, perhaps used for crushing shellfish. Only one or two species of pterodactyloid were left by the end of the Cretaceous. These were the last of the pterosaurs. Pterosaurs may havedeclined because newly evolving waterbirdstook over their habitats.

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ADVANCED PTEROSAURS


Pteranodon ingens had a long, backward-pointing,triangular crest.



Female

Bristleliketeeth

PTERODAUSTROSome pterodactyloids had long jaws and hundreds of slim teeth. The best example is Pterodaustro from EarlyCretaceous South America. Its jaws curved upward and its lower jaws were filled withabout 1,000 straight, bristleliketeeth. It probably strained beak-fuls of water through theseteeth, leaving plankton trapped in its mouth.

MALES AND FEMALESDifferent specimens ofPteranodon have differently

shaped head crests. Some have a large, veryprominent crest – others

a small crest. These two kindshave been found together, so itseems that they are males andfemales of the same species.The males are probably theones with the bigger crests.They probably used their crests to impress females and intimidate other males.

Pterodaustro probablywaded on all fours when feeding.

One Pteranodon fossilhad fish bones preservedwhere its throat pouchwould have been.

Pteranodonsternbergi

Male

WINGS AND WRISTSThe main part of the pterosaur

wing skeleton was an elongated fourthfinger, composed of four bones. A bone

called the pteroid, unique to pterosaurs,pointed forward and inward from the front

of the wrist joint. It supported an extra wingmembrane called the propatagium. This stretched

from the wrist to the shoulder and would have beenused to help control the flow of air over the wing.

Wing bones ofRhamphorhynchus

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GLIDING GIANTSAzhdarchids had long, toothless beaks, long necks, and immensewingspans. Quetzalcoatlus, the best known azhdarchid, had a wingspan of 36 ft (11 m). It was originally suggested thatazhdarchids were vulturelike scavengers. This now seems unlikely,given the shape of their beaks and the restricted movement intheir necks. They probably ate fish and other animals that theypicked up from the surface of the water or from the ground.

ADVANCED PTEROSAURS

Anhanguera

Pteranodon ingens



Gnathosaurus

PTERANODON

Scientific name: PteranodonSize: Wingspan 23–30 ft (7–9 m)Diet: FishHabitat: Shallow intercontinental seasWhere found: North AmericaTime: Late CretaceousRelated genera: Ornithostoma, Nyctosaurus

Quetzalcoatlusin flight

Pteranodon had awingspan of up to 30 ft (9 m).

Pteranodon ingens

Pteranodon’s legs were small and hadweak muscles.

Wing bone

The wing membrane wasstiffened by many thinrods called aktinofibrils.

Tropeognathus

Dsungaripterus

Germanodactylus

CRESTS AND THEIR FUNCTIONSMany pterodactyloids had crests on their skulls, and sometimeson their lower jaws as well. These crests may have been used in courtship displays or as rudders or stabilizers during flight.Some exceptional fossils from Brazil and Germany reveal soft-tissue extensions of the bony crests. These show that, in life, the outline of a pterodactyloid’s crest would have lookeddramatically different from the shape of its skull.

Unlike earlier pterosaurs,pterodactyloids had ashort fifth toe.

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101

Dinosaurs and BirdsA bee-sized hummingbird seems worlds apart

from a dinosaur as heavy as a whale. Yet birds

almost certainly evolved from feathered dinosaurs.

This section brings to life those ancient reptiles

that between them dominated life on land for an

astonishing 160 million years. Realistic models,

many shown in prehistoric settings, reveal

dinosaurs’ likely shapes, colors, and weaponry.

The fantastic range includes armor-plated

herbivores and theropods with jaws big enough

to swallow people whole, had people existed. Read

on to discover how small theropods gave rise to

birds with teeth and claws, and how these clumsy

flyers evolved into today’s aerial acrobats.

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DINOSAURS DEFINED

WHAT MAKES A DINOSAUR?Paleontologists can tell a dinosaur apart from other kinds of fossil animal by details in the bones of its skull,upper arms, hips, thighs, shins, and ankles. We know thatdinosaurs walked with limbs erect and on their toes, notflat-footed like bears. Without living specimens to study, wecannot know for sure just how their bodies worked, butsuch active animals were almost certainly warm-blooded.Small kinds probably generated internal heat as birds andmammals do. Large ones were simply too big to cool downat night. Neither kind grew sluggish in the cold likeordinary reptiles, so dinosaurs were always ready to hunt forfood or find a mate.

DINOSAUR STANCEOne of the keys to dinosaur successwas their upright posture. Mostreptiles sprawl with their legs at theside of their bodies, but dinosaurscarried their limbs directly belowtheir bodies, just like modernmammals, so their weight wascarried straight down. Since theydid not have to use large amountsof energy just to keep their bodiesoff the ground, dinosaurs were freeto develop more active lifestyles.

DINOSAURS AND BIRDS

Cnemial crest(ridge) on tibia

Erect stance ofmammals anddinosaurs

Sprawling postureof most reptiles

Fourth finger(where present)had three orfewer bones.

Long crest onhumerus (upperarm bone)

Femur (thighbone)has a ball-shapedhead turnedinward to slot intohipbones.

Fully openacetabulum toreceive femur

Ridge aboveacetabulum (hole inhipbones) rests onhead of femur.

Allosaurus, a lizard-hipped dinosaur

Almost all dinosaurs havethree or more sacralvertebrae (vertebraelinked to hip girdle).

THE MESOZOIC AGE IS OFTEN CALLED the “Age of theDinosaurs,” because for more than 150 million years, asingle, extremely diverse group of reptiles dominatedlife on land. The first dinosaurs were probably two-legged hunters no bigger than a dog, but they soonevolved into a huge variety of shapes and sizes, andspread around the world. In time, they came to rangefrom giants as heavy as a great whale to little birdlikebeasts no bigger than a hen. No individual dinosaurspecies lasted longer than a few million years, but new species always arose to take their place – maybe asmany as 1,000 genera of dinosaur lived at some timebetween 230 million and 65 million years ago.

Dinosaur skulls lacka postfrontal bone.

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LIZARD-HIPPED Most saurischiandinosaurs had a pair ofpubic hipbones angledforward like a lizard’s, butin some these pointed back.These dinosaurs included theoften huge sauropodomorphs(four-legged herbivores), and thetheropods, mostly carnivores. Alltended to have long necks, longhands with big thumb clawsangled outward, and long secondfingers. Theropod saurischians, notornithischians, gave rise to birds.

ORNITHISCHIAN SKULLSBackward-sloping pubic bones were not unique toornithischians, but all these dinosaurs did share adistinctive lower jaw, tipped with an extra bonecalled the predentary bone. In most ornithischians,this formed the lower half of a toothless, horn-sheathed beak for cropping leafy plants. Furtherback, inside the jaws, were cheek teeth for cuttingup and chewing vegetation. In most ornithischians,these were typically leaf-shaped.

BIRD-HIPPEDAll dinosaurs belongedto one of two groups –saurischians (“lizard-hipped”),and ornithischians (“bird-hipped”). Ornithischians hadbackward-pointing pubic hipbonessimilar to a bird’s. They were all plant-eaters, and divided into three maingroups. Thyreophorans were four-footed armored and plated dinosaurs,marginocephalians had heads withbony frills or horns, and ornithopodswere two-legged herbivores.

DINOSAURS DEFINED

Gallimimus, a theropod

Predentary bone

Edmontosaurus skull

Hypsilophodon’s backward-sloping pubis had a forwardextension, the prepubis.

Hypsilophodon, an ornithischian

Hipbones of Scelidosaurus,an ornithischian

Prepubis

Astragulus (anankle bone) hasan upwardprojection.

Pubis of Plateosaurus, asaurischian

Pubis

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SAURISCHIANS CLADOGRAMTHE “LIZARD-HIPPED” DINOSAURS CALLED saurischians were one of thetwo great groups of dinosaurs. Key saurischian features include anelongated neck, a long second finger, and cavities in the bones thathoused air-filled sacs connected to the lungs. Primitive saurischianshad a pubic bone that pointed forward, as in other amniotes. This was a primitive feature inherited from the early dinosaur ancestors of saurischians. The saurischians included groups specialized for both herbivorous and carnivorous lifestyles. Saurischians survived the extinction event at the end of the Cretaceous in the form of birds.

DINOSAURS AND BIRDS

SAUROPODOMORPHS

CERATOSAURS

ALLOSAURS

GRASPING HANDAll saurischian dinosaursoriginally had a graspinghand with an opposedthumb and an elongatedsecond finger. Saurischiansfell into two main groups –the sauropodomorphs and the theropods.

THREE-TOED FOOTTheropods had three weight-bearing toes on the foot, asthe first toe did not reach theground. The middle toe – thelongest digit – bore most ofthe body’s weight. Primitivetheropods calledceratosaurs thrivedin the Triassic.

THREE-FINGERED HANDTetanurans are united bythe presence of a three-fingered hand. Primitivetetanurans includedspinosaurs, megalosaurs,and allosaurs. They werethe dominant terrestrialpredators in most Jurassicand Cretaceous ecosystems.

Dilophosaurusfrom the Jurassic

Cretaceous sauropodBrachiosaurus

Plateosaurushand

Allosaurus foot

Baryonyx hand

A number of features insauropod bodies showthat they had ancestorswith grasping hands.

First toe

Allosaurus fromthe Jurassic

SAURISCHIANSGrasping hand

TETANURANSThree-fingered hand

THEROPODSThree-toed foot

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ORNITHOMIMOSAURS

MANIRAPTORANS

RELATIVELY LONG ARMSThe coelurosaurs evolved earlyin the Jurassic, and eventuallybecame the most successfultheropods. Recent studies show that tyrannosaurs werecoelurosaurs whose forelimbshad become dramaticallyreduced in length.

HALF-MOON-SHAPEDBONE IN WRISTThis unusual wrist boneallowed maniraptorans toswivel their hands quickly,bringing fingers and clawsinto contact with prey. Thisaction probably evolved in predatory forms, but itwas retained by birds andmodified for use in flight.

Velociraptor, a kind of maniraptoran,from the Cretaceous

SAURISCHIAN EVOLUTIONThe flexible hands and air-filled bones of saurischiandinosaurs enabled them to become swift, efficient killers. Early theropods, such as the ceratosaurs, hadmore flexible bodies and tails than later saurischians.Tetanurans evolved stiffer tails, which may have helpedthem change direction when running. In coelurosaurs,key thigh muscles became attached to the hips, ratherthan to the tail, which became shorter and lighter.Feathers evolved in coelurosaurs, perhaps to keep theirowners warm. Enlarged feathers on the hands and armshelped maniraptorans control their direction as theyleapt, which may have been how bird flight originated.

Gallimimus fromthe Cretaceous

SAURISCHIANS CLADOGRAM

Ornithomimusskeleton

Deinonychushand

Half-moon-shapedbone

Maniraptorans such asthis dromaeosaur werebirdlike predators thathad flexible hands andfeet, and sharp claws.

Ornithomimosaurs likeGallimimus were long-legged coelurosaurs with large eyes.

MANIRAPTORANSHalf-moon-shaped

bone in wrist

COELUROSAURSRelatively long arms

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EARLY THEROPODSFOSSILS FROM ARGENTINA AND BRAZIL show that some of theearliest dinosaurs were two-legged, sharp-toothed, sharp-clawed saurischian (“lizard-hipped”) hunters. Three suchdinosaurs lived in South America about 228 million yearsago. Their bones show a mixture of old-fashioned andadvanced designs, but all three share features with theropods,the group all other known meat-eating dinosaurs belong to.When these creatures lived, dinosaurs seem to have beensmall and fairly uncommon creatures. Recent finds in Braziland Madagascar hinted at even earlier saurischians, though –small plant-eating prosauropods. Another very earlyherbivore was Pisanosaurus, an ornithischian (“bird-hipped”) dinosaur from Argentina.

HERRERA’S LIZARDHerrerasaurus was a large-jawed theropod thatcould grow longer than a family car and as heavyas a pony. It lived about 228 million years ago in what are now the foothills of the Andes.Herrerasaurus was one of the largest hunters of its day, only smaller than land-based relatives ofcrocodilians, such as Saurosuchus. Its likely preyincluded the rhynchosaur Scaphonyx and the smallplant-eating ornithischian dinosaur Pisanosaurus.Running on its long hind legs, it could easily haveovertaken slower-moving, four-legged prey.

FIRST SAURISCHIANEoraptor lived about 228 million years ago in Argentina. Thenear-complete skeleton was discovered in 1991, revealing thatEoraptor was only 3 ft 3 in (1 m) long, and weighed just 24 lb(11 kg). A small but fierce long-legged hunter, it had a lowersnout and shorter grasping hands than its neighborHerrerasaurus. Eoraptor would have looked somewhat like aminiature, lightly built version of later theropods, yet it hadmany more primitive features. For instance, it had morefingers, weaker claws, and fewer vertebrae supporting the hips.It probably hunted lizards and small mammal-like creatures.



Shoulder joint

HERRERA’S LIZARD

Scientific name: HerrerasaurusSize: Up to 17 ft (5 m) longDiet: MeatHabitat: Riverside woodlandWhere found: South America (Argentina)Time: Late TriassicRelated genera: Chindesaurus, Staurikosaurus

Sharpcurvedcuttingteeth

Double-hinged jawsgrippedstruggling prey.

Leaflike teeth,similar to those inprosauropods

DINOSAURS AND BIRDS

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EARLY THEROPODS

SOUTHERN CROSS LIZARDStaurikosaurus was a small, early

theropod from Brazil, namedafter the constellation of theSouthern Cross. The lightly built

two-legged hunter was around 6 ft 6in (2 m) long, but no heavier than a nine-year-old child at 66 lb (30 kg). Not all of itsskeleton is known, but like its larger relativeHerrerasaurus, Staurikosaurus had a slim,curved neck, and long, slender legs. Itprobably also had a four-fingered hand,and maybe five-toed feet – though probablyonly three toes on each foot were longenough to bear its weight.

HERRERASAURUS SKELETONThe first Herrerasaurus bones werediscovered by an Argentinian goatherd inthe 1960s, but only fragments were knownuntil 1988. Then scientists working in theValley of the Moon, a desert region in thefoothills of the Andes Mountains, found a near-complete specimen. This showedthat Herrerasaurus had sharp, saw-edgedteeth in a long, low head, with double-hinged jaws to help it get a good grip onstruggling prey. Its arms were short butthe hands were long, and its three longestfingers were tipped with strong, curved,cutting claws.

Phalanges(toe bones)

Only three fingersbore claws.

Strong clawsLong, slender toes

Bones forminghip girdle

Long weight-bearing toes

Caudalvertebrae Tibia and fibula

(lower leg bones)

Skulllightened bylarge holes

Sturdy thighs

Long head and jaws

Skin was probablyscaly.

Elongated tail tobalance front of body

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HORNS OR BUMPS ON THEIR HEADS earned some meat-eating dinosaurs the name ceratosaurs(“horned lizards”). At least 30 species are known– the largest grew 23 ft (7 m) long and weighedmore than a ton, while the smallest was nobigger than a dog. Horns were not unique to ceratosaurs, and not all ceratosaurs wereactually horned, but all shared certain skeletalfeatures. They also kept primitive features thatother theropods lost – for instance, each handhad four digits (not three). Ceratosaurs spreadworldwide and lasted nearly right through theAge of Dinosaurs. Early on, they were the mainpredatory dinosaurs, but later they seem to havepetered out in northern continents as deadliertetanuran (“stiff-tailed”) killers took their place.

HOLLOW FORMCoelophysis (“hollow form”) was a slimtheropod as long as a small car but aslight as an eight-year-old child. With a head like a stork’s, a long, curved neck, and slender legs it resembled a long-leggedbird – but unlike living birds Coelophysis had teeth, clawed hands, and a long, bony tail. One of theearliest-known ceratosaurs, it roamed Arizona and NewMexico in the Late Triassic, about 225 million years ago.Coelophysis probably snapped up lizards and small mammals,and may have hunted in packs to bring down larger prey.

DINOSAURS AND BIRDS



HORNED LIZARDS

CERATOSAURUSCeratosaurus was one of the biggest ceratosaurs,found in Late Jurassic North America and Tanzania.It had a large, deep head with a blade-like horn overits nose, two hornlets on its brows, and great curvedfangs. The arms were short but strong, with sharplyhooked claws. Ceratosaurus probably huntedornithopods such as Camptosaurus, and the sick and young of large four-legged plant-eaterssuch as Stegosaurus and Diplodocus. Thehorns might have been used forintimidation by rival males.

Elongated neck

Long,flexible tail

Primitive four-fingered hand

Reconstructed Coelophysis

Long, narrow jawswith sharp, curvedteeth

Remains of aswallowed babyCoelophysis – thisdinosaur was acannibal.

Coelophysis skeleton

Dueling Ceratosaurusmales


TWO-RIDGE LIZARDDilophosaurus (“two-ridge lizard”) was a large, lithely built ceratosaur with a pair of wafer-thin crests thatwere probably used for display.Possibly nodding his head upand down while standing side-on to a rival would havemade any male look bigger,taller, and more dangerousthan he actually was. This mighthave attracted females andscared off smaller rivals,allowing a male Dilophosaurusto win the right to mate with the females without a potentially damagingfight. Remains believedto be from Dilophosaurushave been found as far apart as Arizona and China.

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TWO-RIDGE LIZARD

Scientific name: DilophosaurusSize: 19 ft 6 in (6 m) longDiet: Meat and maybe fishHabitat: Scrub and maybe lake shoreWhere found: North America, ChinaTime: Early JurassicRelated genus: Cryolophosaurus

Long, slendertail

Long,muscularcurved neck

Paired fragile,bony crests

HORNED LIZARDS

LIGHTWEIGHT SKULLLike Coelophysis, Dilophosaurus had a kinked upper jaw witha gap between front and back teeth. However, scientistsbelieve the two were not closely related. Dilophosaurus wasmuch larger, and lived in Early Jurassic times, millions ofyears after the Late Triassic Coelophysis. Dilophosaurus’s twinridges stick up side by side from its head like two halves ofa dinner plate stood upright – they are far too delicate tohave been used as weapons.

Dilophosaurus skull

Slender teeth

Long, agile legs and feet

Silurian 443.7–416 Devonian 416–359.2 Carboniferous 359.2–299 Permian Cambrian 542–488.3 Ordovician 488.3–443.7


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IN 1985 ARGENTINIAN PALEONTOLOGISTSJosé Bonaparte and Fernando Novasnamed a large carnivorous dinosaurwith a skull unlike any discoveredbefore. They called it Abelisaurus(“Abel’s lizard”) after Roberto Abel,the museum director who discovered it.Similarities with Ceratosaurus made thescientists believe it belonged to apreviously unknown group of ceratosaurs(“horned lizards”), which they called the abelisaurids.Abelisaurids’ unusual features included a short, steepsnout with thickened bone or horns above the eyes. Soon, more members of the group came to light,including Xenotarsosaurus from South America,Majungatholus from Madagascar, Indosaurus and Indosuchus from India, and perhaps others from Europe.Most were large meat-eaters – they must have terrorizedthe plant-eating dinosaurs ofsouthern continents inCretaceous times.

HORNED HEADA victim’s view of Carnotaurusshows how its small eyes facedpartly forward, perhaps helpingto focus on its prey. Above theeyes, two short, pointed hornsstuck out sideways and upward.Scientists are unsure what the hornswere for – they are too short to kill, but perhaps they were used by males to display to females or threaten rivalmales. Perhaps a big male would bob itshead up and down to scare smaller rivalsaway, or maybe rival males stood side by side with lowered heads, butting each other in the head or neck.

Short, thickstubby horns

Lower jawslendercompared todeep head

Very short, stubbyarms and hands

Eyes see sidewaysand forward

Nostrils on short,deep snout

Teeth ratherlong anddelicateSlender

lower jaw

MEAT-EATING BULLBy far the weirdest looking abelisaurid wasCarnotaurus (“meat-eating bull”) fromLate Cretaceous Argentina. Carnotaurusgrew up to 25 ft (7.6 m) long, and had avery short, deep head with horns like abull’s. Other key features included tiny,useless-looking arms and long, slim legs.Perhaps Carnotaurus hunted by attackingyoung sauropods or medium-sizedornithopods headfirst, or scavenging fromthose it found already dead. Carnotaurusleft behind detailed fossil skin impressionsshowing that it had large, bluntly pointedscales running in rows along its back andsides. The body’s skin was also covered bya mass of disc-shaped scales – perhaps allbig theropods had scaly skins like this.

ABEL’S LIZARDS

DINOSAURS AND BIRDS



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PUZZLING JAWLINEThe lower jaw of Carnotaurus is another mystery of this unusual

theropod. In contrast to the massive head, it is slender anddelicate, and its teeth seem too lightly built to cope with

big, struggling prey. This is more evidence thatCarnotaurus might have scavenged or had

a unique hunting strategy.

MAJUNGA DOMEAnother large abelisauridwas Majungatholus, found inMadagascar. Majungatholuswas another fierce predatorwith a bony bump on itsdeep head, and it grew toover 30 ft (9 m) long. In1998, a near-completeskull was discovered on theisland where it lived.

ABEL’S LIZARDS

Very powerfulthighs

Strong shins

Tiny hallux(big toe)

Upper foot withelongated bones

High anklejoint

Rows of large, blunt scalesBody balancedabove the hips

Carnotaurus jawbones

Skull of Majungatholus

MEAT-EATING BULL

Scientific name: CarnotaurusSize: 25 ft (7.6 m) longDiet: MeatHabitat: Arid plainsWhere found: South AmericaTime: Late CretaceousRelated genera: Indosuchus, Majungatholus

Large, weight-bearing toes

WELL-CURVED VERTEBRAEEustreptospondylus was an earlytetanuran living in Englandmore than 170 million years ago. Itgrew up to 23 ft (7 m) long. Despite its size, long tail, and long, thick legs, it was lightlybuilt, with weight-saving holes in its skull, and short,three-fingered hands. This sharp-toothed theropodcould have hunted the four-legged, plant-eatingdinosaurs that shared its habitat – the platedLexovisaurus, armored Sarcolestes, and perhaps even the huge sauropod Cetiosaurus.

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STIFF TAILSMOST OF THE LATER THEROPODS are known astetanurans (“stiff tails”). The name tetanuran comesfrom a change that probably affected their legs andtails. In early theropods, muscles linked the thigh bonesto the middle of the tail, which waggled from side to sideas they walked. Tetanurans evolved shortened tail-thighmuscles, and this meant that their tails’ rear ends becameless mobile. In time some tetanurans lost their tails altogether.Tetanuran skulls were less solid than ceratosaurs’; the jaws only had teeth forward of their eyes, and each hand bore no more than three fingers. The first known tetanurans includedEustreptospondylus, Megalosaurus, and other so-called megalosaurs(“big lizards”). These medium to large theropods are mostly knownfrom scrappy fossils dating from Early Jurassic to Early Cretaceoustimes. New finds of big theropods from Asia, Africa, and Europeshow the wide variety of early tetanuran theropods.

AFRICAN HUNTERAt 30ft (9 m) long, Afrovenator (“African hunter”)was lightly built, fast-moving, and armed with 2-in (5-cm) bladelike teeth and sharp,hooked claws. It roamed a lush, hot countryside with shallow lakes and rivers. Fossil bite marks found in the ribs of a young sauropod called Jobaria suggest that sauropods were its major food supply.Afrovenator’s discovery in the Sahara desert in 1994 showed that primitive tetanurans still thrived in Early Cretaceous Africa 135 millionyears ago, 35 million years after Eustreptospondylus flourished in Europe.

Bladelike teeth2 in (5 cm) long

Three large, weight-bearing toes

DINOSAURS AND BIRDS



Tail-thigh musclebecame shortened in tetanurans.

Tetanurans haddistinctive lowerleg and anklebones.

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BIG LIZARDMegalosaurus was the first dinosaur to get

a scientific name still used today. In 1824,British scientist William Buckland described

it from a tantalizing broken piece of lower jaw.Megalosaurus probably grew longer and stronger

than Eustreptospondylus, with a large head, thickneck, short strong arms, and long powerful legs.The three main digits on each hand and foot

bore murderously long sharp claws. Yet nowhole skeleton has ever been found, and

many details are guesswork. Megalosaurus,like Eustreptospondylus, lived in the

Mid Jurassic. Fossils have beenfound in England, France,and Portugal.

STIFF TAILS

Air-filled boneslightened tetanuranskulls.

Tetanurans hadteeth only atthe front oftheir jaws.

Musculararms

Tetanurans hadthree-fingeredhands.

Large,muscular legs

BIG LIZARD

Scientific name: MegalosaurusSize: 30 ft (9 m) longDiet: MeatHabitat: Coastal woodlandWhere found: Western EuropeTime: Middle JurassicRelated genus: Eustreptospondylus

Replacementtooth Interdental

plate



MIGHTY JAWBONEThe first Megalosaurus jaw to be discoveredwas armed with great curved teeth, and musthave formed part of a long, deep head. Iteven shows where new teeth had begun togrow, replacing the old ones when they fellout, as sometimes happened whenMegalosaurus bit into its victims.

Tooth

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STRANGE SPINOSAURSWHEN A BOMB FELL ON A GERMAN MUSEUM during WorldWar II, it destroyed the best fossil remains of one of the weirdest dinosaurs of all. Spinosaurus was a big, bizarre African theropod with bonyblades up to 6 in (1.5 m) tall rising fromthe vertebrae on its back. In the 1980s,in southern England a fossil hunterchanced upon another oddity – the great curved fossil claw ofBaryonyx, a theropod with a skull like a crocodile’s. Since then,more finds of these beasts and others have shown they formed a special group of tetanuran (“stiff-tailed”) theropods, nowknown as spinosaurs. They lived in Europe, Africa, and SouthAmerica about 125–95 million years ago, when land still linkedthese continents. While all the other big predatory dinosaurs had teeth and jaws designed for biting chunks of meat fromherbivores, spinosaurs seem uniquely suited to seizing and eating large fleshy fish.



Large pollexungual (thumb claw)

Phalanges(toe bones)

Long tail

Long, narrowmandible (lower jaw)

DINOSAURS AND BIRDS

SPINE LIZARDSpinosaurus was reportedly as long asTyrannosaurus, but more lightly built.Fragments of its skull and jaw suggestit had a long, low, narrow snout, butits oddest features were the tallbony “swords” that rose from itsvertebrae. Most scientists believethese supported a tall skin sailthat could have been used fordisplay, or to help control bodytemperature. Another theory isthat the bony blades supporteda tall fleshy hump, used perhapsfor storing food. Spinosaurus fossilscome from Egypt and probablyMorocco, while a close relative,Irritator, has been found in Brazil.

HEAVY CLAWStanding on a river bank, Baryonyx might have craned its longstraight neck out over the water and grabbed unsuspecting fish in its jaws, or waded out and hooked them from the waterwith its great hooklike thumb claws, much as grizzly bears catchsalmon. We know this dinosaur ate fish because paleontologistsfound the scales of Lepidotes, a large fish, in its ribcage. Thestomach also contained some half-dissolved bones that show it had dined on a young Iguanodon. This 33-ft (10-m) Baryonyxfound in southern England was not fully grown when it died.

Long narrowsnout withspoon-shaped tip

Many extrateeth inlower jaw

Long, slim,lower jawline

Naris (nostril) setfar back

Spinosaurus at dawn

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CROCODILE MIMICSuchomimus was discovered in the Sahara Desert in 1997.Like Baryonyx, it had a long, narrow snout with a paddle-shaped tip and sharp little interlocking teeth, probably togrip slippery fish. At 36 ft (11 m) long it was not yet fullygrown. Its nostrils lay far back on its head, perhaps so it could breathe while feeding underwater or maybeinside a dinosaur’s corpse. Powerful forelimbs andthumb claws might have been used to hook yard-longfish from the water, or to tear open the tough hidesof big meaty dinosaurs that it found dead. Amazinglysimilar to Baryonyx apart from its ridged back, somescientists suspect that Suchomimus was really a large

Baryonyx after all.

STRANGE SPINOSAURS

Tiny horn on head

Low ridge onback highestabove the hips

Baryonyx skull

Modern crocodile

SUCHOMIMUS

Scientific name: SuchomimusSize: 36 ft (11 m) longDiet: Fish and maybe meatHabitat: Flood plainWhere found: North AfricaTime: Early CretaceousRelated genera: Baryonyx, Irritator, Spinosaurus

SPECIALIZED SKULLSSeen in profile alongsideeach other, the skulls ofBaryonyx and a moderncrocodile look remarkablysimilar. Both have long, low, narrow jaws, with apronounced kink in theupper one. Both jaws bristlewith sharp, slender teethdesigned to pierce and grip scaly, struggling prey.

Muscularforearm

Powerfulshoulder

Three-fingered handBig, sickle-shapedthumb claw

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GIANT KILLERSGREAT MEAT-EATING DINOSAURS were roaming the world longbefore Tyrannosaurus terrorized North America. Several may even have exceeded that monster in size. These greathunters were carnosaurs – a name once used for all largecarnivorous dinosaurs, but now used only for the allosaursand close relatives. Carnosaur heads had deep skulls withdistinctive bones and large weight-saving openings. Sometimesthey had ridges or crests on the snout or over the eyes. Their jaws were immense, with narrow, curved fangs,though weaker than Tyrannosaurus’s. Their arms were stronger,with three-fingered hands armed with sharp claws, and their greatmuscular legs with three-toed feet resembled those of a gigantic bird.Carnosaurs flourished from Late Jurassic to Late Cretaceous times, in places as far apart as North and South America, Europe, and Africa.

DIFFERENT LIZARDAllosaurus roamed western North America, East Africa, and southwest Europe in Late Jurassic times. Small adultsweighed as much as a heavy horse, while large ones grewas heavy as an elephant. Individuals of various sizesperhaps belonged to several species. Some scientistsonce thought the biggest fossils came from anothergenus altogether. Allosaurus preyed upon plant-eatingdinosaurs such as two-legged Camptosaurus and four-legged Stegosaurus and Apatosaurus. It probably hunted by ambush, hiding in trees

until a slow-moving herbivore came by.

DINOSAURS AND BIRDS



Tail probablywagged widelyfrom side to side.

Claws up to 10 in (25 cm)long seized prey.

Thigh joined to hip girdle bya femur more massive thanTyrannosaurus’s.

Tail strengthenedby sturdy vertebrae

EXPANDING JAWSTwo views of Allosaurus’s jaws show how they first gaped open (left) then moved apart (right), to bite a hugemouthful from its victim. Skull bones with movable jointsallowed this to happen. Allosaurus could also slide its skullback over its lower jaw, to let its knifelike teeth slice throughmuscle and gristle. Some scientists now think the slim lowerjaw was too fragile for fighting, and was used only for feedingafter Allosaurus had weakened its prey with axelike blows from the upper jaw, and ripped out chunks of flesh by pulling back with its powerful neck muscles.

Strongly curvednarrow claw

Forward extensionsof pubic bones madethese look like boots.

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GIANT SOUTHERN LIZARDGiganotosaurus from Late CretaceousArgentina was an immense carnivore,perhaps even longer and more massive than Tyrannosaurus. It is thought to have

been as heavy as 125 people and up to 45 feet (13.7 m) long, with a bony skull crest, deep head,

short arms, and immensely powerful legs. This big-game hunter could have attacked one of the largest-ever sauropods, Argentinosaurus, or scavenged meatfrom its corpse. Giganotosaurus flourished about

90 MYA, but, like all carnosaurs, seemingly died outbefore the end of the Cretaceous Period. In

various parts of the world they were replaced byabelisaurids or tyrannosaurids. Perhaps these

proved more efficient hunters than carnosaurs.

SHARK-TOOTHED LIZARDCarcharodontosaurus (“shark-toothed lizard”)was another huge Cretaceous “hangover:” a carnosaur theropod from mid-CretaceousNorth Africa. This dinosaur lent itsname to the carcharodontosaurids, asubgroup that also includesGiganotosaurus and another massiveSouth American theropod, perhaps thelargest of all. At nearly 46 ft (14 m) longand probably weighing at least 6.9 tons (7 tonnes), Carcharodontosaurus could havebeen as large and heavy as Giganotosaurus,although its head was shorter, and itsbrain was smaller than Tyrannosaurus’s.

Head twice aslarge as that ofAllosaurus

GIANT KILLERS

Grasping, three-fingered hand withsharp claws

GIANT SOUTHERN LIZARD

Scientific name: GiganotosaurusSize: 45 ft (13.7 m) longDiet: MeatHabitat: FloodplainWhere found: Southern South AmericaTime: Late CretaceousRelated genus: Allosaurus

Each foot supported up to 3.9 tons (4 tonnes)of body weight. Carcharodontosaurus skull

Relatively smallshoulder

Very strong,three-toed foot

Bladelike, saw-edgedteeth 8 in (20 cm) long

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ABOUT 145 MILLION YEARS AGO IN UTAH, one predator after another homedin on a feast that proved too good to be true. The scent of plant-eatingdinosaurs and the sounds of their cries led the great hunters one by oneto a pool of water where they found their prey stuck deep in mud. To an Allosaurus the sight of the giant herbivores was like an invitation tolunch. But instead of wading out into clear water, it soon found itselfsucked into something more like thick porridge. Floundering about, itmight have managed to scramble onto the back of its prey, but soon both sank and drowned. More theropods would arrive and die the sameway. Before they sank, though, many had time to bite chunks from the

herbivores and trample onthem and each other.

DINOSAURS AND BIRDS



PREDATOR TRAP

LAYING THE TRAPScientists suspect that a volcano in theyoung Rocky Mountains was responsible for forming this deadly mud trap. When the volcano erupted, it hurled out masses of ash, some of which accumulated in a localwaterhole, creating a deep mass of wet mudwith a patch of clear water in the middle.Seeing the water, thirsty plant-eatingdinosaurs ventured in to drink and weretrapped. Perhaps the mud near the edgeswas solid enough for them not to sink in, for most seem to have died in the middle.

The bleached skullof a long-drownedAllosaurus shows how the two living dinosaurs will meet their ends.

THE VICTIMSThe predator trap claimed thelives of at least 40 Allosaurus,from adults 40 ft (12 m) longand weighing 2.2 tons (2tonnes), to youngsters one-quarter their size. Allosauruswas not the only predatorydinosaur there. Othersincluded Ceratosaurus and twosmall hunters; Marshosaurusand Stokesosaurus. Amongtheir prey was the medium-sized ornithopodCamptosaurus, the plateddinosaur Stegosaurus,and the sauropodsBarosaurus andCamarasaurus.

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Pterosaurs passingoverhead ignorethe strugglinganimals below.

An Allosaurus homes in ona Stegosaurus sucked downby wet mud. Moments later,the predator too will beginto sink.

PREDATOR TRAP

DIFFERENT LIZARD

Scientific name: AllosaurusSize: 40 ft (12 m) longDiet: MeatHabitat: Open countrysideWhere found: North AmericaTime: Late JurassicRelated genus: Giganotosaurus

EVIDENCE FOR THE TRAPThe pool where the dinosaurs died is now the Cleveland-LloydDinosaur Quarry in Utah. Since 1927, when scientists began diggingfossils out of the quarry, they have found more than 10,000 bones. In any given area, big plant-eaters should normally outnumber bigpredators, yet here far more bones belonged to Allosaurus than to any of its victims. This is why scientists believe the pool was apredator trap – a deadly place where over weeks, months, and even years, a few trapped victims would lure large numbers of the creatures that preyed on them.

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HOLLOW-TAIL LIZARDSTHE JURASSIC LANDSCAPE PROBABLY TEEMED with smallpredators – the dinosaur equivalent of mammalssuch as foxes and jackals – but because their boneswere so thin and fragile very few left fossil remains.Among the best known of these are Compsognathusfrom Germany and France, and Ornitholestes from the United States. Both were probably fast runners,chasing and eating lizards, small mammals, andother creatures smaller than themselves. They wereearly members of a new tetanuran theropod group –the coelurosaurs or “hollow-tail lizards.” This greatgroup of predatory dinosaurs eventually gave rise to huge tyrannosaurs, birdlike ornithopods, and

the likely ancestors of birds.

COMPSOGNATHUS LIFESTYLECompsognathus lived on warm desert islands in what are now southern Germany and France, and was was probably the largestpredator there (small islands rarely have enough food to support large meateaters). The little dinosaur’s slender build, with a long neck, balancing tail, and birdlike legs,would have made it a fast mover. It caught and ate lizards such as Bavarisaurus among the scrubby vegetation, and perhaps also huntedthe primitive bird Archaeopteryx. Compsognathusmay also have scavenged dead king crabs andother creatures washed up on the shore.

THE LIZARD EATERThe fossil Compsognathus shown below isone of only two so far discovered. This well-preserved German specimen hadswallowed a small lizard called Bavarisaurus.Half-grown, the theropod was no biggerthan a chicken, but a French specimen was the size of a turkey. Compsognathusseemed to have just two fingers on eachhand, but scientists now know that therewere three.

DINOSAURS AND BIRDS



Fine-grained limestoneslab preserving fossil

Skin coveredwith scales ormaybe primitivefeathers

Very long,slender tail Hip

Three-toed,birdlike foot

High ankle

Tiny hallux(big toe)

Curved neck, pulledback by shrinkage afterdeath

Phalanges (fingerbones), somescattered

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ELEGANT JAW

Scientific name: CompsognathusSize: 4 ft 6 in (1.4 m) longDiet: Meat (small animals)Habitat: Desert islandsWhere found: Western EuropeTime: Late JurassicRelated genera: Aristosuchus, Sinosauropteryx

HOLLOW-TAIL LIZARDS

Elongated foot

Long, flexibleneck

Deepmandible

Large orbit

Long,whipliketail

Long manus(hand)

Nares

Orbit

Caudal vertebrae

Hip joint

BIRD ROBBEROrnitholestes, from Late Jurassic Wyoming, was much likeCompsognathus, but one and a half times as long and withlonger, more effective grasping hands. Ornitholestes mayhave hunted lizards and early birds, but it could also have tackled larger prey than little Compsognathus – for example, it may have chased and killed Othnielia, a 10-ft (3-m) bipedal, plant-eating dinosaur.

ELEGANT JAWComposgnathus (“elegant jaw”) got its name from the delicate bones inits long, low head. Its lightly built skull largely consisted of slim bonystruts with large gaps between them. The biggest openings were theorbits, or holes for the eyes. The nares or nostril holes were two smallelliptical holes near the tapering tip of the snout. Below such holes,interlocked bones formed long, slender struts that made the upperjaw. The lower jaw, too, was so shallow it looks almost fragile. Small,sharp, curved teeth were set well apart in both jaws.

Long, low head

SPECIALIZED LEGSScientists think ostrich dinosaurs such as Struthiomimus(“ostrich mimic”) and Dromiceiomimus (“emu mimic”) ran as quickly as an ostrich. All three had evolved sprinters’ legs with longer shins than thighs, and long foot and toebones. Ostriches are one of the fastest living land animals,sprinting at up to 50 mph (80 kmh). Some ornithomimidsmight have matched that. For short bursts perhaps one or two could run even faster.

BIRD MIMICThis Ornithomimus skeleton is mounted as if frozen in midstride, with neck and body tilted forward, balancedby the long tail stiffly jutting out behind. Comparingornithomimids’ bones with those of other theropodsshows that the long-limbed ostrich dinosaurs were

coelurosaurs (“hollow-tail lizards”) close tomaniraptorans, the subgroup that includes

Velociraptor and birds.


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OSTRICH DINOSAURS

Ischium

Skull with largeeye sockets and brain

Long tail with upto 40 caudalvertebrae

Extremely longfoot

DINOSAURS AND BIRDS


Long phalangeswith weakly curvedunguals (claws) Very long

metatarsalbones

ORNITHOMIMID OR “BIRD MIMIC” DINOSAURS werebuilt like flightless, long-legged birds such asostriches. Unlike most nonbird theropods,ornithomimids evolved a birdlike beak. However,unlike modern birds, they had a long, bony tailcore and arms with clawed fingers, rather thanwings. Ornithomimids lived mainly in LateCretaceous times in parts of North America, East Asia, and Europe, and probably in Africa and Australia too. Ornithomimids may haveroamed open countryside, pecking at plants and maybe sometimes snapping up smallanimals. Large eyes helped them spot prey and watch for danger. If a tyrannosaur caught an ornithomimid by surprise, it could deliver a terrible kick with its sharp toe claws, but it was more likely to sprint away from danger.

Very high anklejoint

PELICAN MIMICPelecanimimus (“pelican mimic”) was an early ornithomimidfrom Europe. It had more, but tinier, teeth than any otherknown theropod (more than 200).The sharp, close-packedteeth formed long cutting edges – in later ostrichdinosaurs teeth must have become smaller still,until in time they all disappeared. Anotherapparent oddity was a skin throat pouch likea pelican’s. Pelecanimimus was found near anancient lake, so perhaps it had waded out inshallow water to catch fish. These could havebeen stored in its pouch before it swallowedthem or took them back to a nestful of young.

CHICKEN MIMICGallimimus (“chicken mimic”),the largest known ostrichdinosaur, was three times aslong as a tall man. It had asmall, birdlike head on a long,flexible neck, a long, narrow

beak, and big eyes on the sidesof its head to spot danger from

almost any direction. Slender armsended in gangly, three-fingered hands

held with palms facing into the body.Their long, curved claws might have hooked

leafy twigs or seized small mammals and lizards.The hindlimbs had long shin and upper footbones, ending in three long toes tipped withsharp claws. A long, tapered tail stuck out stifflyto balance the head and neck. Gallimimus roameda dry region of semi-desert, where plants weremost plentiful along moist river banks.

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More than 70tiny teeth inupper jaw

Eyes at sides of head,giving a wide view

Toothless beakcovered with a horny sheath

Toes shortcompared to rest of foot

About 150 tinyteeth in lower jaw Skin throat

pouch, perhapsto store food

CHICKEN MIMIC

Scientific name: GallimimusSize: 19 ft 6 in (6 m) longDiet: Plants and perhaps animalsHabitat: River valleysWhere found: East AsiaTime: Late CretaceousRelated genera: Struthiomimus, Ornithomimus

OSTRICH DINOSAURS

Hand shorterthan in mostornithomimids

Shin longer thanthigh, designed for sprinting

Hand could haveserved as a hook.

Flexible shoulderjoint

THE TYRANNOSAURIDS OR “TYRANT LIZARDS” were the fiercest predatorsin western North America and Asia 65 million years ago. Among thelargest and most terrifying of all meat-eating dinosaurs, they firstappeared about 80 million years ago, and were among the last dinosaurs to become extinct.Surprisingly, these monstrousanimals evolved from ancestors that wereshorter and lighter than a man. Despite this, tyrannosauridsevolved to immense size – an adult Tyrannosaurus could grow longer than the width of a tennis court, as heavy as an elephant, and tall enough to look into a first-story window. Massive legs bore itsweight on three large, birdlike clawed toes. Tyrannosaurid arms wereabsurdly short, but were also strong, ending in fearsome two-clawedhands. However, their chief weapons were awesome jaws, armed withhuge fangs able to deliver a bite as powerful as an alligator’s.

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DINOSAURS AND BIRDS



Birdlike legbones mightimply theability to run.

Stable ankle forwalking on roughground

Thick teeth,almost as wideas long

Elongatedupper partof foot

THE TYRANT’S SKULLA short, deep snout helped give Tyrannosaurus’sgreat skull a boxlike shape when seen from theside. Big holes between the bones helped to reduceits weight. The immensely powerful jaws – bigenough to swallow a humanwhole – were curved, sothat as they closed, theirgreat fangs all met at once.The teeth themselves had sawlike edges at theback and front, leavingdistinctive puncture marksin the bones of prey suchas the horned dinosaurTriceratops. Eye holes and thetell-tale shape of its brain-casereveal that Tyrannosaurus had bigeyes and a well-developed sense of smell.

BONY SCAFFOLDINGCompared to most other theropods, tyrannosaurids had larger skulls,

more powerful jaws, stouter teeth, a thicker neck, a shorter body, and very tiny arms. The skull was nearly half as long as the backbone between hips and head – the thick neck must have had extremely

strong muscles to support and move its weight. Arms were typicallyno longer than a man’s, but very muscular. All this

suggests tyrannosaurids were predators designedaround their bone-crunching, flesh-shredding

mouths. Skeletons unearthed since 1990 haveincluded the largest Tyrannosaurus specimens

ever discovered. These have sparkedcontroversy about whether

tyrannosaurids showed sexualdifferences – perhaps

with females largerthan males.

Skeleton ofTyrannosaurus rex

Pairedrockerlikepubic bones

Middle metatarsalnarrows to a splint.

Each footsupported a load half as heavy as an elephant.

Immenselypowerfulthighmuscles

Ungual (bonesheathed witha horny claw)

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TYRANNOSAURIDS

KING OF THE TYRANT LIZARDS

Scientific name: Tyrannosaurus rexSize: 39 ft (12 m) longDiet: MeatHabitat: Open woodlandWhere found: North AmericaTime: Late CretaceousRelated genera: Albertosaurus, Alectrosaurus

The lower jaw’sbones showedsome flexibility.

Massive head withrigidly joined bonesfor a strong bite

ON THE HUNTTyrannosaurus rex (“king of the tyrant lizards”) walkedheavily on its great hind limbs, with head jutting forward,and a level back and tail. It probably trailed after herds ofhorned and duck-billed dinosaurs browsing through woodsand flowery, ferny glades. Tyrannosaurus rex would haveeaten large meaty dinosaurs it found already dead, but also

attacked any individual too sick, old, or young to keep up withthe rest. Some scientists believe it sprinted after prey, whileothers think it could only manage a fast walk. Tyrannosaurus rexwould have moved in for the kill with gaping jaws. Seizingsmall dinosaurs in its mouth it could have shaken them todeath. Biting a mighty mouthful of flesh from a larger victim,it could have hooked its finger claws into the creature’s hide tohold the body still. When its prey collapsed from loss of blood,Tyrannosaurus rex would use one great clawed foot to hold thecreature down, grip its neck or flank between its teeth, thenjerk its head back, tearing out colossal chunks of meat.

Thick, muscular necksupported by short,wide vertebrae

Two-fingeredhand on a smallbut sturdy armAnkle joint

with bonesforming asimple hinge.

Only the toestouched theground.

ALBERTA LIZARDAlbertosaurus, shownhere above a felledCentrosaurus, wasrelatively small bytyrannosauridstandards – though still about 26 ft (8 m) long.Some scientists think smaller tyrannosaurids could have run at speeds ofup to 25 mph (40 kph), making them formidable hunters. Alioramus, anothersmall tyrannosaurid, roamed Mongolia, which was then joined to North Americaby a land bridge. Other Asian tyrannosaurids included Alectrosaurus andTarbosaurus (which may be a species of Tyrannosaurus itself). Siamotyrannusfrom the Early Cretaceous rocks of Thailand hints that tyrannosaurid ancestors probably first arose in Asia, about 120 million years ago.

UNUSUAL CLAWSThe first digit claw onTherizinosaurus’s hand grew longer than a man’s arm, but the other two clawswere shorter. All three clawsresembled scythe blades, beinggently curved, flat-sided, and tapering to a narrow point. The claws were so long that Therizinosaurusmight have walked upon its knuckles when on all fours. Its huge claws still puzzlescientists. Compared to a dromaeosaurid’s talons,Therizinosaurus’s claws appear unsuited to aggression.If not used in courtship or for raking plants, theymight have been used to rip open termites’ nests.

HOW SCYTHE LIZARDS LIVEDTherizinosaurus seems to have been built for the kind of life led by gorillas or by large,extinct mammals such as giant ground slothsand chalicotheres. It ambled around on itslong hind limbs, sometimes propping upthe forepart of its body on its finger claws.Sitting on its haunches, supported by itstail, Therizinosaurus could have craned itslong, straight neck to crop trees with itstoothless beak and stretched its hands toclaw more leafy twigs toward its mouth.

THERIZINOSAURS (“SCYTHE LIZARDS”) were the oddest ofall known dinosaurs. For many years, scientists had to guess what they looked like from scraps of fossilsthat included four-toed feet like a prosauropod’sand scythe-shaped claws. Paleontologistsnamed the mysterious owner of the giantclaws Therizinosaurus. In 1988, morecomplete skeletons of an earlier relative,Alxasaurus, turned up in China. Comparisonof this therizinosaur’s bones with previousfinds enabled scientists to picture “scythe lizards” as large, slow-moving, bipedal creatures. The biggest resembled bizarre,extinct, hoofed mammals called chalicotheres. Therizinosaurs’wrist and toe bones show they were “stiff-tailed” theropodsrelated to Oviraptor. Therizinosaurs lived in East Asia andNorth America. Most kinds lived in Cretaceous times, but a therizinosaur has been reported from the Early Jurassic.

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SCYTHE LIZARDS



The first digit’sclaw tended tobe the longest.

Small headsupported bya long neck

Therizinosaurclaw fossil

Socket wherethe claw joinedits finger bone

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SCYTHE LIZARDS



SCYTHE LIZARD

Scientific name: TherizinosaurusSize: 39 ft (12 m) longDiet: Probably plantsHabitat: Wooded riversidesWhere found: East AsiaTime: Late CretaceousRelated genera: Erlikosaurus, Nanshiungosaurus

Three stampedingBeipiaosaurus alarmsmall birds andfeathered dinosaurs.

Broad bodycontaining a largedigestive system

BEIPIAO LIZARDBeipiaosaurus was named after Beipiao, the Chinese city nearto where its fossils were discovered in 1996. As long as a tallman, but more heavily built, Beipiaosaurus lived more than120 million years ago, long before the largest “scythelizards.” It was also less highly evolved. Its body had a sizablehead with lower tooth crowns, hands longer than thighs,three-toed feet, and long shins. The most exciting discoverywas that fine feathery filaments had covered its arms, legs,and maybe the rest of its body. This find strengthened theevidence that many theropods were not scaly, but covered in long down that resembled an emu’s hairlike feathers.

Short, broad,four-toed foot

Three elongatedfinger claws

Skeletal reconstruction of Therizinosaurus

Hips werebroader than intypical theropods.

SCYTHE LIZARDTherizinosaurus was one of the last and most awkwardly built of all therizinosaurs. Paleontologists Dale and DonaldRussell reinvented Therizinosaurus’s appearance by matching

its incomplete bones with the known bones of othertherizinosaurs. They borrowed its small head from

Erlikosaurus, based its lower jaw’s length on Segnosaurus, and made its jaws

toothless. Its long neck, back,and broad hips were based

on Nanshiungosaurus.

Bonessupporting the fairly straight neck



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DINOSAURS AND BIRDS

CRETACEOUS CONFLICTRearing in intimidating poses, a group oftherizinosaurs confronts a hungry Tarbosaurus in the riverside forests of Cretaceous Asia.Therizinosaurus’s claws were unsuitable for tearingflesh, despite their great length, so it may haveused its large size to frighten attackers. Although itwas the smaller dinosaur, Tarbosaurus could mounta vicious attack. The tyrannosaur preyed uponother dinosaurs, as well as therizinosaurs.

Triassic 251–199.6 299–251 Paleogene 65.5–23 Neogene 23–present


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SCYTHE LIZARDS

Cretaceous 145.5–65.5Jurassic 199.6–145.5


Silurian 443.7–416 Devonian 416–359.2

OVIRAPTOR (“EGG THIEF”) was a long-leggedtheropod with large eyes, a toothless beak,and a bony tail. Oviraptor and its closerelatives seem to have been the dinosaursmost closely related to birds. The scientistwho described Oviraptor in 1924 believed he had found one that was killed whilestealing the eggs of the horned plant-eaterProtoceratops. He named his find Oviraptorphiloceratops (“egg thief, fond of horneddinosaurs”). In the 1990s, however, moreoviraptorid dinosaurs were found with similareggs. In one of these eggs lay the tiny bonesof an oviraptorid embryo. Far from stealingother dinosaurs’ eggs, the adults had diedprotecting their own, in the way ground-nesting birds do today. Oviraptor livedabout 80 million years ago in what is nowthe Gobi Desert of Mongolia and China.

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Carboniferous 359.2–299 Permian Cambrian 542–488.3 Ordovician 488.3–443.7

EGG THIEVES

DINOSAURS AND BIRDS


Hard-shelled eggs,like a bird’s

DEVOTED MOTHERSThis lifelike model shows an Oviraptor mothersettling down to brood her clutch of eggs. The nest isa sandy mound with a hollow scooped out in the middle.Inside, she has laid in a circle more than 18 long eggs.Crouching low, the big, birdlike creature uses her own bodyheat to keep her eggs warm at night. By day, the soft, downyfeathers that cover her body and arms shield her eggs fromthe Sun’s fierce heat, and from sand blown about by strongwinds. If another dinosaur tries to steal her eggs, she mightscratch it with her sharp finger claws or, like an ostrich,deliver a terrible kick.

EMBRYOTiny bones still cradled by fragments of eggshellreveal the remains of an oviraptorid embryo inan egg laid 80 million years ago. The unhatcheddinosaur lay curled up in an egg no more than 3 in (7 cm) across. Had it hatched, the babywould have grown to be 6 ft 6 in (2 m) long. Finds of dinosaur embryos are rare because their bones were often too fragile to be preserved.

Oviraptoridembryo in egg

DESERT DISASTERFossil bones and eggs show

where an oviraptorid diedguarding a nest of 22

long eggs, laid in acircle. This nest layon sandy ground,probably at the edgeof a desert oasis. To

protect the eggs from a rare desert downpour,

the parent had seeminglyspread its clawed arms over the

nest as a bird might spread itswings. Suddenly, a rain-drenched

dune slid down over the nest, andburied the dinosaur and its eggsbeneath a sandy avalanche.

Fossils of anoviraptorid nesting with eggs


Paleogene 65.5–23

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Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Neogene 23–present


EGG THIEF

Scientific name: OviraptorSize: 6 ft 6 in (2 m) longDiet: UncertainHabitat: Semi-desertWhere found: Central AsiaTime: Late CretaceousRelated genera: Conchoraptor, Ingenia

EGG THIEVES

Tall, bony crest coveredwith a horny sheath

Toothlessbeak

Neckmuscles

Tail

Finger

Dorsal vertebra

Claw Foot

LIGHTWEIGHT SKELETONA reconstructed oviraptoridskeleton reveals the slenderscaffolding of hollow bones inside the creature’s body. Oviraptorids had long arms and extremely long,grasping, three-fingered hands, which were armed withsharp, strongly curved claws. The elongated shins andfeet enabled them to run fast, and the tail was relativelyshorter than that of most other theropods. Altogetheroviraptorid dinosaurs resembled big, flightless birds.They even used the same muscle as birds – the ilio-tibialmuscle – to pull their legs backward. However, certaintelltale details, such as forward-pointing hip bones and

a backward-pointing hallux (first toe), indicate thatthese theropods were not in fact birds.

BIZARRE HEADSAn oviraptorid head was more like a bird’shead than that of a typical theropod dinosaur.The jaws formed a deep, toothless beak, andthe lightweight skull largely consisted ofstrong, bony struts that were light and thin.The skull contained huge holes for the eyes. A crest covered in horn ran along the top ofan oviraptorid dinosaur’s nasal area. Feathers

might have covered the rest of thehead, which here appears bare

and scaly.

Hallux(first toe)

Ilio-tibial muscle

Pubicbone

Shin

Fluffy downinsulated the body.


UNUSUAL BODYCaudipteryx had a short head and a beak with sharp, buckteeth in the front upper jaw. From its lightly built bodysprouted shorter arms than those of most advancedtheropods, although there were long, three-fingered hands that ended in short claws. Long legs and birdlike toes indicate that this dinosaur was a fast runner. Caudipteryx’sbony tail was among the shortest of all known dinosaurs, andmost of the animal was covered in some type of feathering.

OF ALL CHINA’S AMAZING NON-BIRDdinosaurs and birds, none has provenmore astonishing than Caudipteryx (“tailfeather”). This long-legged, turkey-sizedcreature seems a mixture of both kinds ofanimal, with a birdlike beak, feathers, andshort tail, but teeth and bones that proclaimit a non-bird theropod dinosaur. Caudipteryxlived in Early Cretaceous times, not long afterthe first known bird. Scientists have suggestedit might have been either a strange theropoddinosaur, a theropod dinosaur with ancestorsthat flew, or a bird that evolved from birdsthat had lost the power to fly. It is mostprobable that Caudipteryx was a maniraptoran(“grasping hand”) dinosaur and that the birdlikeoviraptorids were its nearest relatives.

FEATHER FUNCTIONFeathers of different kinds covered most of Caudipteryx. Short down providedinsulation, and implied that Caudipteryxwas warm-blooded. Feathers with 8-in

(20-cm) long quill shafts sprouted from itsarms, fingers, and tail, but Caudipteryx couldnot fly. Its wing feathers were symmetrical,whereas the wing feathers found in

birds that can fly are asymmetrical.Caudipteryx’s feathers might havebeen brightly colored andused for mating display.

Caudipteryx hadwing feathers thatwere symmetricalin shape, like thiswild turkey feather.

TAIL FEATHER

Wing feather

Down feather

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DINOSAURS AND BIRDS


PUZZLING RELATIONSHIPSScientists stressing Caudipteryx’sbirdlike nature have claimed it had a reversed “big” toe,

and used muscles like a bird’s to pull back its legs

as it walked. Other scientistsbelieve both suppositions areunproved, and stress detailsindicating that this was a non-bird dinosaur. Forinstance, the pubic hip

bones pointed forward,while the beak, tail bones,and other hip bones hintthat Caudipteryx wasclosely related to thedinosaur Oviraptor.

TAIL FEATHER

Scientific name: CaudipteryxSize: 2 ft 4 in (70 cm) tallDiet: Plants and possibly animalsHabitat: WoodlandWhere found: East AsiaTime: Early CretaceousRelated genus: Possibly Oviraptor

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TAIL FEATHER

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Neogene 23–present


Cretaceous 145.5–65.5 Paleogene 65.5–23


DEINONYCHUS (“TERRIBLE CLAW”) and other dromaeosaurids (“running lizards”)were small, aggressive,hunting dinosaurs. Fewtheropods matched theirintelligence, and nonebrandished such aterrifying combinationof weapons. The jaws ofdromaeosaurids bristled with big,curved, bladelike fangs, their three-fingeredhands bore hooked claws, and curved clawssprouted from their long, birdlike toes. Thehuge switchblade claws on their second toeswere twice as long as any of their otherclaws. Dromaeosaurids ranged fromabout 6 ft 6 in (2 m) to 20 ft (6 m) inlength. They first appeared duringthe Jurassic period, although most knownfossils date from Cretaceous times. While thenorthern and southern continents were stilllinked, dromaeosaurids spread widelythrough them.

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TERRIBLE CLAWMounted as if leaping in for the

kill, this Deinonychus skeleton showssome of the key anatomical features

that made dromaeosaurids so feared. Its jaws gape to bare wicked-looking rows

of fangs. The gangly arms unfold like a bird’swings and stretch out to hook their curvedclaws into a victim’s scaly hide. The switchbladetoe claws could rise, ready to flick forward anddisembowel prey. Bony rods sprouted forwardfrom the tail bones to overlap the bones in front and form a bundle that stiffened the tail. The leaping dinosaur would swing its tail around to help it keep its balance. The tail acted as a flexible rod, darting in all directions as the dinosaur moved.

Skull deeper and morestrongly built than thatof Velociraptor.

One of a number of skeletons ofDeinonychus found inMontana and Wyoming.

CAMOUFLAGENo one knows for sure whether all dromaeosauridshad scaly or feathered skin. If some had scaly skinsthese could have been tinted or patterned in waysthat made their bodies blend in with theirsurroundings. If Deinonychus wasscaly, as shown here, stripes orspots on its skin would havehelped to conceal it in thedappled light beneaththe trees. Itscamouflage wouldhave made it lessvisible to its prey.

TERRIBLE CLAWS

Striped Deinonychus

Large claw swungdown to deliverslashing attacks.

Skin is striped likethat of a living tiger.

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Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Paleogene 65.5–23 Neogene 23–present


TERRIBLE CLAWS

FEATHERED VELOCIRAPTORVelociraptor (“quick robber”), a dromaeosaurid the length of a tall man, appears below as a model covered with feathers, not scales. Fine, hair-like strandsprotect its body from heat and cold, and long, showyfeathers sprout from its head and arms. Since 1996,fossil feathers like these have turned up in China with superbly preserved small theropods including the dromaeosaurids Sinornithosaurus (“Chinese birdlizard”) and Microraptor (“tiny robber”). Working withChinese scientists in 2001, Mark Norell of the American Museum of Natural History revealed yetmore evidence that all such theropods closely related tobirds had feathers not scales.Further proof came in 2007when Norell and twocolleagues disclosedtheir discovery of aVelociraptor armbone that hadquill knobs for anchoring feathers.

Tail stiffened bybony struts exceptat its base, justbehind the hips.

TERRIBLE CLAW

Scientific name: DeinonychusSize: 10 ft (3 m)Diet: MeatHabitat: Open woodlandWhere found: North AmericaTime: Early CretaceousRelated genera: Dromaeosaurus, Velociraptor

Velociraptor had tokeep its great

second-toe clawraised when it walked.

Each hand had three,long, narrow fingerswith sharp claws.

ThisVelociraptor’ssharp claws andagility failed tosave its life.

Cretaceous 145.5–65.5

Hairlike featheryfilaments probablyinsulated the body.

DUEL TO THE DEATHTwo tangled fossils found in the Mongoliandesert were a Velociraptor and a Protoceratopsthat died while fighting. This scene shows thateven an aggressive theropod ran risks when itfought a well-defended plant-eater. The lithehunter Velociraptor had grasped the plant-eater’ssnout while delivering kicks to its throat. TheProtoceratops had gripped its attacker’s arm in its strong beak. Suddenly, sand loosened from adune by wind or rain smothered both of them.

Troodon might have hadvertical pupils thathelped it hunt at night.

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DINOSAURS AND BIRDS



CRETACEOUS LANDS TEEMED WITH small, hunting dinosaursdesigned, like prehistoric roadrunners (swift, ground-dwellingbirds), for dashing around and seizing small, backboned animals.Many of these small-game hunters belonged to the maniraptoran(“seizing hands”) dinosaurs – the theropod group to which birdsbelong. Their long, clawed hands stretched out to seize prey, thenpulled in and back, much as a bird’s wings flap. Like birds, somemaniraptorans had feathers. Traces of feathering survive in thewell-preserved fossils ofCaudipteryx (“tail feather”)and Sinornithosaurus(“Chinese bird lizard”)from China. Feathersor down very likelyalso covered theNorth AmericantheropodsBambiraptor and Troodon.

ROAD RUNNERS

Gastralia(belly ribs)

Head of Troodon

Troodontids’ hip bone shapesare partly guesswork, but the pubic bones juttedforward, not back, as in more birdlike theropods.

Long, slenderarms bearingthree-fingeredhands with sharplycurved claws

Small, raised“switchblade”second toe claw

Close-fittingmetatarsal bones

Flattened chevrons,stiffening the tail

Ischium

Long, slim tibia

SMART DINOSAURWith a large brain for the size of its body, Troodon wasone of the most intelligentdinosaurs. Troodon’s eyescould focus on objectsdirectly in front of it, whichhelped Troodon to judge whena victim came within range.Troodon may well have huntedat dusk, as its big eyes verylikely saw clearly in dim light.

WOUNDING TOOTHNamed for its curved, saw-edged teeth,Troodon was a big-brained, long-leggedhunter that was the length of a tall human. It flourished in western North Americaabout 70 million years ago. Like Velociraptor,Troodon was built on slim, birdlike lines, andhad a switchbladelike second toe claw that itheld clear of the ground as it walked. UnlikeVelociraptor, however, Troodon’s big toe clawwas too small to allow it to tackle largegame. Troodon might have killed babydinosaurs, but its main prey were birds,lizards, snakes, and small mammals.

BAMBIRAPTOR IN ACTIONBambiraptor was an agile hunter ofsmall game. Stepping watchfullythrough the undergrowth, it wasready to leap into action if afrog jumped or a mammalmoved. The theropodstrode rapidly after itsintended victim. Ifits prey suddenlydarted away, Bambiraptor followedswiftly, keeping its balance byshifting its stiffened tail from sideto side. The hunter probablyended most chases by grabbingits prey in its hands anddelivering a fatal bite.

TROODON SKELETONArms outstretched, as if running to attack a victim,this mounted skeleton gives a good idea of Troodonas an active, agile hunter. The maniraptoran’slong, low skull housed a brain as big as an emu’s,and its jaws bore about 120 of the small, sharp,cutting teeth that earned this troodontid dinosaurits name. This theropod’s basket of gastralia, or“belly ribs,” perhaps acted in a similar way to adiaphragm, which helps the lungs to work.

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ROAD RUNNERS

Slashing kicks from the longclaw on each foot coulddisembowel larger prey.

BAMBI RAIDERDiscovered in 1994 in

Montana, the 75-million-year-old skeleton of Bambiraptor is one

of the most complete and birdlike ofany non-avian North American dinosaur.The 3-ft 3-in (1-m) long individual was notyet fully grown. An agile runner, with shinslong like a bird’s, Bambiraptor had large eye sockets, and a bigger brain for the size of its body than any other known dinosaur. Some of its bones contained air sacs linked to the lungs, as in a bird. They supplied extra oxygen for a creature that was likely very active. Bambiraptor was probably warm-blooded, with downy feathering thathelped to conserve body heat.

A rather deep snoutand large teeth wereamong Bambiraptor’sleast birdlike features.

Its wishbone andshoulders helped it to swing its longarms out to grab.

A wrist joint like abird’s allowed it tofold its hands as abird folds its wings.

Forward-facing eyes

Half-moon-shapedwrist bones madepossible a grabbingaction, like the flightstroke of a bird.

WOUNDING TOOTH

Scientific name: TroodonSize: 6 ft 6 in (2 m) longDiet: MeatHabitat: Open woodlandWhere found: North AmericaTime: Late CretaceousRelated genera: Byronosaurus, Saurornithoides

Bambiraptor skeleton

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BIRDS CLADOGRAM

DINOSAURS AND BIRDS

CONFUCIUSORNITHIDS

ENANTIORNITHINES

SHORTENED TAIL A tail with less than 25vertebrae sets birds apartfrom other maniraptorans.This feature reflects a needto lighten the skeleton. Thelong tail of Archaeopteryxwould have made it quite a clumsy flier.

PYGOSTYLEBirds more advanced than

Archaeopteryx have their lastfive tail vertebrae furtherreduced and fused into aplate of bone called thepygostyle. These birds include confuciusornithidsand the Ornithothoraces.

ALULAOrnithothoracines are unitedby the alula – a feather thathelps direct air over the upper surface of the mainwing. Enantiornithines were a Cretaceous radiation of the Ornithothoraces.

Iberomesornis, from EarlyCretaceous Spain, wasthe earliest member ofthe Ornithothoraces.

Alula

Pygostyle

Tail

Skeleton of EarlyCretaceous bird

Heron wing

Confuciusornis was a jay-sized bird fromEarly Cretaceous China.

ORNITHOTHORACESAlula

Pygostyle

AVESShortened tail

SEVERAL FEATURES ALLOW BIRDS TO BE distinguished from their closestrelatives, the dromaeosaurid dinosaurs, but Archaeopteryx – the “firstbird” – now seems less birdlike than people once thought. Skeletaldetails such as a reduced tail and distinctive feet set birds apart fromother animals. Although all birds possess feathers, these are not aunique feature of birds, as feathers are also present in non-aviantheropod dinosaurs, such as Caudipteryx. Birds more advanced thanArchaeopteryx originated around the Jurassic-Cretaceous boundary. Their tail, hand, and chest bones were much like those of modern birds.

ARCHAEOPTERYX

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PATAGOPTERYX

HESPERORNITHIFORMS

ICHTHYORNITHIFORMS

MODERN BIRDS

FULLY FUSED FOOTIn the ornithurines andPatagopteryx, the elongatefoot bones called themetatarsals are completelyfused to form a structurecalled the tarsometatarsus.These bones were notcompletely fused togetherin earlier birds.

PRONG ON QUADRATEThe Ornithurae aredistinguished by thepresence of a sharp prongon their quadrate bone,which points toward the tip of the snout. They alsopossess distinctive hips and a shortened back that hasfewer than 11 vertebrae.

ROUNDED HEAD OF HUMERUSCarinate birds are well-adapted for powerful flight.The rounded head on thehumerus gives carinates a wider range of motion at the shoulder joint and, therefore, a morepowerful flapping action.

SADDLE-SHAPED FACESNeornithines have saddle-shaped articulating faces ontheir neck vertebrae. Theyalso lack teeth and have anextra crest on the humerus.These modern birds arosein the Cretaceous and havebecome the most diversegroup of birds.

Ichthyornis fromthe Cretaceous

Sparrow

BIRD EVOLUTIONWhether flight in birds originated from running or climbingdinosaurs remains the subject of argument. Primitive birdspossess features associated with flight, but some may have lived on the ground. Trends such as the loss of serrations onthe teeth and the shortening of the tail reflect a move toward a lighter skeleton and more agile flying abilities. The evolution of the alula allowed birds to become even better fliers. Laterbirds evolved stronger wing and chest bones, and more flexiblenecks. Teeth were retained in birds until the Neornithes.

BIRDS CLADOGRAM

Fused metatarsal bones

Patagopteryx, aflightless, runningbird from CretaceousSouth America

Prong

Humerus (upperarm bone)

Roundedhead

Saddle-shapedface

Hesperornisskull

Hesperornis neck vertebra

NEORNITHESSaddle-shaped faces to

neck vertebrae

CARINATAERounded head

of humerus

ORNITHURAEProng on quadrate

Fully fused footskeleton

Hesperornis fromthe Cretaceous

ARCHAEOPTERYXRECONSTRUCTEDArchaeopteryx’s skeleton hints at keyfeatures inherited from increasinglyadvanced types of theropods. Betweenthem these gave the first bird a mobilehead, sharp curved teeth, a long, slim neck, shortened body, and a stiffened tail. Other similarities included hollowbones, long, folding arms,three weight-bearing toesper foot, and long,grasping three-fingeredhands with swivelingwrists. Even thewishbone and featherswere inherited from nonbird theropodancestors. In dinosaur terms, Archaeopteryxappears to be a maniraptoran related to dromaeosaurids, a group of theropodsthat included Velociraptor.

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ARCHAEOPTERYXTHE OLDEST KNOWN BIRD is Archaeopteryx (“ancient wing”).About 150 million years ago, this crow-sized creaturewalked and fluttered on tropical desert islands, now partof southwest Germany. Feathers sprouted from its armsand hands, its tail was long and feathered, and its big toespointed backward, much like a perching bird’s. Yet thecreature’s sharp teeth, clawed hands, bony tail core, and many other features resemble a small carnivorousdinosaur’s. Indeed two of the 10 fossils foundbetween 1855 and 2004 were at first misidentified asCompsognathus, which shared the same islands. The number of similarities between smalltheropods and Archaeopteryx convince mostpaleontologists that birds are simply akind of dinosaur that learned to fly.

FEATHER PRESERVATIONFine-grained Bavarian limestone preservesthe delicate feather impressions of thisArchaeopteryx. Feathers probably evolved in theropods from fuzzy down that helpedkeep the body warm, and the first longfeathers may have been for show. ButArchaeopteryx’s primary feathers were madefor flight – each had a shaft closer to oneedge than the other, as in flying birds today.Only such asymmetrical feathers are capableof flight. Long legs would have helped thebird to leap off the ground, and arms andwrists were adapted for flapping.

DINOSAURS AND BIRDS



Each long flightfeather had anasymmetrical shaft.

Half-moon-shapedwrist bone fanning thehand for flight stroke

Abdominalribs as inreptiles but notin modern birds

Slender snout hadsmall, sharp teethcurving back.

Horn-tipped clawson front of wings

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TREES DOWNOR GROUND UP?

Perched on a branch, thisreconstruction of Archaeopteryx

shows one way in which earlybirds might have taken to the

air. Some scientists suppose it usedits claws to climb up trees, then

fluttered weakly back to the ground.Yet the desert islands where Archaeopteryx

lived had no tall trees. Instead, perhaps itran after flying insects, leaped to catch

them in mid air, then stayed aloft byflapping its wings. The downstroke

movement probably evolved fromthe way its ancestors stretched out

their hands to grab at prey, buttook on a new role when

coupled with feathers.Fluttering down or leaping in the air, Archaeopteryxcould not have flown far or fast – its breastbone wastoo small to anchor strongflight muscles.

STRANGE CLAWSThe young of a strange South American bird,called the hoatzin, are born with claws on theleading edge of each wing, much like those of Archaeopteryx. If a snake scares them out of their nest, they leap out and fall to the ground,then claw their way back up the tree using theirfingers, toes, and beak. Some scientists believeArchaeopteryx used the horny tips of its fingers in a similar way, slowly hauling itself up trees until it gained enough height to launch itself. Hoatzinsmay be among the most primitive modern birds,with no close living relatives, but they are still farmore advanced than Archaeopteryx.

ANCIENT WING

Scientific name: ArchaeopteryxSize: 2 ft (60 cm) longDiet: Small animalsHabitat: Tropical desert islandsWhere found: Western EuropeTime: Late JurassicRelated genus: Perhaps Rahonavis



Horny clawshelped to graspbranches.

Tail feathershelped the birdkeep its balanceduring flight.

Feathers sproutedfrom a bony tailcore like that ofmost dinosaurs.

Tail core of 23 bones– fewer than in almost all nonflying dinosaurs –reduced the bird’s weight.

Fully reversedhallux (big toe),as in all birds

ARCHAEOPTERYX

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EARLY BIRDSFOR MORE THAN A CENTURY afterthe discovery of Archaeopteryx, no oneknew how such bony tailed, toothy, claw-fingered, weak-winged “bird dinosaurs”evolved into today’s beaked, toothless,effortless flyers. Since 1990, though, new findsof early fossil birds from Spain, China, andelsewhere have helped solve this puzzle. Thefirst of these birds lived in Early Cretaceoustimes, millions of years after Late JurassicArchaeopteryx. Cretaceous birds show step-by-step changes that transformed the firstclumsy flappers into masters of the air. Yetamong these new fossil finds are strange birdsthat branched off, forming once-successful linesthat petered out, leaving no descendants,including the extremely varied enantiornithines(“opposite birds”). Both of these groups diedout in the Late Cretaceous, about 5 millionyears before the Age of Dinosaurs ended.

EARLY SEABIRDSHesperornis was an enormous, long-neckedseabird up to 6 ft (1.8 m) long, which huntedfish in the shallow seas covering Late CretaceousKansas. It had a big head and long beak armed withsmall, pointed teeth. Unlike many other seabirds of the time, Hesperornis had lost the ability to fly, and itsforelimbs had shrunk until only a pointed humerusbone remained. Seabirds like this evolved from earlierfliers to become powerful swimmers and deadly fish-hunters. Their large back feet were probably webbedfor propulsion, and the stubs of their wings could have been used for steering.

CRETACEOUS BIRD RELATIVESLate Cretaceous alvarezsaurids, such as Shuvuuia, werelong-legged, feathered, flightless, and had tiny teeth intheir beaks. Their ridged breastbones seem designed toanchor flight muscles, and their wrist and hand bones

are fused together, as if to form a strong support for flight feathers. These features at first led to

them being identified as a group of primitiveflightless birds, but they have now been

reclassified as close relatives of realbirds. Their forelimbs were absurdly

short and each ended in a singlemassive finger with a powerfulclaw. Some scientists suggest that they used their claws toopen termite nests and feast

upon the grubs inside.

DINOSAURS AND BIRDS

CONFUCIUS BIRD

Scientific name: ConfuciusornisSize: Up to 24 in (60 cm) longDiet: Probably plantsHabitat: Lakeside forestWhere found: East AsiaTime: Early CretaceousRelated genus: Changchengornis



Two long, showytail featherspresent onpresumed males.

Splintlike bonesbore tiny wingsincapable of flight.

Long, sharp,narrow beak,with little teeth

Legs set far backmade walking difficult.

Cervical vertebraesupporting verylong neck

Elongated body withlong, narrow hip bones

143

CONFUCIUS BIRDConfuciusornis was a magpie-sized bird that lived in EarlyCretaceous China, more than 120 million years ago. It perched in trees, ate plants, and bred in colonies of hundreds. Some of the birds (probably the males) had long tail feathers, possibly for display, while others(probably females) were smaller with much stubbier tails.Confuciusornis flew more strongly than Archaeopteryx, butshowed a strange mixture of advancedand old-fashioned features. Its clawedfingers, flattish breastbone, wrists,hips, and legs remind scientists ofArchaeopteryx. Newer featuresincluded its deeper chest, strut-shaped coracoid (a shoulderbone), horny, toothless beak,and a pygostyle – a shortenedtail core of fused bones. Some scientists put Confuciusornisin a group of birds called the Pygostylia.

EARLY BIRDS

Triassic 251–199.6299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Paleogene 65.5–23 Neogene 23–present


Toothless beakcovered by ahorny sheath

Deepened breastbone anchoringstrong flightmuscles

Tail feathers grewfrom fused tailbones.

Presumed femaleshad a short tail

Three fingers withcurved clawsprojecting fromeach wing

Hallux (big toe)reversed as inliving birds

Flight featherswell designed forpowered flight

Thumb supportingfeathers used inslow flight

Eoalulavis fossil inultraviolet light

DAWN LITTLE-WING BIRDDescribed in 1996, sparrow-sized Eoalulavis from Early CretaceousSpain is the earliest known bird to have a tuft of feathers sproutingfrom its thumb. Projecting from its main wing’s leading edge, thistiny wing or “alula” kept Eoalulavis airborne at low speeds, helpingit to land and perch on trees. The alula was an importantinnovation, found in birds today. Eoalulavis belonged to theOrnithothoraces ("bird chests"), stronger and more maneuverableflyers than Confuciusornis and its kin. Yet Eoalulavis was on a sidebranch from the line of evolution that led to modern birds, and might not even have been warm-blooded.

144


NEW BIRDSALTHOUGH THE REPTILES that we think of as dinosaurs died out 65 million years ago, their probable descendants – birds – survived.Throughout the Cenozoic they evolved,diversifying into different species suited for life in almost all parts of the world. Today, birds flourish – their 9,000 or so living speciesoutnumber mammal species nearly two to one. But countless Cenozoic bird species did not survive to the present day. Most are stillunknown, but all the Cenozoic fossil birds so far discovered belong to the same great group as present day birds – the Neornithes or “newbirds.” Their hallmarks are a toothless, hornybeak, fused limb bones, and an efficient, four-chambered heart to aid rapid muscle movementin flying. Extinct neornithines, however,included flightless giants, strange waterbirds,and also land birds unlike any still around.

FLIGHTLESS GIANTSSubfossil bones like this moa foot have yielded

molecules revealing relationships between giant flightlessbirds extinct for up to 1500 years. In 2001 scientists provedthat New Zealand’s moas, birds up to 11 ft (3.5 m) tall, andMadagascar’s mighty elephant birds shared ancestors withthe still-living South American rhea, African ostrich, andAustralian emu. Such so-called ratites must have spreadthrough the southern continents before they were separatedby sea about 70 million years ago. Ratites represent the Paleognathae (“old jaws”) – a less advanced type of neornithine than the Neognathae (“new jaws”), to which almost all other living birds belong.

FLYING GIANTDiscovered in 1979, Argentavis magnificens(“magnificent Argentine bird”) was probably the largest bird that ever flew. It had an enormous 25 ft (7.6 m) wingspan,greater than was once thought possible for a flying bird, andmay have weighed as much as a jaguar. This vast bird was ateratorn – a gigantic relative of the turkey vultures seen in the Americas today. Like these, it possibly had a bare head and neck for burrowing deep into a corpse without messingup its feathers. Although huge, the feet of these birds wereextremely weak, so they would not have been capable of liftingprey from the ground. Instead, they probably soared abovegrassy pampas, swooping down on grazing flightless birds and mammals to kill them on the ground, or feeding from corpses of those that had already died.



Argentavis – wingspan25 ft (7.6 m)

Preserved Moa foot

Claw

Andean condor –wingspan 11 ft(3.2 m)

SkinBone

DINOSAURS AND BIRDS

Early illustration of a moa and kiwis

TERROR CRANEThe huge carnivorous Titanis (“giant”)was a phorusrhacid or “terror crane” – one of a group of flightless birds that rivaled mammals as top predators in SouthAmerica for millions of years. Standing 8 ft(2.5 m) tall, with a big head, powerful hookedbeak, and long legs with powerful talons,Titanis was among the last phorusrhacids,and crossed the Panama Isthmus intoNorth America when the continentsjoined around 3 million years ago. It probably hunted on open plains,seizing prey with wings that had re-evolved digits tipped with hugeclaws, before holding it down withits feet and tearing out chunks offlesh with its beak. Titanis’s armsare unique – earlier phorusrhacidshad stubby, useless wings.

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NEW BIRDS

Clawed fingerscapable ofseizing prey

Broad, flat beaklike a duck’s

Long, curved,slender neck

Long legs likea shorebird’s

Long toes to preventsinking in soft mud

Presbyornisskeleton

PUZZLING PRESBYORNISPresbyornis was a weird waterbirdwith a ducklike head and beak,certain skull features like aflamingo, and some limbbones like a shorebird.Despite this confusingmixture of ingredients, mostscientists group it with theducks, geese, and swans. Itprobably waded in shallow, saltylakes and fed much like a flamingo,by filtering algae from the water.Presbyornis fossils are foundworldwide, and this long-lived genusmay have first appeared in the age ofthe dinosaurs. However, it is best knownfrom North American fossils of around

50 million years ago, some in large nesting colonies.

Titanis mayhave had anornamentalcrest

Headsupported ona long neck

Lower mandiblemuch smallerthan upper

Sharp toeclaws couldinflict severewounds.

Three-toedfoot capableof giving aknockout kick

Scientific name: TitanisSize: 2.5 m (8 ft)Diet: MeatHabitat: GrasslandWhere found: North AmericaTime: Neogene (Pliocene)Related species: Ameginornis, Phorusrhacos

GIANT

Beak with strong,sharp, hookedupper mandible



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DINOSAURS AND BIRDS

TITANISFour million years ago on a Central American plain,the primitive horse Hipparion flees from the suddenappearance of the area’s most formidable predatorout of nearby pampas grass. As Hipparion bolts, the 8-ft (2.5-m) Titanis turns in pursuit, arms outstretchedwith two vicious claws ready to seize the hapless littlehorse. Despite weighing more than 330 lb (150 kg),Titanis is surprisingly agile, with powerful legs capableof bringing down even the fastest prey. When Northand South America link up, and North Americanwildlife floods south, Titanis will be the only majorpredator to make the journey in the oppositedirection, surviving until perhaps 400,000 years ago.



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NEW BIRDS


148

INTRODUCING SAUROPODOMORPHSTHE LIZARD-HIPPED OR SAURISCHIAN DINOSAURS were divided into two great groups – theropods, which gave rise to birds, and sauropodomorphs (“lizard-foot forms”).Sauropodomorphs had small heads, teeth shaped forcropping plants, long necks, and roomy bodies fordigesting large amounts of low-quality leafy foods. Mostpossessed large thumb claws, evolved from small bipedalancestors. By Late Triassic times there were already twotypes of sauropodomorph: prosauropods (“before thelizard feet”) and sauropods (“lizard feet”). Prosauropodsranged from small two-legged forms to great four-leggedbeasts. Sauropods were immense herbivores propped up bypillarlike limbs, with stubby feet and hands much like thoseof an elephant. They included the largest, heaviest animalsthat ever lived on land. Both groups spread around theworld – prosauropods perhaps evolved first, but diedout in Middle Jurassic times. Sauropods persisted almost right through the Age of Dinosaurs.

PROSAUROPODSScientists have disagreed aboutexactly which anatomical“ingredients” set prosauropods apart from sauropods. A list of keyprosauropod features drawn up in1990 included small, “saw-edged,”leaf-shaped teeth, a skull half as longas the thigh bone, and jaws hingedbelow the level of the upper teeth.They also had broad pubic hip bonesforming a kind of apron, large,pointed thumb claws, and traces oftiny fifth toes on the feet. Somescientists believe prosauropodscould also have had a hornybeak and fleshy cheeks.

DINOSAURS AND BIRDS



Tail has about 50caudal vertebrae.

All sauropods had at least44 caudal vertebrae

Small, saw-edged,leaf-shapedfront teeth

Narrow trackmade by asauropod’serect limbs

Fossilizedsauropodfootprint leftin soft ground

This famousreconstruction showsApatosaurus’s taildragging on theground. In fact, it was probably carried horizontally.

Large strong,curved thumbclaw

Broad footwith fourlong toes

Paired pubicbones project like an apron.

HOW SAUROPODS WALKEDScientists used to think that the heaviestsauropods must have lived in lakes andswamps, buoyed up by water. Finds of fossil footprints have disproved this oldidea. They also show quite narrow tracks,proving that sauropods walked with limbserect beneath their bodies, like cows orelephants, not sprawling to either side like the limbs of lizards and turtles.

Thick bones,supportingpillarlike limbs

Sternal platesform a heart-shaped shield.

Lufengosaurusskeleton

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DID SAUROPODS REAR?Prosauropods could certainlyreach to nip at high leaves, butcould the immense sauropodsalso stand on hind legs? Inthis model for a museumdisplay, a Barosaurus rears toprotect her young one from a marauding Allosaurus,preparing to stamp down on the predator or lash at itwith her tail. However, somescientists still doubt whethersauropods could havepumped the blood sohigh to their brains, or whether mothers took care of theiryoung like this.

INTRODUCING SAUROPODOMORPHS

DECEPTIVE LIZARD

Scientific name: ApatosaurusSize: 69 ft (21 m) longDiet: PlantsHabitat: FloodplainWhere found: North AmericaTime: Late JurassicRelated species: Barosaurus, Diplodocus



At least 12 cervicalvertebrae reinforcingthe long neck

Eleven or fewerdorsal vertebrae

Nostril openings farback on the skull

KEY SAUROPOD FEATURESApatosaurus (“deceptive lizard”) was a diplodocid, or double-beam,sauropod, also known as Brontosaurus (“thunder lizard”). Thediplodocids are named after the dual extensions on the chevronsof their tail vertebrae, but they also display distinctive featuresseen in other sauropods. Many of these affect the dinosaur’soverall shape. Sauropods “borrowed” back vertebrae to extendtheir necks, resulting in at least 12 neck bones, but just 11 orfewer back vertebrae. These bones’ neural spines weretypically V-shaped, to cradle a strong ligament that helped to

raise the weight of the neck and head. The columnlike limbswere also adapted to bear huge weight – ankles were cushioned by

springy cartilage; and they had a full set of five fingers on each hand,but the number of bones in each digit was reduced. Sauropods walkedon their toes with palms raised, and a fleshy pad supporting most ofthe weight. Their thumbs and three toes bore large claws. Sauropodteeth also show tell-tale wear marks made by biting off leaves, andtheir skulls have large nostril openings far back on the head.

An Allosaurusthreatens a youngBarosaurus.

Large thumband toe claws

Broad, short,stubby foot bones

Adult Barosaurus mighthave raised its head up to 50 ft (15 m).

Young Barosaurusshelters behind its mother.

Ordovician 488.3–443.7 Silurian 443.7–416

150

PROSAUROPODSTHE PROSAUROPODS (“BEFORE SAUROPODS”) thrivedbetween about 230 and 178 million years ago. They wereamong the first plant-eating dinosaurs, and the first landanimals tall enough to browse on trees. Various groupsevolved, with species ranging from creatures lighter thana man and walking on their hindlimbs to ponderousfour-legged giants – the first dinosaurs to grow as heavyas an elephant. However, they all shared certain keyfeatures, including a small head, long neck, heavy body,long tail, and huge, curved thumb claws. Their size andadaptations for feeding on available vegetation made theprosauropods hugely successful – they probably lived allover the world, and came to outnumber all other largeland animals. Eventually, though, they were replaced by their possible descendants, the even more huge and specialized sauropods.

LONG THUMB CLAWPlateosaurus’s forelimbs hadfive digits of varying lengths –two short outer fingers, twomuch longer middle fingers,and a huge curving thumb.This claw was so long that itwould have got in the waywhile walking on all fours, andprobably had to be held off theground. It would have made a formidable defensive weapon

for jabbing at attacking theropods.With the rest of the hand, this claw

could also have grasped tree trunks for support or pull down branches as

Plateosaurus reared to nibble the leaves.

MOUSE LIZARDProsauropod nests have been found, proving thatsome young hatched from surprisingly tiny eggs,often no larger than a small songbird’s. However,even such sparrow-sized hatchlings could eventuallygrow into adults weighing about 260 lb (120 kg).This discovery was made in Argentina, wherepaleontologists unearthed the nest, eggshells,and five little hatchlings of a prosauropodthey called Mussaurus (“mouselizard”), which may in fact bebabies of a previouslydescribed species.

Jaws containedmany small, flat-sided teeth.

Teeth snipped offleafy twigs with apowerful bite.

Long, sharp, bonycore of the thumbclaw

Plateosaurus hand

Mussaurus hatchling

DINOSAURS AND BIRDS

Seconddigit’s long,curved claw

Devonian 416–359.2 Carboniferous 359.2–299 Permian Cambrian 542–488.3


Horny sheathcovering thumb claw

Thumb claw heldclear of the groundwhen walking


151

FLAT LIZARDPlateosaurus, (“flat lizard”), one of the best-knownprosauropods, was found widely in Western Europe. It grew up to 26 ft (8 m) long, with strong arms andhands. People used to think that these helped tosupport a share of its weight, and that Plateosaurusstood and ambled along on all fours. But, in 2007, itwas discovered that its palms could not face down,meaning that Plateosaurus had walked on two legs,balanced by its long, strong tail. By rising and craningits elongated neck, it could crop tree leaves beyondthe reach of other animals. Plateosaurus’s small skullwas equipped with saw-edged, leaf-shaped teeth forchopping up these leafy foods and a low jaw jointdesigned to give a powerful bite. The teeth were set inslightly from the jaw rim. The flexible neck led to along ribcage containing a long gut to process bulkyplant food, with the help of swallowed stones to grindit to a pulp.

BUS-LENGTHBEASTRiojasaurus wasone of the largestprosauropods, and one of the first truly large dinosaurs.A heavy quadruped that could grow up to 36 ft (11 m)long, one calculation puts its weight as great as 5 tons(4.5 tonnes). As prosauropods grew larger, the greatweight of intestines in front of their forward-sloping hip bones helped to make them front-heavy, eventuallyforcing them to spend their whole life on all fours.

FLAT LIZARD

Scientific name: PlateosaurusSize: 20–26 ft (6–8 m) longDiet: PlantsHabitat: FloodplainsWhere found: Western EuropeTime: Late TriassicRelated genera: Coloradisaurus, Sellosaurus

PROSAUROPODS

Toe claws wereshort but strong.

Sturdy toes boremost of the weight.

The tail taperedtoward the end.



Large gut probablyfilled with bulkyplant food

Hollows in spinalbones cut downtheir weight.

Limb bones were solidand heavy.

Long tail, deepnear its base

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SAUROPODS (“LIZARD FEET”), THE LARGEST DINOSAURS of all, probablyevolved from ancestors no bigger than a dog, yet some very earlysauropods were already sizeable. Isanosaurus (“Isan lizard”) fromthe Late Triassic of northeast Thailand, around 220 million yearsold, had thigh bones nearly twice as long as human thighs.Another early sauropod, Vulcanodon (“volcano tooth”) from EarlyJurassic Zimbabwe, measured 20 ft (6.5 m), as long as a largecrocodile. Other early sauropods included India’s Barapasaurus(“big leg lizard”), Europe’s Cetiosaurus (“whale lizard”), andChina’s Shunosaurus (“Shuo lizard”). At up to 60 ft (18 m) fromsnout to tail, the biggest of these Early to Mid Jurassic dinosaursmatched the length of a large sperm whale. Between them,finds of fossil bones and footprints indicate that sauropodshad spread worldwide by the beginning ofthe Jurassic Period.

WHALE LIZARDCetiosaurus was a Mid Jurassic sauropod firstdiscovered in England in the early 1800s. In 1841 it became the first sauropod to get a scientificname. Paleontologist Richard Owen, who namedit, knew this was a giant reptile, but its fossilvertebrae were huge and spongy, somewhat like a whale’s. Owen thought the creature might have swum in the sea. Later finds revealed thatCetiosaurus had been a land animal up to 60 ft(18 m) long, and as heavy as several elephants.This rather primitive sauropod’s weight waslargely in its heavy limbs and vertebrae.

STIFF-NECKED CETIOSAURUSMost reconstructions have pictured Cetiosaurus as a swan-necked treetop browser. In fact the dinosaur’s stiffneck stuck straight out, counterbalanced by a raised tail,and Cetiosaurus could not raise its head much higher thanits shoulders. However, it could lower its head to drink, orswing it in an arc 10 ft (3 m) across to crop fern fronds orsmall, leafy trees. This sauropod roamed low-lying shoresof an ancient sea that covered much of England.

DINOSAURS AND BIRDS

Devonian 416–359.2 Permian Cambrian 542–488.3 Ordovician 488.3–443.7 Silurian 443.7–416


Only pale bones in thisreconstructionare real – otherswere invented.

The neck bones’design made themrather inflexible.

EARLY SAUROPODS

This model skull is guesswork– no Cetiosaurus skull isknown with certainty.

Carboniferous 359.2–299

Some tail bone chevronsare shaped like those ofthe later Diplodocus.

Pubic bonesprobably helped tosupport the large,heavy gut.

Relatively short anddeep tail, shown heretrailing on the ground,but probably carriedoff the ground in life

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SHUO LIZARDShunosaurus from Middle Jurassic China grew about

33 ft (10 m) long. Early sauropods like this already showthe basic characteristics of small head, long neck and tail,

deep body, and pillarlike legs, but these were not yet fullydeveloped. Their necks and tails were relatively short, fewervertebrae had fused to their hip bones to help support thebody, and their spinal bones were not yet deeply scooped out to reduce weight. Shunosaurus had only 12 neck bones,13 back vertebrae, 4 vertebrae fused with its hip bones, and

44 bones in its tail. Later, larger sauropods had many morevertebrae – for instance, Apatosaurus had nearly twice

as many tail bones. Finds of many Shunosaurus fossils,some almost complete, make this among the best-

known of the sauropods. Some skeletons show that the last tail bones were fused together and

swollen to form a club. Like an ankylosauriddinosaur, Shunosaurus could have swung its tail as a formidable defensive weapon.

CHANGING VERTEBRAEA rather solid, heavy Cetiosaurus spinal bone (above right)contrasts with a Brachiosaurus dorsal vertebra (above left).Brachiosaurus was a later, more advanced, type of sauropod.In Brachiosaurus, any bone not needed in the centrum hasbeen lost, but the neural spine and zygapophyses are longand strong. In more advanced sauropods, bone growthwas concentrated along the lines of greatest stress, like the steel tubes of scaffolding.

EARLY SAUROPODS

SHUO LIZARD

Scientific name: ShunosaurusSize: 33 ft (10 m) longDiet: PlantsHabitat: FloodplainWhere found: East AsiaTime: Middle JurassicRelated genera: Datousaurus



Centra

Neck relativelyshort for asauropod

Zygapophyses

Neuralspines

Shoulder blade –two fused bones,the scapula andcoracoid Skull, one of the few

kinds of sauropodskulls to survive

Large footwith long,deep claws

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DOUBLE BEAMS

DOUBLE BEAMDiplodocus grew longer thana tennis court, yet weighed nomore than two large elephants. Most of itslength came from its slender neck and tail, anddeep hollows in the spinal bones reduced theirweight. New calculations suggest that this hugecreature could not lift its long, stiff neck muchhigher than its shoulders. Instead of browsing onhigh leafy twigs, as most people imagine, it wouldhave grazed low-growing ferns. Standing in a fernmeadow, Diplodocus could have swung its neckfrom side to side, stripping the fronds with itspeg-shaped teeth. Swallowed stones may then havehelped to mash the fronds up inside its stomach.

HEAVY LIZARD

DINOSAURS AND BIRDS



Barosaurus’scenter of gravitywas near its hips.

Front limbs wereshort compared to the hindlimbs.

Ten tall dorsal vertebraeformed the spinal boneson the back.

At least 80 caudalvertebrae made up the tail’s core.

Chevrons

Thirty rodlike bonesformed the tail’s“whiplash” end.

THE DIPLODOCIDS (“DOUBLE BEAMS”) were immense four-legged sauropods. They had small heads shaped much like a horse’s, and peg-shaped teeth only at the front of the jaws. Their front limbs seem ridiculously short, but all four legs were built like an elephant’s in order to support the heavy body. An incredibly long neck was balanced by an even longer tail that tapered to aslender “whiplash.” Diplodocids get their name from twin extensions called chevrons in the bones of theirmiddle tail. These “double beams” may have protected the blood vessels in their tails if they pressed down onthe ground for the animals to rear. Similar chevrons arefound in some other sauropods, perhaps close relatives.Almost all diplodocids lived in the Late Jurassic. Thebest known, such as Apatosaurus, Diplodocus, andSeismosaurus, are from the western United States.

The straight, slimfemur was shapedlike a stove pipe.

Bones just likeDiplodocus’ssupported the limbs.

Scientific name: BarosaurusSize: 89 ft (27 m) longDiet: PlantsHabitat: FloodplainWhere found: North AmericaTime: Late JurassicRelated genera: Apatosaurus, Diplodocus

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DECEPTIVELIZARDApatosaurus grewnearly as long asDiplodocus, butbecame farheavier – as heavyas four or fiveelephants. Much ofits weight lay in itsthick heavy bones, and it is equallywell known as Brontosaurus (“thunder lizard”) for its supposedstomping walk. In fact, fossil bones named Brontosaurus turnedout to match those from the already named Apatosaurus.Another error involved the creature’s head, which was notdiscovered for many years. People mistakenly believedApatosaurus had had a box-shaped skull like Camarasaurus’s,but when a real Apatosaurus skull was finally unearthed, it waslong and low, with peg-shaped teeth, like Diplodocus’s.

Very long bones inthe neck

The flexible tailmay have crackedlike a whip.



EARTH-SHAKING LIZARDSeismosaurus (“earth-shaking

lizard”), from New Mexico, hasbeen called the longest dinosaur

of all, probably measuring around110 ft (34 m) and weighing up to

33 tons (30 tonnes). The LateJurassic rocks that this monstercame from have yielded other

North American diplodocidgiants. Amphicoelias and

Supersaurus may have beeneven longer and heavier

than Seismosaurus. Theskeletons of all three

genera are veryincomplete, though, and

two or more kinds ofdiplodocid may eventually

prove to be just one.Recent discoveries suggestthat even larger sauropods

may have evolved inCretaceous South America.

“Stretched” bonessupported theneck.

Comparativelytiny head

HEAVY LIZARDAt up to 89 ft (27 m) long, Barosaurus had a strong resemblance to Diplodocus, but with one important difference. One third of thiscreature’s length was made up by its amazingly long neck. Barosaurushad the same number of neck vertebrae as Diplodocus (fifteen), but each was remarkably stretched to create an astounding reach.Strangely, while diplodocid necks were longer than those of othersauropods, their forelimbs were shorter. If these giants grazed onlyon all fours, this would have limited their reach, but if they couldrear on their hindlegs, then reduced weight in the front of the bodywould have been an advantage. Barosaurus is therefore one of thebest arguments for this kind of behavior – at full stretch, a rearingBarosaurus could hold its head 49 ft (15 m) above the ground.

Tail containeddiplodocid-typevertebrae.

DOUBLE BEAMS

BONY SCAFFOLDINGScientists know more about thisdinosaur’s skeleton than almost anyother sauropod’s, thanks to its manyfossil remains. Camarasaurus had a highskull that was short from front to back. Itsvertebrae included 12 short neck bones with long,straight ribs that overlapped those behind to stiffen the neck. There were also 12 back bones, fivesacral vertebrae fused to the hip bones,and 53 tail bones. The weight-bearing bones of eachlimb ended instubby digits.

CAMARASAURUS (“CHAMBERED LIZARD”) gets its name fromthe roomy hollows in its backbone that helped to limitthe weight of this sturdy creature. Camarasaurus lived inLate Jurassic western North America. Fossil hunters inColorado, Wyoming, and Utah have found the remainsof individuals ranging from babies to adults. The tiniestfossil belonged to an embryo 3 ft 3 in (1 m) long that was almost ready to hatch from an egg smaller thansome birds’ eggs. This was the first sauropod embryo ever discovered. Outside North America, close relatives of Camarasaurus appear to have lived in whatare now Portugal and Spain. Less closely related sauropods thatreputedly share similar featureswith Camarasaurus lived as far away as Mongolia,China, and Thailand.

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Massive hindlimbs, withclawed toes supportedby a fleshy pad.

Moderately short,but sturdy tail

DINOSAURS AND BIRDS



CHAMBERED LIZARDS

Barrel-shapedribcage

Deeply hollowedvertebrae in back

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LIFESTYLECamarasaurus adults probably fed below shoulder height, swinging theirstrong necks stiffly sideways and down to strip tough leaves from shrubbytrees with their teeth. Young camarasaurids seem to have eaten plants withsofter leaves. Signs of wear on the teeth of adult camarasaurids hold cluesto this sauropod’s diet. They hint that an adult Camarasaurus ate moreabrasive plants than sauropods such as Diplodocus. This would havemeant that both types of sauropod could have lived in thesame place at the same time without competing forfood. Perhaps camarasaurid young shared thediplodocids’ diet because they could not yet digest tough leaves.

Forelimbs endingin short, stubbytoes with sharpthumb claws

CHAMBERED LIZARDS

Short, blunt, deephead, with eyes andnostrils far back

CHAMBERED LIZARD

Scientific name: CamarasaurusSize: 59 ft (18 m) longDiet: PlantsHabitat: FloodplainWhere found: North AmericaTime: Late JurassicRelated genera: Possibly Aragosaurus

Antorbital fenestra (“window infront of the orbit”) – an air-filledhole in the skull found in mostdinosaurs and other archosaurs

Shoulders perhaps higherthan most sauropods’

BOXY SKULLCamarasaurus’s short, deep skullhad a muzzle that was blunt

like a bulldog’s. Its orbits, or eyesockets, lay far back in the head,

where the tiny braincase was also located. The nares – two holes for

the nostrils – were set high up in front of the eyes. Only slim, bony struts separated these sockets and holes, but the

jaw bones provided solid supports for the deeply rooted, spoon-shaped teeth that ran

around Camarasaurus’s mouth. Below eachorbit, muscles that worked the jaws bulged from

a skull hole called an infratemporal fenestra, or “window below the temporal bone.”

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LONG, PILLARLIKE FORELIMBS earned Brachiosaurus (“arm lizard”)its name and gave it a back that sloped steeply down to itshindquarters. This high-shouldered sauropod was built like a mighty giraffe. With a long neck much like the boom of a crane, Brachiosaurus could lift or lower its head to browse

on tree leaves or fern fronds. This giant plant-eater’s fossilscrop up in the Late Jurassic rocks of western North America,

southern Europe, and east Africa. Similar sauropods have been said to include Cedarosaurus, Dystylosaurus, and Sauroposeidon. There

are more supposed brachiosaurids (“arm lizards”) but some seem tohave been more closely related to Brachiosaurus than others. Many

sauropods are known from so few bones that comparing theirrelationships is often difficult.

A DINOSAURIAN GIRAFFEPowerful muscles might have raisedBrachiosaurus’s head 43 ft (13 m) high,making it more than twice as tall as a giraffeand high enough to peer over a four-storybuilding. Brachiosaurus was not the longestof dinosaurs, but it was probably among the heaviest. One expert estimated that itweighed 76 tons (78 tonnes) – as much as13 African bull elephants – although othershave put its weight lower, at 31–46 tons(32–47 tonnes). Certainly, the hollowsin its vertebrae and the air spaces in its ribs helped to lighten someof its bones. However, its thick-walled limb bones wereimmensely heavy.

DINOSAURS AND BIRDS

ARM LIZARDS

Shaft – long middlesection – of femur(thigh bone)

Devonian 416–359.2 Carboniferous 359.2–299 Permian Ordovician 488.3–443.7 Silurian 443.7–416


Cambrian 542–488.3

PILLARLIKE LIMBSAs long as a very tall man and massivelythick, the Brachiosaurus femur (thigh

bone) was one of the largest, strongest,and most solid of the bones in its body. Brachiosaurus’s upper arm bones were even longer than its thigh bones – unusual for a sauropod. The scientist whodescribed Brachiosaurus initiallymistook one of its upper arm bones for a femur.

INTERNAL ANATOMYA scaffolding-like bony frame supported Brachiosaurus’sbody. Its skeletal parts included a high-domed skull, 13neck bones, 11 or 12 dorsal vertebrae, and five vertebraejoined to its hips. The limbs ended in short, stubbyhands and feet, which were much like an elephant’s.Pumping blood to Brachiosaurus’s brain was a huge,but not impossible, problem. A strong heartforced out blood at high pressure, and valvesprevented the blood from falling back downthe long neck. The arteries that carriedblood to the brain were probably thickand springy, to prevent them frombursting under thestrong blood flow.

Deeply hollowedneck vertebra

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HIGH-DOMED SKULLBrachiosaurus’s oddly shaped skull had a tall, curved, bony strut that

separated the nostrils, which openedhigh and far back on its head. Thenostrils’ lofty position enabled this

sauropod to breathe while it ate,without getting leaves in its nostrils.

Brachiosaurus’s muzzle was long and low, and the strongly

built jaws were rimmed with large, spoon-shaped

teeth. Brachiosaurus bit offmouthfuls of vegetation,which it then swallowed

whole, perhaps to be mashed up by stones

in its gizzard – a chamber in its digestive system – and

chemically broken down by bacteriain its intestines. Behind the orbitsthat contained its eyes lay a small

braincase. A tiny brain was enoughto work this huge eating machine.

ARM LIZARDS

ARM LIZARD

Scientific name: BrachiosaurusSize: 82 ft (25 m)Diet: PlantsHabitat: Open woodlandWhere found: Africa, Europe, AmericaTime: Late JurassicRelated genus: Cedarosaurus

Neck muscles

Femur

Dorsal vertebra

Triassic 251–199.6 299–251 Neogene 23–present

CENOZOIC 65.5 MYA–presentMESOZOIC 251–65.5 MYA

Internal anatomy of Brachiosaurus

Shoulder blade

Some studies hint thatBrachiosaurus might

not have been able toraise its neck straight up.

Nasal opening

Orbit

Braincase

Heart

Ulna and radiusin forearm

Relatively short, thicktail carried far off the ground

Paleogene 65.5–23Cretaceous 145.5–65.5Jurassic 199.6–145.5

Gizzard

Strong, spoon-shapedteeth for cropping leaves

Devonian 416–359.2 Carboniferous 359.2–299 PermianCambrian 542–488.3 Ordovician 488.3–443.7 Silurian 443.7–416


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GIGANTIC LIZARDSHUGE BONES EARNED TITANOSAURS (“gigantic lizards”) a nameborrowed from the Titans – giants in ancient Greek mythology. In the 1990s, paleontologists described colossal bones from a titanosaurcalled Argentinosaurus, which some scientists believe was the largestdinosaur of all. Despite their name, many titanosaurs were smallsauropods – some measured less than 40 ft (12 m) long. Theirdistinctive neck, back, and tail bones led palaeontologists to decidethat titanosaurs were different from the rest of the sauropods. TheLate Cretaceous was a time in which the titanosaurs flourished. Morethan 30 kinds of titanosaur were found in places as far apart asEurope, Africa, Asia, India, and North America, but the mostsignificant titanosaur fossil finds have come from South America.

SALTA LIZARDFirst discovered in Argentina’s Salta Province,Saltasaurus was a fairly small titanosaur. It had stockylimbs, a whiplash tail, and bony studs set in the skin ofits back and sides. Other features included a singlebony spine that rose from each neck vertebra,an extra vertebra in the hip girdle, and tailbones with ball-and-socket joints. Like mostsauropods, Saltasaurus probably ate low-growing ferns and maybe browsedon tree leaves out of reach ofsmaller herbivores withshorter necks.

The muscular tail withinterlocking bonesmight have helpedprop up Saltasaurus’sbody if it reared.

“Garden rake” teethfeature in thistitanosaur’sBrachiosaurus-like jaws.

DINOSAURS AND BIRDS

Bony scutes formed part of the tough armor that plated Saltasaurus’s back.

Saltasaurus may havereared on its hind limbs to feed on high vegetation.

MISSING HEADSFor many decades, fossil hunters dug uptitanosaur bones without ever discovering askull, so no one knew what a titanosaur headlooked like. Finds of peg-shaped teeth, like thoseof Diplodocus, suggested that the head was lowand resembled that of a diplodocid. In 1996,however, the paleontologist Rubén Martínezstumbled upon a complete titanosaurskull. It had nostrils placed highabove the eyes, and a long, lowmuzzle with jaws rimmedby long teeth.

Triassic 251–199.6299–251 Paleogene 65.5–23 Neogene 23–present


161

BONY BACKSFor years, paleontologistsbelieved that the bony lumpsdiscovered with titanosaurfossils came from armoredornithischians. The 1980description of a Saltasaurus’sfossilized skin proved thattitanosaur sauropods also hadarmor. Saltasaurus had twotypes of armor. Close-packed,pea-sized lumps toughened itsskin, while scattered, fist-sized,bony plates guarded its sides.

GIGANTIC LIZARDS

SALTA LIZARD

Scientific name: SaltasaurusSize: 40 ft (12 m) longDiet: PlantsHabitat: LowlandsWhere found: South AmericaTime: Late CretaceousRelated genera: Argentinosaurus, Neuquensaurus

Titanosaur skull

DISCOVERING EGGSIn 1998, paleontologists described dramatic finds of sauropod fossil eggs. At Auca Mahuevo, westernArgentina, scientists found thousands of crushed,round eggs – as big as an ostrich’s – scattered across a vast nesting ground. Besidescontaining tiny bones, some eggsalso held bits of fossilized scalyskin. Pencil-shaped teeth provedthat the eggs’ embryos weresauropods. They were probablytitanosaurs – the onlysauropods to live in Argentina in theLate Cretaceous.

Cluster ofsauropod eggs

Scientist excavating eggsat Auca Mahuevo

Saltasaurus’s headresembled that ofBrachiosaurus.

Bony neck tendonssuggest that Saltasauruscould not lift its head muchabove shoulder height.

Jurassic 199.6–145.5 Cretaceous 145.5–65.5




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DINOSAURS AND BIRDS

JURASSIC BROWSERSmall herds of brachiosaurids roamed riversideforests of conifers, cycads, and ferns that grew in the warm, Late Jurassic climate. Brachiosaurusstood at the edge of woods, swinging its long neckto reach the leaves of tall trees. Lowering its neck,the massive creature grazed on fronds of low-growing ferns. A dinosaur as large as this needed a lot of plant food to survive, so Brachiosaurusprobably spent most of its time eating.



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BRACHIOSAURIDS



In stegosaurs such asStegosaurus, the armorplates were arranged intwo rows along themidline of the body.

All ornithischians descendedfrom long-legged, bipedalancestors, such asHeterodontosaurus.

The predentary boneis a single U-shapedbone that is coveredin life by a horny beak.

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ORNITHISCHIANS CLADOGRAMTHE “BIRD-HIPPED” DINOSAURS called ornithischians include thearmored stegosaurs, the horned ceratopsians, and the duck-billedhadrosaurs. All ornithischians share key features of the jaws and teeth that allowed them to crop and chew plants efficiently. Advancedornithischians, especially the hadrosaurs, became highly modified for chewing plants. They evolved hundreds of self-sharpening teethand special skull hinges that helped them grind their teeth together.All ornithischians probably evolved from a bipedal ancestor similar to Heterodontosaurus, one of the most primitive ornithischians.

DINOSAURS AND BIRDS

HETERODONTOSAURUS

THYREOPHORANS

PREDENTARY BONEGrooves on the predentarybone’s hind margins allowedthe two dentary bones in thelower jaw to rotate slightly.This let ornithischians rotatetheir tooth rows and therebychew their food.

INSET TOOTH ROWThe Genasauria are united byhaving chewing teeth that areset in from the side of theface. Heterodontosaurus showedthis feature and yet seemsprimitive in other ways.Perhaps all ornithischians hadan inset tooth row.

ROW OF SCUTESThyreophorans had armorplates in rows along theirbodies. Early thyreophoranswere fast, partially bipedaldinosaurs, but advancedforms had short feet andwere slow-moving animalsthat relied on body armorfor defense.

Skull and jaws of Cretaceousornithischian Ouranosaurus Inset tooth rows

Skull and jaws of Jurassicornithopod Heterodontosaurus

Scute

Cretaceous ankylosaurEdmontonia

ORNITHISCHIAPredentary bone

GENASAURIATooth row inset

from jaw margins

Row of scutes on body

The rostral bone grew at the tip of the upper jaw andformed a powerful beak.

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ORNITHOPODS

PACHYCEPHALOSAURS

CERATOPSIANS

ASYMMETRICAL ENAMELCerapods had a thicker layerof enamel on the inside oftheir lower teeth. The teethwore unevenly with chewingand developed sharp ridgesthat allowed cerapods tobreak down tougher plantfood than other dinosaurs.

SHELF ON BACK OF SKULLA bony shelf that jutted outfrom the back of the skull is the key characteristic thatunites the marginocephalians.It only developed when theanimals became sexuallymature, and may have evolved for use in display.

ROSTRAL BONECeratopsians – the hornedmarginocephalians – are unitedby the presence of the rostralbone. This toothless structureformed an enlarged cutting areaon the beak. Early ceratopsianswere about 3 ft 3 in (1 m) long,but Late Cretaceous forms wereas big as the largest elephants.

Triceratops

ORNITHISCHIAN EVOLUTIONDespite descending from similar ancestors, the differentornithischian groups evolved distinct modes of life. Thyreophoranswalked on all fours, while ornithopods diversified as small, bipedal(two-legged)runners. Large, partly quadrupedal ornithopods withwidened beaks evolved late in the Jurassic. Marginocephalians datefrom the Mid Jurassic. Pachycephalosaurs and primitive ceratopsiansremained bipedal, while the advanced Cretaceous ceratopsianswalked on all fours.

ORNITHISCHIANS CLADOGRAM

Thick enamellayer

Bone of lower jaw

Unerupted tooth

Section through hadrosaur jaw

Iguanodon and otheradvanced ornithopodswere large and may havewalked on all fours.

Stegoceras belonged to agroup of pachycephalosaursthat had thick, rounded skulldomes, which were probablyused in display and combat.

Skull and jaws of Cretaceousceratopsian Triceratops

CERAPODAAsymmetrical enamel

on cheek teeth

MARGINOCEPHALIAShelf on back of skull

Rostral bone

Bony shelf

Stegoceras skull

Inside of thelower jaw

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SMALL BIPEDAL PLANT EATERSDURING THE JURASSIC PERIOD, several types of two-legged ornithischian (“bird-hipped”) dinosaurs evolved. Early kinds were no bigger than a dog, but latersome grew to lengths of 30 ft (9 m). They walked on hindlimbs much longerthan their arms and had horny beaks and ridged teeth for crushing leafy plantfood. Scientists, unsure how some of the small early forms were related to oneanother, grouped most kindstogether as ornithopods, or“bird-footed” ornithischians.Their hind feet resembledthose of a bird, with threelarge, forward-pointingtoes tipped with claws orblunt nails. Without daggerlike teeth or talons to defend themselves, mostornithopods ran away from danger and some were among the fastest of all dinosaurs.

LESOTHO LIZARDThe dog-sized early plant eater Lesothosaurus, which lived inLesotho and South Africa in Early Jurassic times, is too primitiveto be classified with the true ornithopods. Its jaws moved only upand down, not side to side, so it is likely to have fed by slicingrather than grinding leaves. With long sprinter’s shins, the animalcould race away from its enemies at high speeds. At other times,Lesothosaurus would have gone down on all fours to eat low-growing plants, raising its head frequently to watch out forsneaky predators.

DINOSAURS AND BIRDS



HIGH RIDGE BROWSERHypsilophodon (“high ridge tooth”) was named for its grooved, high-ridged cheek teeth, which made it very efficient atchewing tough Cretaceous vegetation. Its jaws hinged belowthe level of the teeth, giving it a strong bite, and as its upperjaws moved out, the lower jaws moved in, with the result thatupper and lower teeth constantly sharpened one another.

This 5 ft (1.5 m) long animal lived inNorth America and Western Europe.

Short arms with stubby fingers

Feet as long as the shins, designed for sprinting

Long, lightly-built legs

Level back balanced by a long tail

Five-fingeredhand with tinyfifth finger

Small head withlarge eyes andstrong jaws

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DRY PLAINS RUNNER Heterodontosaurus lived in the Early Jurassic and was about the size of a large turkey. It roamed across the dry scrub of South Africa eating almost any plant material,including roots, which it may havedug up using the sharp claws on the inner “fingers” of its frontlimbs. These dinosaurs probablywandered through the scrub in small family groups, led by a dominant male. Whenthreatened, they couldrise up on their longhind legs and sprint away from danger,holding their long tails out behindthem for balance.

LESOTHO LIZARD

Scientific name: LesothosaurusSize: 3 ft 3 in (1 m) longDiet: PlantsHabitat: Semi-desertsWhere found: Southern Africa, VenezuelaTime: Early Jurassic Related genera: Possibly Scutellosaurus

SMALL BIPEDAL PLANT EATERS

DIFFERENT-TOOTH LIZARDA typical plant-eating dinosaur had a toothless beak, and its cheek teeth – used for grinding up plants – were all of one type.Heterodontosaurus (“different-tooth lizard”) was very different becauseit had three distinct types of teeth. Sharp upper incisors bit against a horny toothless beak in the lower jaw; ridged, high-crowned cheekteeth ground leafy plant foods to pulp; and long,curved upper and lower canines were used todeter and attack enemies and were displayedin fights between Heterodontosaurus males.The animal shut its jaws in a way thatmade the upper and lower cheekteeth slide over one another toproduce a grinding action. Itmay have stored unchewedfood in cheek pouches.

The pattern of teeth issimilar to that seenmodern mammals.

Tail stiffened by bony tendons

Long sharp canines with incisors to the front andcheek teeth to the rear.

Long, three-toed feet for fast running speeds

Licking may havehelped keep the paws clean.

Large gut to digestfibrous plants


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EARLY SHIELD BEARERS

DINOSAURS AND BIRDS


ARMORED SKINScelidosaurus’s hide was covered in tiny, pebblyscales and rows of bony studs. Small, low,bony plates – some ridged, some cone-shaped– added protection to its neck and back,while hornier bony plates formed clusters that protected the head. This knobby armorwas sufficient to resist attacks by Jurassictheropods, which had not yet developedpowerful muscles and sharp claws and teeth.

LOWER HIND LIMB LIZARDAmong the most primitive of theornithischian (“bird hipped”) dinosaurs wasScelidosaurus (“lower hind limb lizard”) fromthe Early Jurassic. When walking, it carriedits long, heavy body on four sturdy limbs,and was highest at the hips. Its long feet hadtoes with hooflike claws on their tips. Rowsof low, ridged, horn-sheathed bonesreinforced its skin. These, together with itscurved lower jaw and distinctive skull bones,identify Scelidosaurus as a thyreophorandinosaur. Although its front upper jaw hadteeth, these were not used for chewing butbit up and down, slicing and crushing thesoft “flowers” of palmlike plants.

Long, narrow,armored tail

Small, bony studs arranged in rows

BONY PLATESThese three scutes, or horny plates, give some idea of the body armor thatprotected Scelidosaurus from predators. If a theropod bit into the animal’s pebbly hide, its teeth would have come to a crunching full stop.

ARMED WITH SHOWY PROTECTIVE bony spikes and plates, stegosaurs and ankylosaurs rightly earned their name ofthyreophorans or “shield bearers.” Yet these ploddingquadrupeds – the dinosaur equivalents of armored cars –evolved from smaller, more agile plant eaters, whichmerely had rows of small bony plates and studs set intheir skin. Two of these early thyreophorans are knownfrom well-preserved Jurassic fossils. Scutellosaurus, whichwas built lightly to run on its long hind limbs lived inEurope, while the bigger, bulkier Scelidosaurus lived in Europe and North America. Incomplete fossils ofother early thyreophorans, including Emausaurus,Bienosaurus, and Tatisaurus, have also been found.

UNIVERSITY LIZARDEmausaurus was an early Jurassic herbivore, about 6 ft 6 in (2 m)in length. Its unusual name, which is short for “Ernst-Moritz-Arndt-Universität lizard,” comes from a university town innorthern Germany, where its fossil was discovered in 1990. Onlyparts of the skull, skeleton, and small pieces of its armor wereunearthed, so little is known about its habits. Like its relativesScelidosaurus and Scutellosaurus, Emausaurus was protected fromtheropod attack by flat and cone-shaped lumps set into its skin.

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LOWER HIND LIMB LIZARD

Scientific name: ScelidosaurusSize: 13 ft (4 m) longDiet: PlantsHabitat: River valleysWhere found: Europe and North AmericaTime: Early JurassicRelated genera: Emausaurus, Scutellosaurus

EARLY SHIELD BEARERS

Relatively small head for size of body

Scelidosauruswalked on all foursbut might havereared when in a hurry.

Small teeth in front of upper jaw

Tiny skull,probably withoutfleshy cheeks

Scutes and ossicles varied in shape.

Forelimbs muchshorter than hind limbs

Stocky bones insidelower hind limbs

LITTLE SHIELDScutellosaurus (“littleshield lizard”) had along body, slim limbs,and an elongated tail.More than 300 little,horn-sheathed, bonyscutes guarded its back,flanks, and the base of its tail. The largest scutesformed one or two rows downthe middle of the back. Scutellosauruscould walk on its hind limbs, its long bodybalanced by its even longer tail. However,its bony armor made its body heavy at thefront, so it probably also ambled on allfours. Scutellosaurus used its simple cheekteeth to slice and crush soft, fleshy, low-growing vegetation.


Wide hips

Hind limbsconsiderblylonger thanforelimbs

TUO RIVER LIZARD

Scientific name: TuojiangosaurusSize: 23 ft (7 m) longDiet: PlantsHabitat: Open woodlandWhere found: East Asia (China)Time: Late JurassicRelated genera: Lexovisaurus, Paranthodon

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PLATED DINOSAURSSTEGOSAURS (“ROOF LIZARDS”) WERE A GROUP OF four-legged, plant-eating dinosaurs that reached lengths of up to 30 ft (9 m). Named for the two rows of tallbony plates jutting up from the neck, back, and tail,most also had a pair of spikes jutting out from theirshoulders. Their bulky, ponderous bodies carriedcharacteristically tiny, low-slung heads. Stegosaurs first appeared in East Asia in Early Jurassic times, and by the Late Jurassic the group included Tuojiangosaurusfrom China, Kentrosaurus from East Africa, Lexovisaurusfrom Europe, and Stegosaurus from North America andEurope. Late Jurassic times were their heyday, and thegroup seems to have petered out in Early Cretaceoustimes. Perhaps their spiky defenses proved no match fornew formidable kinds of theropod dinosaur.

Tuojiangosaurus skeleton

DINOSAURS AND BIRDS



Stegosaurus skull and ridged cheek tooth

Bones of the forelimbsmuch shorter thanthose of the hind limbs

The forelimbs may havebeen erect or splayed out at the elbows.

SKULLS AND TEETHMost stegosaur skulls were long, low, and narrow, ending

in a slim, toothless beak. The jaws were hinged lowdown at the back and had small, ridged cheek

teeth set in from the sides. Fleshy cheeks mayhave stopped food from falling out of the

mouth when eating. Stegosaurs musthave consumed huge amounts

of plant matter to sustaintheir great bulk.

TUOJIANGOSAURUSThe Chinese dinosaur Tuojiangosaurus (“Tuo River lizard”) was longerbut lighter than a rhinoceros. Its skeleton clearly shows a low skull,high, humped back, long, heavy tail, and solid limb bones. Up to 15pairs of pointed bony plates rose from this stegosaur’s neck, back, and tail. Two pairs of long, slim spikes stuck up and out from the end of the tail, and a long spine jutted from each shoulder. Hornysheaths would have covered the tail and shoulder spikes,making these even longer than their bony cores suggest.

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SPIKY BACKKentrosaurus (“sharp point lizard”) takes its name fromthe long spines that stuck up from its back, tail, andflanks. Up to 17 ft (5 m) in length, this stegosaur had along but narrow skull, which was held low off the groundwhen walking. Its jaws were equipped with small cheekteeth to browse ferns and other low-growing plantsthat grew along river banks. The back legs were twice as long as the front legs, suggestingthat Kentrosaurus could rear up to reachhigher vegetation.

PLATED DINOSAURS

ONE BRAIN OR TWOFor such a large dinosaur, Kentrosaurus had a small brain – no bigger than a walnut. However, the olfactory bulb was welldeveloped, giving the animal a good sense of smell. It was oncebelieved that the tiny brain was too small to control the animal’sbody and that another larger brain was located near the hips, as inother dinosaurs. Scientists now know that the larger “brain” cavitymerely held nerves that controlled the hind limbs and tail, andmaybe stored glycogen – food energy for powering its muscles.

Conical bony plates weretallest over the hips.

Unlike mostornithischians,stegosaurs lackedbony tendons tostiffen the tail.

Deep tail

Two rows ofspikes, each upto 2 ft (60 cm)in length

Cast of Kentrosaurus’slarger “brain,” which filleda hollow in two vertebrae.

Cast of the truebrain, which waswas located in theanimal’s small head.

Hooflike clawson toes

Four tail spikes for defense

Short, massivefoot bones

172


DINOSAURS AND BIRDS



SPIKY BACKS

STING IN THE TAILStegosaurus was well protected by a tough, studded hide, and it wasalso able to deter predators with its mace-like tail. Sticking out andback from the end of the tail wereat least two pairs of long, sharpbony spikes, covered in horn.Standing alongside an attackingAllosaurus or other predator,Stegosaurus could have lashed its tail, inflicting frightful stabbing blows.

Broad hind foot withthree short, blunt toes.

Downcurvedneck held thehead low off the ground.

THE MOST STRIKING FEATURE of any stegosaur is the array of plates sticking up from its neck, back,and tail. The largest member of this group wasStegosaurus (“roof lizard”) – a North American andEuropean dinosaur that could grow to the size of abus. Its back was crowned by huge plates shaped likeupended sidewalk slabs. The first Stegosaurus fossilwas discovered in the western United States in the1870s, and dozens have been unearthed since.Despite being one of the most intensely studiedof all dinosaurs, experts forlong disagreed about how theplates were arranged on thegiant’s back and about theirfunction. Were theyfor defense or forshow, or did theyhelp regulatetemperature?

Four-toedforefoot withtoes tipped byhooflike nails

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SPIKY BACKS

PLATE DEBATEScientists once thought that the paired bony plates onStegosaurus’s back protected it from attack. This nowseems unlikely, because the plates were made of thinbone and were probably covered with skin, not horn.Instead, they perhaps served as radiators, helping

Stegosaurus to warm up when it turnedperpendicular to the Sun’s rays,

and to cool down when itturned away. Another theory

is that the plates were forshow, helping males and

females of the same speciesto recognize each other.

The plates alternatedrather than formingtwo paired rows.

CHAINMAILStegosaurus’svulnerable throat wasprotected from the claws andteeth of theropods by bony studs set in theskin. These studs – also present on the hips,thighs, and tail – were the equivalent of thechainmail worn by medieval knights. They preventedpuncture while leaving the skin itself quite flexible.

Although small,the braineffectivelycoordinated thebulky body.

The narrowbeak wassuited tocropping low-growing soft,fleshy plants.

ROOF LIZARD

Scientific name: StegosaurusSize: Up to 30 ft (9 m) longDiet: PlantsHabitat: Open woodlandWhere found: North America and EuropeTime: Late JurassicRelated genera: Tuojiangosaurus, Wuerhosaurus

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NODE LIZARDSTHE ARMORED DINOSAURS CALLED ANKYLOSAURS (“fusedlizards”) were heavily plated, four-legged plant-eaters.They had characteristic low-slung heads, fairly shortnecks, broad, barrel-shaped bodies, and long, rather thicktails. These tanklike beasts were too slow to sprint awayfrom danger, and their stubby claws and small, ridgedteeth were no match for a large theropod’s talons andfangs. Instead, they relied for protection on bony platesor spikes sheathed with horn and set into their thick,tough hides like cobblestones in a road. Ankylosaurs’armor may have proved more effective than thedefenses of stegosaurs, relatives that theyreplaced. First emerging in the Jurassic,ankylosaurs spread through northerncontinents during Cretaceous times, andappeared as far south as Australia andAntarctica. Their three main groupswere nodosaurids (“node lizards”),polacanthids, and ankylosaurids.

ARMORED GIANTAs long as a soccer goal

is wide and twice the weightof a large rhino, Edmontonia

was one of the largest and latest ofthe nodosaurids. These ankylosaurstended to have a fairly narrow, pear-

shaped skull, covered with big scales,protecting the braincase. Many had spikyshoulder spines, but none had a tail club.

Edmontonia shielded the back of its neck with two collars of flatbony plates. A third collar lay between the shoulders, and rows of

smaller, ridged bony plates covered the rest of the back and tail.Long, bony spikes projecting from the shoulders were its main

weapons, and could have crippled an attacking tyrannosaur’s leg.

DINOSAURS AND BIRDS



Ankylosaurs probablyhad roomy cheeks tohold food beingchewed

Mouth ending innarrow beak

Second collar ofbony plates

Long bony spikeguarding the shoulder

First collar ofbony plates

Ridged, bony,horn-coveredscute (“shield”)

Spike protectingagainst a flankattack

Short, broad,sturdy foot

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ARMORED HIDESauropelta (“shielded lizard”) from the EarlyCretaceous of North America was smaller and lessheavily armored than Edmontonia. Seen fromabove, Sauropelta’s armor resembles a knight’schain mail. Rows of bony cones set among smallstuds protected its back but left its body quiteflexible. Bony spikes jutted from the sides of itsneck. If attacked, Sauropelta might have crouchedto guard its unarmored belly.

AN ARMORED DINOSAUR DOWN UNDERFound near Minmi Crossing in Queensland, Minmiwas the first armored dinosaur discovered south of the Equator. At only 10 ft (3 m) long, this EarlyCretaceous ankylosaur was smaller than most others.

Small bony plates guarded its belly, and besideeach dorsal vertebra was a bony platejoined to a bony rod that might havehelped to reinforce its backbone. Such

unusual features make scientists suspectthat Minmi was neither a nodosaurid nor an

ankylosaurid, but belonged to another, so-farnameless group of armored dinosaurs.

NODE LIZARDS

EDMONTONIA

Scientific name: EdmontoniaSize: 23 ft (7 m) longDiet: Low-growing plantsHabitat: Open woodlandWhere found: North AmericaTime: Late CretaceousRelated genera: Panoplosaurus, Sauropelta

Largest bonyplate overbraincase

Impressions oflarge scales

Sharp, low platesshielding hips

Raised bony shieldson the hindlimb

Tall, ridged scutesover shoulders

Broad-based “thorny”plates guarding tail

Rows of ridged platesrunning downmuscular tail

Fossilized Sauropelta hide

Edmontonia skull

SHEEPLIKE HEADEdmontonia’s skull looked much like a sheep’s head when seen fromone side. Its narrow, toothless beak was probably suited to croppingsoft, juicy, low-growing plants, which were then sliced up by itssmall, ridged cheek teeth. A top view shows bony plates tightlyfitting together like bits of a jigsaw puzzle to thicken the skull. A theropod’s teeth might have simply skidded off Edmontonia’s skull like human teeth trying to crunch up a coconut shell.

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FUSED LIZARDSTHE ANKYLOSAURIDS (“FUSED LIZARDS”) were armoreddinosaurs 10–33 ft (3–10 m) long. Like their relativesthe nodosaurids, their main defenses were the thick,solid bones of the skull, and bands of bony plates,studs, and spikes shielding the neck and back.Unlike nodosaurids, most ankylosaurids had a skull asbroad as it was long, with small “horns” projectingfrom the back, and a convoluted airway inside. Theircommon feature was the massive bony club on theend of the tail, and some early “ankylosaurids”without a club arguably formed a third family, calledthe polacanthids. The ankylosaurids appeared by the

Late Jurassic and thrived throughout theCretaceous in Asia, North America, andEurope. Some Late Cretaceousankylosaurids were the largest armored dinosaurs of all.

THORNY BEASTNamed after fossilhunter RobertGaston, Gastoniaresembled a walkingthorn bush the length

of a large car. Gastoniaroamed Utah in Early

Cretaceous times. Big spines stuck out sideways from its shoulders andtail, and two rows of long spines stuck up from its back. Many smallerbony spines and a bony shield across its hips completed this dinosaur’sjaw-breaking defense. Gastonia’s broad skull resembles an ankylosaurid’s,but it was in fact a polacanthid. Despite the lack of a club, spines couldhave made its tail a formidable weapon.

AN ANKYLOSAURID SKULLThis reconstruction reveals Euoplocephalus’s bizarrelyarmored skull. Thick skull bones with a “crazy paving”pattern closed holes that lightened the skull in otherdinosaurs. Its bony eyelid could flick up or down, likea window shutter, to protect the eye. Broad, short,thornlike spikes projected at the rear,protecting the back of the skull. Behind theheavy, toothless beak, the cheek teethseem tiny and inadequate. They merelysliced up soft plant foods that weremainly mashed up in the gut.

WELL-ARMORED HEAD

Scientific name: EuoplocephalusSize: 23 ft (7 m) longDiet: Low--growing plantsHabitat: Open woodlandWhere found: North AmericaTime: Late CretaceousRelated genera: Ankylosaurus, Pinacosaurus

DINOSAURS AND BIRDS



Spine-fringed tail couldlash from side to side.

Broad, flat spikes toward off attack fromthe side

Muscular tail could swingclub from side to side.

Thickened bonegave the tail a clubshape.

Pattern wherescales were stuckto the skull

WELL-ARMORED HEADResembling a cross between an armadillo and a huge rhinoceros,Euoplocephalus (“well-armored head”) was one of the most commonankylosaurids of Late Cretaceous North America. With its broad beak,Euoplocephalus would not have been a choosy feeder – its main foodswere very likely ferns, and the weedy, soft-stemmed flowering plants now

spreading north. As it ambled slowly across woodlandglades, four sturdy limbs bore theweight of its barrel-shaped bodyand the heavy load of plant foodin its gut. If it had to,

Euoplocephalus could breakinto a trot, but speed

was not its bestdefense.

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BONY TAIL CLUBThis fossil shows theconstruction of what wasprobably an ankylosaurid’s maincounterattacking weapon. At thetip of the tail, four swollen bonylumps – two large and two small –had fused to one another and the tail-tip vertebrae. Outside these bones, long,ropelike tendons stiffened and reinforced the tail’stip. The tail’s muscular base was flexible, though –free to swing the club from side to side, delivering a heavy, powerful blow. Any attacking tyrannosauridmight have risked a fractured shin or ankle.

FUSED LIZARDS

Short and broadthree-toed feet

Short digits withblunt nails

Bony tendonsreinforced end ofthe tail.

Bony “thorns”tallest over theshoulders

Broad toothless beakfor cropping lowvegetation

Pointed scutesran in rows downback.

Broad thighspartly supportedby wide, shelf-shaped hipbones

Lateral divisionbetween bands

One of twolarge bony tailplates

One of twosmall bonytail plates

Flexible armoredbands on back

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CAMPTOSAURS AND DRYOSAURSIGUANODONTIANS EVOLVED during the Jurassic.They were extremely successful ornithopod (bird-footed) dinosaurs and include thefamous Iguanodon. The most primitiveiguanodontians, such as Dryosaurus, wererelatively small and lightly built and wouldhave relied on fast running to escape frompredators. They might have used their armsfor walking when moving very slowly, but, incontrast to Iguanodon, their arms and fingers wereshort. Unlike earlier ornithopods, iguanodontians did not have teeth at the tip of their upper jaw. With the evolution of Camptosaurus, iguanodontiansbegan to become larger, heavier, and less agile.

DINOSAURS AND BIRDS



CAMPTOSAURUSThe best-known camptosaur was Camptosaurus from the LateJurassic and Early Cretaceous of North America and England. It hadstout hind limbs, a skull with a long snout, and a large, deep body.Camptosaurus was originally named Camptonotus meaning “flexibleback.” This was because the hip vertebrae of the first specimenseemed not to be fused together. However, Camptonotus had alreadybeen given to another animal, so Camptosaurus, meaning “flexiblelizard” was chosen. In fact, Camptosaurus does have fused hipvertebrae like other dinosaurs, so the name is inaccurate.

Palpebral bone

IGUANODONTIAN SKULL Features of such skulls show thatiguanodontians were well suited forcropping and chewing plant material. The toothless beaks of the upper and lowerjaws were broad and would have had sharpcutting edges. Mobile joints allowed the cheeksto move in and out so that the teeth in theupper jaw could grind against those in thelower jaw. An unusual bone called thepalpebral grew across the eye socket, but itsfunction is unknown.

Camptosaurs had long heads with beaked lower and upper jaws.

Camptosaurus had strongarms. Fossil tracks suggestthat it may sometimes havewalked slowly on all fours.

The teeth wereleaf-shaped withserrated margins.

The arms were slim and thehands were small. Hatchlings hadstronger forelimbs and appear tohave walked on all fours.

Dryosaur legs and feet werebuilt for fast running. Unlikein Camptosaurus, the smallfirst toe was not present.

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CAMPTOSAURUS

Scientific name: CamptosaurusSize: 16 ft (5 m) longDiet: LeavesHabitat: Open woodlandsFossil finds: North America and EnglandTime: Late Jurassic and Early CretaceousRelated genera: Callovosaurus

CAMPTOSAURS AND DRYOSAURS

The bones of thelower part of thepelvis are directedbackward to allowspace for larger guts.

DRYOSAURUSDryosaurs have been found inNorth America, Africa, and Europe.The name means “tree lizard” andis a reference to the idea that thisdinosaur lived in a woodlandenvironment. Dryosaurs have shortskulls with large eyes. Theirpeculiar nostrils are not coveredover on their upper side by a bonybridge, as they are in virtually allother dinosaurs.

HAND OF CAMPTOSAURUS Camptosaurus had five shortfingers, the first three of whichhad hooves. Fossil trackwaysshow that its fingers were notjoined together in a large padas they were in Iguanodon.Several of the wrist bones werefused together, perhaps forstrength when the hand wasused to support weight.

The last thumb bone was apointed, spurlike structure. Itwas different from thespecialized thumb spikeseen in Iguanodon.

Hooflikefingertip

Crisscross patternof tendons

VERTEBRAE OF CAMPTOSAURUS Like other ornithopods, Camptosaurus had a criss-cross pattern of tendons growing on the sides ofthe spines of its vertebrae. Arranged in threeoverlapping layers, these helped reinforce thespine and keep the back stiff. Its sacrum – the partof the vertebral column where the vertebrae areconnected to the pelvis – consisted of either five orsix vertebrae. Camptosaurus shared with Iguanodonspecial peg-and-socket joints between each of thesacral vertebrae. These further helped reinforcethe backbone.

Camptosaurs have massive toebones. The small first toe isturned backward and wouldnot have reached the ground.

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DINOSAURS AND BIRDS

PECULIAR HANDSIguanodon has the most specialized hands of any dinosaur. They could have been used as weapons, for walkingon, and for grasping vegetation. A largeconical spike, originally thought to belocated on the tip of the nose, turnedout to be Iguanodon’s highly modifiedthumb. The second, third, and fourthfingers are strongly built and webbedtogether, and tipped with blunt hooves.Its fifth finger is slim and flexible.

IGUANODONFOSSILS OF IGUANODON have been found in Europe andNorth America, and it is one of the best-known andmost successful dinosaurs. Officially brought toattention in 1825 by Gideon Mantell, a doctor from Lewes, England, it was the seconddinosaur after Megalosaurus to be named anddescribed. Mantell thought that Iguanodon wasan immense lizardlike animal, while otherscientists of the time argued that it resembleda rhinoceros more. In 1878, numerouscomplete skeletons were discovered in a coal mine in Belgium, which showedwhat Iguanodon really looked like. It had stout legs, three-toed feet,powerful arms with a thumbshaped like a spike, and a vaguelyhorselike skull with a toothlessbeak. Fossilized footprintssuggest that Iguanodonmoved around in herds.



Scientists once believed thatIguanodon’s tail would have slopeddown close to the ground as shownhere. More recent research hasshown that this was not thecase. Like virtually all dinosaurs,the structure of Iguanodon’sspine suggests that its tail wouldhave been held horizontally and off the ground.

Iguanodon’s powerful arms werelong enough to reach the ground.The three middle fingers appearsuited for bearing weight. Thesefeatures suggest that Iguanodonoften walked on all fours.

The woodland habitatof Iguanodon containedgiant tree ferns andconifers, and horsetailmeadows. Floweringplants such asmagnolias had alsoevolved by this time.



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IGUANODON

Iguanodon was stoutly builtand probably walked with itsbody held horizontally formost of the time.

VEGETARIANIguanodon was a large browsingherbivore with a deep skull,toothless beak, and manypowerful cheek teeth. Special hinges in the skull and

mobile lower jaws allowedIguanodon to chew tough

plants. Its height mayhave allowed it to feed from trees.

IGUANODON

Scientific name: IguanodonSize: 26-40 ft (8-12 m)Diet: Leaves, branches, fronds, and fernsHabitat: WoodlandsWhere found: Europe and North AmericaTime: Early Cretaceous Related genera: Altirhinus, Ouranosaurus



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IN THE CRETACEOUS an important group called the hadrosaurs(“duck-billed” dinosaurs) descended from Iguanodon-likeancestors. As their name suggests, duck-billed dinosaurs are characterized by an expanded toothless beak. They hadhundreds of tightly packed teeth that were well equipped to grind up tough vegetation. Some had bizarre crests.Duck-billed dinosaurs are best known from North Americaand eastern Asia but they are also known from Europe, South America, and Antarctica. They were among thebiggest dinosaurs, but they were preyed on by tyrannosaursand other theropods. An old theory is that the hadrosaurswere amphibious animals, but their stiff tails, short toes, and small hands show that they more likely lived on land.Fossilized tracks, piles of bones, and nesting sites suggest that they were herding animals and formed nesting colonies.

CORYTHOSAURUSCorythosaurus was a crested duck-billed dinosaur, with a crestthat was shaped like a plate. The name Corythosaurus means“helmet lizard,” referring to the similarity between its crest andthe helmets worn by soldiers in ancient Greece. Corythosaurusis one of the best-known hadrosaurs thanks to the discoveryof a complete skeleton in 1912. The similar-lookingHypacrosaurus is probably a descendant of Corythosaurus.

Duck-billeddinosaurs had losttheir thumbs, andtheir forelimbs wereslimmer and lesspowerful than in Iguanodon.

Skull featuresshow that duck-billed dinosaurshad large eyes,acute hearing,and a goodsense of smell.

DINOSAURS AND BIRDS


MAIASAURA FAMILYMaiasaura was a flat-headed duck-billed dinosaur. Like otherhadrosaurs without crests, it had hollow areas around thenostrils which perhaps housed large, inflatable skin pouches. It has been preserved with nests, broken eggshells, and babies.The babies clearly stayed in the nest for some time afterhatching (as shown by the trampled eggshell) and thereforethey may have been cared for by their parents.

Hatchlings wereabout 20 in(50 cm) long.

DUCK-BILLED DINOSAURS


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299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Neogene 23–present


LAMBEOSAUR CRESTSDuck-billed dinsoaurs with crests were calledlambeosaurs. These crests were hollow with acomplex series of tubes inside, and the shapevaried tremendously between species andindividuals. The crests are connected tothe noses and throats of the animals.Lambeosaurs probably used themas resonating devices, with thevarious shapes creatingdifferent sounds.

Stiff and narrow tail

Stout andpowerful hind limbs

In Lambeosaurusthe main part ofthe crest wastilted forward.

Parasaurolophushad a backwardpointing tube.

Evolution of thecrest resulted in the nostrilsbeing pulledbackward.

Hadrosaur skinwas covered insmall, roundedtubercles.

CORYTHOSAURUS

Scientific name: CorythosaurusSize: 40 ft (12 m) longDiet: Plants including leaves, twigs, pine needlesHabitat: ForestsWhere found: Western North AmericaTime: Late CretaceousRelated genera: Hypacrosaurus, Lambeosaurus

DUCK-BILLED DINOSAURS

Parasaurolophus skull Hypacrosaurus skull

SWAMPLANDCorythosaurus is shown here wadingthrough a forest swamp. Most hadrosaurslived in warm plains between the RockyMountains and a vast inland sea thatdivided North America into western andeastern halves. As well as cypress swamps,there were pine forests, fern prairies, andcoastal marshes. The first flowering plants– the plants and trees that dominate theworld today – were beginning to spread.

Lambeosaurus skull

Triassic 251–199.6

Fossilized tracksshow that duck-billed dinosaursoften walked on all fours, thoughthey could walk ontwo legs as well.

Paleogene 65.5–23


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THICK-HEADED LIZARDSPACHYCEPHALOSAURS WERE CRETACEOUS DINOSAURS that are famous forhaving specially thickened bones on the tops of their skulls. In some,such as the Late Cretaceous North American forms Pachycephalosaurusand Stegoceras, the top of the skull formed a thickened dome, shapedlike a bowling ball. Others, such as Homalocephale from Mongolia, hadflat skull roofs. All known pachycephalosaurs come from the northernhemisphere and most are smaller than humans. Many specimens havebeen found in North America and Asia. A small pachycephalosaurfrom the Late Cretaceous of China is distinguished by having thelongest name of any dinosaur – Micropachycephalosaurus.

STEGOCERASStegoceras was a medium-sized, round-skulledpachycephalosaur. It is one of the fewpachycephalosaurs for which not only skullsare known but also other skeleton parts. Ithad a large expanded chamber at the baseof its tail, the function of which is unknown.

DINOSAURS AND BIRDS



Prominent ridges growalong the side of theskull and over the eyes.

The end halfof the tailwas stiff andinflexible.

The hips broadentoward the baseof the tail.

Pachycephalosaurshad curved, fangliketeeth at the front ofthe mouth. They also had beaks.

Its straight, stiff tailwould have helpedPachycephalosauruskeep its balance.

Stegoceras

More skulls ofStegoceras havebeen found thanof any otherpachycephalosaur.

Slim leg and foot boneswould have allowedPachycephalosaurusto run quickly.

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BONY SHELFAll pachycephalosaurs have abony shelf jutting out from theback of their skulls, as seen onthe Stegoceras example above.The related genus Prenocephalehas a less distinct shelf. Thebony shelf is also seen in the ceratopsians (horneddinosaurs). Thus, pachycephalo-saurs and ceratopsians areunited in a group called theMarginocephalia (“margin-headed ones”).

Skull and mandible of Stegoceras

Skull of Prenocephale

PACHYCEPHALOSAURUS

Scientific name: PachycephalosaurusSize: 15 ft (5 m) longDiet: Leaves, fruit, perhaps small animalsHabitat: ForestsWhere found: North AmericaTime: Late CretaceousRelated genera: Prenocephale, Stygimoloch

THICK-HEADED LIZARDS

PACHYCEPHALOSAURUSThe thickened skull roofs of dome-headed pachycepha-losaurs suggest that these dinosaurs used their heads for fighting off rivals during the breeding season, much

like goats and sheep do. However, the skull roof in goats andsheep forms a contact area that can be more than 12 in (30 cm)wide. In contrast, the bowling-ball shape of dome-headedpachycephalosaurs would have a small contact area, whichwould have placed a dangerous sideways strain on the neck. If pachycephalosaurs did not butt heads, they may have buttedeach other’s bodies instead. Features of the vertebrae suggestthat their spines may have had some shock-absorbing ability.

Prenocephalehad a less

distinct,rounded shelf.

The bony shelf is one ofthe features common toall pachycephalosaurs.

The top of the head of Pachycephalosauruslooks like the shape of a bowling ball.

The arms and hands of Pachycephalosaurusare small in proportion to the very broad body.

PSITTACOSAURUSEleven different species, all in genusPsittacosaurus, are distinguished byproportions, features of the teeth, andshape of the skull. Psittacosaurs have four fingers on the hand, unlike later ceratopians which all have five fingers. This suggests thatpsittacosaurs were not theactual ancestors of laterceratopsians. Psittacosauruswas around for about 30 million years, making itone of the longest liveddinosaur genera.

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PARROT LIZARDSPSITTACOSAURS (PARROT LIZARDS) were small bipedal (two-footed)ornithischians (bird-hipped dinosaurs) that have proved abundant inthe Lower Cretaceous rocks of eastern Asia. Their short, deep skullsare like those of modern parrots. Originally classified as ornithopodsrelated to Hypsilophodon, psittacosaurs were laterrecognized as relatives of the horned dinosaurs of theLate Cretaceous. Both these groups possess a uniquebone (the rostral) at the upper jaw’s tip. Except forYinlong and Chaoyangsaurus, psittacosaurs are themost primitive known ceratopsians. Elongated,slim hindlegs suggest they were fast runners, andthis is probably how they escaped from predators.More than 100 specimens are known.

LITTLE BABIESBaby psittacosaurs are among the smallest reporteddinosaur fossils. One specimen is estimated to havebeen 9 in (23 cm) long. Like other baby animals,these psittacosaurs have huge eyes, short snouts, andproportionally larger heads than adults. Some babies

are found preserved together,suggesting that they stayed

in groups. As with manydinosaurs, experts are unsureas to whether the babies werecared for by their parents, or

if they were independent.

FOSSILIZED PSITTACOSAURUSSkeletons are often found in desert areas with sand dunes. This suggests that Psittacosaurus was adaptedto life in dry environments.Several psittacosaur specimensare preserved as if lyingon their bellies, theirlegs folded upunderneath them.One expert hassuggested thatthis shows theirlegs had greatmobility.

Like most ornithischians,psittacosaurs had bonytendons arranged alongthe length of their tail.

Psittacosauruswould have runaround on its hind legs.

DINOSAURS AND BIRDS



Actual size skull of fossilizedbaby Psittacosaurus This skeleton,

found in the1920s, was thefirst psittacosaurto be discovered.

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PARROTLIKE HEADSThe psittacosaurs’ remarkably deep skulls aresuperficially like those of parrots. Their toothlessbeaks and blunt teeth suggest that they wereherbivores, but they could have been omnivoresthat also ate carrion and small animals. Unlikelater ceratopians, psittacosaurs swallowed stonesand used these to help grind up their food.

Unlikepsittacosaurs,parrots canmove theirupper jawindependentlyof the rest ofthe skull.

The rostralbone, aparrotlikebeak

Long toes andsharp clawssuggest thatPsittacosauruscould have been a good digger.

Horns,perhaps usedin fighting ordisplaying,project fromthe cheek.

Like many other similardinosaurs, psittacosaurs had bones called palpebralsjutting out above theireyeballs. Experts remainunsure as to what these were for.

Psittacosaurus skull

Modern parrot head

PSITTACOSAURUS

Scientific name: PsittacosaurusSize: 7 ft (2 m)Diet: Plants, perhaps small animalsHabitat: Desertlike scrublandWhere found: North, East, and Southeast AsiaTime: Early CretaceousRelated genera: Chaoyangsaurus, Yinlong

PARROT LIZARDS

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THE GROUP OF HORNED DINOSAURS called the Neo-ceratopsia (“new horned faces”) can be dividedinto primitive and advanced forms. Theearly horned dinosaurs did not havethe large horns of the advancedforms and they were relativelysmall, at about 3–12 ft (1–4 m) long. Earlyneoceratopsians probably ate mainly plants. Unlike their ceratopsiddescendants, some of these early neoceratopsians had pointed teethin their upper jaws. These primitive neoceratopsians were mostlyfrom eastern Asia, including the well-known Protoceratops. Severalothers, including Montanoceratops, were North American.

PROTOCERATOPSProtoceratops is one of the few dinosaursknown from tens of specimens. Inthe Gobi Desert in Mongolia itsfossils are so abundant that fossil-hunting paleontologists there callit the “sheep of the Gobi.”Individuals with larger, tallerneck frills and deeper snoutsappear to be males.Protoceratops has very tallspines on the top of its tailvertebrae, which wereperhaps used in display.

STAGES OF DEVELOPMENTBecause of the abundance of Protoceratops specimens, expertshave been able to make a detailed study of the different stagesof development. Specimens range from tiny babies to full-grownadult males and females. These reveal important changes thatoccurred in proportions during growth, particularly in the frill,as can be seen in the sequence of skulls shown here. Up to thejuvenile stage, the frill or snout shape does not differ betweenmales and females. Older females have narrow frills and lowsnouts, while older males have larger cheeks, snout, and frills.

Hatchling BabyJuvenile

Subadult –possibly male

Subadult –possiblyfemale

Adult –possibly female

Adult – possibly male

The deep tail was originallythought to indicate thatProtoceratops could swim.However, the animal livedin a desert.

Protoceratops had long,slender limbs suggestingthat it was a fast runner.



DINOSAURS AND BIRDS

BURIED IN SANDSeveral Protoceratops specimens from Mongolia are preserved buriedin sand. Perhaps these were killed when the sand dunes they werehiding behind collapsed on top of them. Because their bones werethen protected from scavengers, these specimens are very wellpreserved. Some of them are preserved intwisted or standing positions.Apparently Protoceratopsbabies clustered together.

EARLY HORNED DINOSAURS

The skeleton is seen herefrom beneath. Protoceratops preserved in sand

Most horned dinosaur frillshad thin bony borders andskin-covered gaps in thebone. These suggest thatthey were not for theattachment of large jawmuscles as once thought.

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FOSSILIZED PROTOCERATOPSFIGHTING VELOCIRAPTOR This famous fossil was discoveredin the Gobi Desert in 1971.It preserves a Protoceratops lockedin combat with a Velociraptor.Both animals appear to havedied while fighting. This mightbe because they both died oftheir injuries, or it might bebecause they were buried by asand dune as they fought.

Protoceratops

The Velociraptor’sarm is gripped by theProtoceratops’ beak.

Two pairs of fangliketeeth may have beenused in fighting or biting.

Protoceratops had a very small nasal hornbetween the eyes. The nasal horn waspresent in all advanced horned dinosaurs.

Some Protoceratops fossilsinclude the bony rings thatsupported the eyeballs. Theseshow that the eyes were large.

PROTOCERATOPS

Scientific name: ProtoceratopsSize: 7 ft (2.5 m) longDiet: Mostly desert vegetationHabitat: Desert and desertlike scrublandWhere found: East Asia Time: Late CretaceousRelated genera: Bagaceratops, Udanoceratops,Leptoceratops

EARLY HORNED DINOSAURS

Velociraptor

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IN THE LATE CRETACEOUS a group of horned dinosaurs, called theceratopsids, developed. These were distinguished from earlier horneddinosaurs by their mostly large body size, hooflike (rather thanclawlike) bones on their fingers and toes, and large horns. They wererobust, short-tailed, four-legged dinosaurs that superficially resembledhorned rhinos today. All have massive hooked beaks and shearingteeth and would have been highly efficient eaters of most kinds of

plant material. With the exception of twocontroversial fragmentary specimens from

eastern Asia and South America, allknown ceratopsids are NorthAmerican. At least 19 differentgenera evolved there.

STYRACOSAURUSA group of horned dinosaurs calledthe centrosaurines had relatively smallbrow horns and enlarged nose horns.Some centrosaurines also grewprominent backward-pointing spikeson the back of the frill. This trend wascarried to its extreme in Styracosaurus,a genus that has six markedly elongatespikes on the back of the frill. Thespikes would have looked imposing if the head was dipped in display.

CENTROSAURUS Centrosaurus is a commonhorned dinosaur. Its nose hornis sometimes straight andpoints upward, as here. Inother individuals it curvesbackward or forward tooverhang the tip of the snout.

Straightnose horn

Many advanced horneddinosaurs have bones calledepoccipitals arranged aroundthe edges of the frill. The largefrill spikes of Styracosaurus areprobably enlarged epoccipitals.

Like other centrosaurines,Styracosaurus had an enlargedelongate nasal horn.

Centrosaurines have enormousnostril openings and incrediblydeep snouts. The function ofthese nostrils is unknown.



DINOSAURS AND BIRDS

ADVANCED HORNED DINOSAURS

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TRICERATOPSThe most famous horneddinosaur is Triceratops, a member ofthe chasmosaurine group. Chasmo-saurines mostly had elongate frills withlarge openings, but Triceratops is unusualin having a fairly short frill that lacksopenings. Growing to 30 ft (10 m) inlength and weighing about 9.8 tons (10 tonnes), it was a gigantic animal

and one of the last nonbird dinosaurs.

The hips areconnected to about10 vertebrae bones– more than in anyother dinosaurgroup, except birds.

Like other horned dinosaurs, thebody of Styracosaurus wascovered in a thick hide.

The robust four-toed feet were builtto support weight. The hooves wereblunt, unlike the clawlike hooves ofmore primitive horned dinosaurs.

Some expertsthink that horneddinosaurs couldgallop despite theshortness oftheir limbs.

LIFE AND DEATH IN HERDSAt least some horneddinosaurs appear to havebeen herding animals.Like living wildebeest,shown here, and otherherding mammals, manyhorned dinosaurs seemto have drowned duringthe panic of rivercrossing. Their boneswere then trampled andscavenged by theropodsand other animals.

ADVANCED HORNED DINOSAURS

STYRACOSAURUS

Scientific name: StyracosaurusSize: 17 ft (5 m) longDiet: Ferns, cycads, and other plantsHabitat: Open woodlandWhere found: North AmericaTime: Late Cretaceous Related species: Achelousaurus, Einiosaurus

The nose hornand two browhorns giveTriceratops itsname, whichmeans “three-horned face.”

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Mammals and their Ancestors

Sprawling, scaly pelycosaurs with tall fins on their

backs, featured below, look nothing like tigers or

cows. Yet the pages in this section show that today’s

hairy, warm-blooded mammals all owe their origins

to such reptile-like creatures. Startling images

reveal other prehistoric mammals that looked

just as strange as pelycosaurs – elephantine sloths,

snaky whales, cats with dagger-like canine teeth,

and hoofed mammals with bizarrely horned

heads. Discover extinct ape-like creatures that

walked erect, and their increasingly intelligent

descendants – the mammals called humans.

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SYNAPSIDS CLADOGRAM


EXTINCT RELATIVESOF MAMMALS

XENARTHRANS

GLIRES

CARNIVORES

SYNAPSID OPENINGThe opening in the skullbehind the eye socket iscalled the synapsid opening.It may have evolved toprovide new attachment sites for jaw muscles.

THREE MIDDLE-EAR BONESAll mammals possess threemiddle-ear bones. Thesesmall, distinctive ear bonesevolved from bones that once formed part of the joint linking the back of the skull with the lower jaw.

PLACENTAA developing babyexchanges substances withits mother via the placentaattached to the mother’suterus. The placenta letsplacental mammals retaintheir babies internally untilthey are well-developed.

Early PermianpelycosaurDimetrodon

Xenarthrans includeclimbing, digging, and swimming forms.Ground sloths, such asthis Megatherium, werehuge plant eaters.

The duck-billed platypusis a monotreme.

MONOTREMES, MARSUPIALS,MULTITUBERCULATES, AND TRICONODONTS

Dimetrodon skull

Eye socketSynapsidopening

Middle-earbones

Cross-section of a human ear

The placenta is a mass ofspongy tissue.

Human foetusat 28 weeks

Uterus

MAMMALS AND THEIR EXTINCT RELATIVES are called synapsids. Theseamniotes are named after the bony opening behind the eye, known as the synapsid opening. Typical mammalian features, such as fur, a warm-blooded metabolism, and a lower jaw that consists of a singlebone, appeared gradually during synapsid evolution. True mammalsevolved in the Triassic. The earliest members of the three livinggroups – the egg-laying monotremes, the pouched marsupials, and the placentals – appeared in the Cretaceous. Placental mammals include the most familiar synapsid groups.

SYNAPSIDSSynapsid opening

MAMMALSThree middle-ear

bones

PLACENTALSPlacenta

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INSECTIVORES ANDARCHONTANS

CETACEANS PERISSODACTYLS

SIRENIANS

ARTIODACTYLS

STIRRUP-SHAPED STAPESIn epitheres, the middle-ear bonecalled the stapes is stirrup-shaped.This shape made it lighter andbetter able to respond to highfrequency sounds. Epitheresinclude all placental mammalsexcept xenarthrans.

HOOFUngulates have hoovesthat grow over the endbones of the digits, andform a strong structure for running. Most of thebody’s weight is carried on the middle digit, somany ungulate groups have lost the side digits.

EYE SOCKETS NEAR SNOUTTethytheres have eye socketsthat are located far forwards on the skull. The significance of this position is unknown,although in some forms it might have provided more space for the roots of the chewing teeth.

Woolly mammoth

The batIcaronycteris fromthe Early Eocenewas an archontan.

Cranioceras was a memberof the palaeomerycids, an extinct group of horned artiodactyls.

SYNAPSID EVOLUTIONEarly synapsids appeared during the Carboniferous andthe Permian. Their descendants, the small cynodonts of the Triassic, were the direct ancestors of the firstmammals. A diversity of primitive mammal groupsevolved during the Mesozoic, but only one of thesegroups – the monotremes – survives today. The largestand most diverse group of mammals – the placentals –evolved in the Cretaceous, and share an ancestor with the marsupials. The placentals underwent a massive burst of evolution at the start of the Cenozoic.

SYNAPSIDS CLADOGRAM

PROBOSCIDEANSAND DESMOSTYLIANS

Stapes

Hoof ofside toe

Main hoofcore

Side view of foot of extinct three-toed horse Hipparion

Skull and jaw of 20-million-year-old mastodont Gomphotherium

Eye socket

Dugong

Middle ear bones

EPITHERESStirrup-shaped

stapes

UNGULATESHoof

TETHYTHERESEyes near the front

of the skull

SOUTH AMERICANUNGULATES

Incus

SAIL-BACKED KILLERDimetrodon was one of the first big land animals to becapable of attacking and killing creatures its own size.This pelycosaur had a large, long, narrow head, withpowerful jaws and daggerlike teeth. Dimetrodon couldgrow up to 11 ft 6 in (3.5 m) in length. It survived by attacking and eatinglarge, plant-eating pelycosaurs.Dimetrodon lived during theEarly Permian in what is nowNorth America and Europe.Its remains have been foundin Texas and Oklahoma, and in Europe.

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EARLY SYNAPSIDSSYNAPSIDS (“WITH ARCH”) INCLUDE the mammal-like “reptiles” and theirdescendants, the mammals. They are named for the large hole low in the skull behind each eye. Muscles that worked the jaws passedthrough this hole, and gave synapsids a wide gape and powerful bite.Synapsids formed a separate group from true reptiles, who gave rise to lizards, dinosaurs, and their relatives. Like living reptiles, however,early kinds were scaly and cold-blooded. Synapsids appeared duringthe Carboniferous period. Early synapsids are known as pelycosaurs,and were quadrupeds with sprawling limbs. Most pelycosaurs lived in what is now North America and Europe. By early Permian times,pelycosaurs counted for seven out of ten backboned land animals.The early synapsids died out toward the end of the Permian period.


of similar shapes. Dimetrodon’s teethhad different shapes, like a mammal’s.The name Dimetrodon means “two types of teeth.” The differently shaped teethhad various functions. The pointedupper canine teeth were designed forpiercing flesh. The sharp front teethserved for biting and gripping. The small back teeth aided in chewing up chunks of flesh.

Dimetrodon skull






Dimetrodon



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EARTH LIZARDEdaphosaurus (“earth lizard”) was a large, early plant-eating pelycosaur. Its broad, short head was small for its hefty, 10-ft (3-m) long body. Its barrel-shaped body





TWO TYPES OF TEETH

Scientific name: DimetrodonSize: Up to 11 ft 6 in (3.5 m) longDiet: MeatHabitat: Semi-desertWhere found: North America and EuropeTime: Early PermianRelated genera: Haptodus, Sphenacodon

EARLY SYNAPSIDS




DINOCEPHALIAN (“terrible head”)therapsids were synapsids from thePermian whose fossils are known fromRussia, South Africa, North America,and Brazil. Their heads were massivecompared to their bodies, and thisquality gave the group its name.Dinocephalians were diverse andabundant, but they did not survive beyondthe Permian, and left no descendants.Carnivorous dinocephalians, such as thebrithopodid Titanophoneus, were long-tailed predators capable of attacking thelargest herbivores. Their large, elongateskulls held interlocking incisors – a keydinocephalian feature – and prominentcanine teeth. Herbivorous dinocephalianslacked the canine teeth of their predatory,brithopodid-like ancestors. Their enlargedtooth crowns provided a crushing surfacefor plant material, but were less suited for tearing flesh. Advanced herbivorousdinocephalians, such as Moschops, had short tails and grew to the size of rhinos.

198





HORNED HERBIVORESSeveral kinds ofherbivorous dinocephalianevolved horns or otherunusual structures on theirskulls. These may have beenused in displays or fights during the breeding season.Struthiocephalus was a long-skulled tapinocephalid fromRussia that was related toMoschops. A large bump thatprojected from its foreheadmay have once formed partof a large spike.

ESTEMMENOSUCHIDSPrimitive Russian dinocephalians calledestemmenosuchids were famous for the massivebony protuberances that grew from their cheeksand their upper skulls. These protuberances mighthave been covered in horn, and could have beenused in fights or visual displays. Some specimens of Estemmenosuchus have larger protuberances thanothers, and may be males. The canines and pointedincisors of estemmenosuchids suggest carnivoroushabits. Fossil skin impressions of Estemmenosuchusshow that these animals probably lacked scales, and may have had skin glands, like living mammals.

Horns of someEstemmenosuchusspecies were complex,with several branches.

The forehead bump may have been presentonly in males, but morespecimens are neededto confirm this theory. Wide mouth, with large

incisors and caninesthat interlocked whenthe mouth was closed.

TERRIBLE HEADS

Top view ofStruthiocephalus skull

TITANOPHONEUSThe large, Russian brithopodid Titanophoneus is known from a well-preserved skeletonwith a remarkably complete skull. Likeother predatory dinocephalians,Titanophoneus had a large, elongateskull whose interlocking teeth wereused to grab, kill, and dismemberlarge animal prey. Brithopodids had

short, powerful limbs and longtails. They bore a superficial

resemblance to earlier predatory synapsids, such as the

sphenacodontids, whose members

included Dimetrodon.

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TERRIBLE HEADS

The hind limbs were erectlike a mammal’s, unlikethe forelimbs, whichsprawled outwards.

HEAD BANGERSThickened skull bones were a feature ofdinocephalians. In tapinocephalids, suchas Moschops, the bones on the top of the

head were enlarged, and the skull was reinforced from below. This

suggests that tapinocephalidshead-butted each other, as othercreatures with thickened skullbones do. The neck vertebrae

did not meet the skull at the back of the head

– as they doin most other

animals – butjoined the skull

at its underside.This meant that

tapinocephalidsprobably walkedwith their nosespointing towards the ground.Upper arms

were verypowerfullymuscled.

ESTEMMENOSUCHUS

Scientific name: EstemmenosuchusSize: 10 ft (3 m) longDiet: Horsetails, ferns, and perhaps small animalsHabitat: Subtropical lakeside forestWhere found: RussiaTime: Mid PermianRelated genera: Jonkeria, Titanosuchus

Moschopsskeleton

Estemmenosuchus

A rounded armsocket permitteda wider range offorelimb motionthan that seen inmore primitivesynapsids.

The top of thehead was up to 4 in (10 cm)thick.

The canine teeth wereespecially large, and gaveTitanophoneus a saber-toothed appearance.

DICYNODONTS (“TWO DOG TEETH”) were short-tailed synapsids with beaked jaws who lived from the Early Permian to the Late Triassic. The unusual dicynodont jaw, combined withtheir stout, barrel-shaped bodies, suggests thatthey were herbivorous, and ate fibrous plants,such as horsetails and ferns. However, somedicynodonts may have been omnivorous orcarnivorous. Dicynodont limbs were robust,which made these creatures slow-moving, but powerful. Dicynodont forelimbs sprawledsideways, but their hind limbs were erect, like those of mammals. While most Permiandicynodonts were less than 3 ft 3 in (1 m) long,the last Triassic forms reached 10 ft (3 m) inlength and perhaps 0.9 ton (1 tonne) in weight. A superficial resemblance to hippopotamuses led dicynodonts to be regarded as amphibious.Perhaps some of them did live this way, but theymostly seem to have been residents of semi-arid,terrestrial environments.

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TWO DOG TEETH

SINOKANNEMEYERIASinokannemeyeria was a large, long-snouted, Chinesedicynodont withdownward-pointingtusks that grew frombulbous projectionson its upper jaw. Themuscle attachmentsites on the back ofthe skull were quitesmall, which suggests that Sinokannemeyeria did not have the powerful skullmuscles needed for shearing plants,unlike other dicynodonts. Mostdicynodonts chopped up food bysliding their lower jaws backwardand forward. Sinokannemeyeriafed by tearing plant material with the front of the snout. Thekannemeyeriines descended fromancestors similar to Lystrosaurus, andwere the only Triassic dicynodonts.

LYSTROSAURUSThe small, Early Triassic dicynodont Lystrosaurus had a distinctive short skull with a deep snout, high nostrils,and stout, broad limb bones. Like most dicynodonts, its jaws appear to have held a beak in life. Its powerfulforelimbs and prominent tusks could have been used fordigging. Lystrosaurus’s short yet flexible neck might haveimproved its ability to reach plant material. Its ear bonessuggest that it relied on sound vibrations conducted tothe bones from the ground, rather than through the air.

Powerful forelimbswere perhaps usedfor digging.

Its skull openingshoused large jawmuscles thatcontrolled lowerjaw movement.

Sinokannemeyeria

Devonian 416–359.2Cambrian 542–488.3 Ordovician 488.3–443.7 Silurian 443.7–416



Projections thatonce held tusks

A broad, blunt snoutallowed it to grablarge mouthfuls of plant material.

SINOKANNEMEYERIA

Scientific name: SinokannemeyeriaSize: 10 ft (3 m) longDiet: Fibrous plantsHabitat: Woodland near lakes and riversWhere found: ChinaTime: Early TriassicRelated genera: Parakannemeyeria, Rhadiodromus

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TWO DOG TEETH

The large, heavyskull was about 24 in (60 cm) long.

The feet were shortand broad withblunt claws.

Solid, wedge-shaped skullwith very broadskull roof.

BURROW DWELLERSSome small dicynodonts have features that suggestthat they dug burrows.Cistecephalus from the Late Permian of SouthAfrica had a robustskeleton with extramuscle attachments similarto those seen in modernanimals that dig. The back ofCistecephalus’s skull was modifiedfor muscles that power the head forwardduring digging. A few specimens of the SouthAfrican dicynodont Diictodon were found insidespiral-shaped burrows. Scrape marks on theburrows’ walls suggest that Diictodon used its beak or blunt claws to dig with.

TEETH AND TOOTHLESSNESSLate Permian dicynodonts had small teeth that lined

their jaws. Later dicynodonts, such as Lystrosaurus, lostthese small teeth, and retained only the large canines

in the upper jaw. In still later dicynodonts, such asSinokannemeyeria, these canines became large tusksthat differed in size between the sexes. Tusks may

have been used for fighting and display, or could havebeen used to dig with. Dicynodonts such as Oudenodon

and Stahleckeria were completely toothless.

Placerias

Cistecephalus skull



Lystrosaurus skull

Stout and broadlimb bonessuggest thatSinokannemeyeriacould not run fast.

299–251

This prominenttusk bears scratchmarks that show it was used for digging.

THE LAST DICYNODONTSBy the Late Triassic, dicynodontshad become rare. The few speciesknown from that time were largebeasts – more than 10 ft (3 m) long –and all were found in the Americas. Placerias was one of the last dicynodonts, and is known from several individuals that perished at a lake site. Sexual dimorphism (two forms of the samespecies) is evident in Placerias – in some individuals, thepointed projections that house the tusks are larger thanin others. The actual tusks were tiny in both sexes.

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DOG TEETH




CYNODONTS (“DOG TEETH”) WERE SMALL to medium-sizedcarnivorous synapsids, and were the likely ancestors ofmammals. They belonged to the theriodonts (“beastteeth”), the most advanced subgroup of those synapsidscalled therapsids. Cynodonts had a bony palate that separated the nasal passagesfrom the mouth and let them breathewhile they ate – a necessary feature of warm-blooded creatures. Othersimilarities with mammals include fewer lower-jawbones and better developed brains than reptiles, broadback teeth with ridged crowns for chewing, and adistinct chest and lower back. Cynodonts appeared inthe Permian period, but their heyday was the Triassic, when they lived worldwide. They persisted for 80million years, before dying out in the Mid Jurassic. No other group of therapsids lasted as long.

Strong, upright lowerhindlimbs helpedThrinaxodon to run fast.

TRIDENT TOOTHA low-slung, sharp-toothedcarnivore, Thrinaxodon(“trident tooth”) lived in Early Triassic South Africa andAntarctica. Thrinaxodon lived in burrows, and ate small creatures. Clues in its remainsshow that this creature was more mammal-likethan its synapsid ancestors. It had a fairly largebrain, and tiny pits in its snout that might haveheld whiskers hint that its body was hairy. Anenlarged dentary bone strengthened either side of the lower jaw and contained sockets for its teeth. Its chest and lower back regionswere probably separated by a diaphragm – a muscular sheet that contracted to fill thelungs, and would have enabled Thrinaxodonto breathe more efficiently than its ancestors.

TRIDENT TOOTH

Scientific name: ThrinaxodonSize: 19 in (50 cm)Diet: Small animalsHabitat: Open woodlandWhere found: South Africa, AntarcticaTime: Early TriassicRelated genera: Cromptodon, Tribolodon

DOG JAWCynognathus (“dog jaw”) was one of mostdangerous of Early Triassic carnivores.

At 3 ft 3 in (1 m) in length, Cynognathuswas one of the largest cynodonts.Cynognathus possessed formidable jaws – long, deep, and capable of inflicting a savagely powerful bite. Its jaws held three kinds of

teeth: small nipping incisors, great stabbing canines, and

saw-edged, shearing cheek teeth.

Cynognathus skull

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DOG TEETH

EVOLUTION OF THE JAWCynodont jaws illustrate key changes

in the evolution from early synapsid tomammal. In time, jaw bones vanishedor shrank so that the entire lower jaw

consisted of the large dentary bone.Two hinge bones gradually movedinside the skull to form two of the

mammalian middle-ear bones.Other changes produced

the mammals’ uniquechewing bite.

THREE KNOB TEETHNot all cynodonts were carnivores.Tritylodonts (“three knob teeth”) had jaws and teeth designed for eatingplants. Bienotherium had four incisorteeth, a gap instead of canines, andridged back teeth much like molars. Thegreat similarity between tritylodont andmammal skeletons suggests that mammalsoriginated from this group of cynodonts.

Thrinaxodon

Bienotherium skull

Unlike reptiles, Thrinaxodon’s ribsprotected only its chest, whichgave it a two-part body divisioninto chest and lower back.

Bienotherium gnawedtough woody plantswith its incisors, andcrushed them betweenits back teeth.

Dentary bone

Dentary bone

Skull of the cynodont Thrinaxodon

Skull of the earlysynapsid Dimetrodon

Like modern mammals,Thrinaxodon hadseven neck vertebrae.

MORGAN’S TOOTHA tiny mammaliaform (a clade with featuressimilar to mammals), Morganucodon (“Morgan’s tooth”) is often grouped with the triconodonts, extinct earlymammals named for their three-cuspedteeth. The bones of Morganucodon’s neck,chest, back, and hips were much like those of living mammals, and it stood moreupright and had a relatively bigger brainthan today’s four-legged reptiles. To avoiddinosaurs, Morganucodon probably hid inholes by day and came out to hunt at night.

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MAMMALS ARE WARM-BLOODED, backboned animalswhose females have glands that produce milkto feed their young. All mammals evolvedfrom mammal-like creatures calledtherapsids. The first mammals wereprobably Triassic shrewlike animals thatshared the same types of jawbones andmiddle ear bones as living mammals.Yet these creatures did not belong toany of the main living mammal groups– egg-laying monotremes, pouchedmarsupials, and placental mammals.Some scientists consider the first truemammal to be these groups’ commonancestor, which probably appeared in the Early or Mid Jurassic.


THE STRANGE MULTISTaeniolabis is a post-Mesozoic example of themultituberculates, a major line of rodent-like, plant-eating mammals with many-cusped teeth.They produced more than 200 known species,and varied from creatures no bigger than mice to species the size of beavers. Multituberculatespersisted for 100 million years, from the LateJurassic to the Early Tertiary, when they died out.

Morganucodon

THE FIRST MAMMALS



Sharp claws helpedMorganucodon subdueprey or dig holes in whichto hide from its enemies.

Early mammals were coveredwith hair, which suggests that this mammalian feature is primitive.

Lower jawbone of Taeniolabis

AN ANCIENT LINEThe duck-billed platypus is one of the egg-laying monotremes –the group of living mammals withthe oldest fossil record. The earliest-known monotreme fossils date from 100 million years ago, and were found in Australia. Steropodon, an early monotreme, was the size of a cat, and was quite large for a Mesozoic mammal.

The platypusdisplays the

reptilelike postureof early mammals.

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Jeholodens

THE FIRST MAMMALS

JEHOLODENSThe first complete

skeleton of a triconodont to be discoveredwas that of Jeholodens, which was found in

China in 1994. The mouse-sized, insect-eating Jeholodens had a body with a strange

mixture of features. Its forelimbs were helderect like a modern mammal’s, but its hind limbs sprawled in the fashion ofreptiles. This unusual combination offeatures hints that the various parts of

mammals’ bodies evolved at different rates.

299–251 Cretaceous 145.5–65.5 Paleogene 65.5–23


MORGAN’S TOOTH

Scientific name: MorganucodonSize: 4 in (10 cm) longDiet: Insects and wormsHabitat: ForestWhere found: Europe, Asia, North AmericaTime: Late Triassic to Early JurassicRelated genus: Megazostrodon


Jurassic 199.6–145.5Triassic 251–199.6 Neogene 23–present

Sensitive whiskersallowed Morganucodonto feel its way in the dark.

Modern duck-billedplatypus (Ornithorhynchus)

206


MANY OF THE EARLIEST MAMMALS had a pouch in their skin in which theycarried their developing babies. Most mammals later evolved a wombinside their body for the babies and slowly lost their pouch. Marsupials,however, kept this pouch, and are famous for their many Australianrepresentatives. Bandicoots, dasyuromorphs, and diprotodontians allappear as fossils in Oligocene rocks (33.9–23.03 million years ago). The bandicoots are small burrowingomnivores. Dasyuromorphs includemarsupial mice, Tasmanian devils,thylacines, and the ant-eating numbats.Diprotodontians include kangaroos, koalas, and possums.

Because of its hopping modeof locomotion, Sthenurus hasonly one main toe.

Diprotodon’s huge nose probablyhelped it breathe dry, dusty air.However, some experts suggest thatthe nose supported a small trunk.

Thylacines had sharp teeth and powerful jawsthat could be opened very wide. They werepredators of other marsupials. During thePleistocene, a wolf-sized species, Thylacinuspotens, hunted the large kangaroos anddiprotodontids of the time.




STHENURINESModern grassland kangaroos, such asthe large sthenurines, evolved in thePleistocene. Sthenurines may haveused their mobile arms to pull downbranches. The biggest sthenurines, likeSthenurus, were about 10 ft (3 m) tall.

AUSTRALIAN POUCHED MAMMALS

DIPROTODONFrom the Oligocene to the Pleistocene,Australia was populated by heavy-bodied herbivores called diprotodontids.Most diprotodontids were rather likegiant wombats. The most famous isDiprotodon, a rhinoceros-sized herbivore from the Pleistocene. Diprotodontids gradually died out during the Pleistocene as the tropical forests of Australia were replaced by grasslands. Kangaroos,which grazed on dry grasses, then became dominant.

Thylacinus

Skeleton ofSthenurustindalei

POUCHED WOLVESThe thylacines (marsupial wolves) weredoglike predators belonging to thedasyuromorph group. Thylacinus, themost recent thylacine, survived on theAustralian mainland until about3,000 years ago and on Tasmaniauntil the 1930s. The last-knownspecimen died in an Australian zoo in 1936. Thylacinus had a long,stiff tail and a very powerful bite.

Ordovician 488.3–443.7

207



Diprotodon had robustlimbs and walked onthe soles of its feet.

Studies on tooth wearshow that thylacoleonidswere predators.

Diprotodon’s hippopotamuslike bodysuggests to some experts that it wasamphibious. However, it has been foundpreserved in dry environments. Diprotodonwas the biggest ever marsupial.

Marsupials possess a pouch –a bag made of skin in whichthe baby is kept. Once born,the baby climbs into thepouch, and for this reasonbaby marsupials have powerfulgrasping forelimbs. Within thepouch the baby suckles milk.

A peculiar feature of its hind feetwas that the fifth toe was thelongest. The sharp claws couldhave been used in digging.

MARSUPIAL LIONSOne of the most remarkable marsupial groups are thethylacoleonids, also called “marsupial lions.” Because of its catlikeskull and teeth, Thylacoleo (the first thylacoleonid to be discovered)was first interpreted as a carnivorous predator. Later on, someexperts argued that it was more likely a fruit-eater. However, furtherstudies showed without doubt that it was a predator. Its limbssuggest that it was an able climber and perhaps stalked preythrough the trees, jumping onto them from above.

AUSTRALIAN POUCHED MAMMALS

DIPROTODON

Scientific name: DiprotodonSize: 10 ft (3 m) longDiet: Shrubs and bushesHabitat: Scrubland, open woodlandWhere found: AustraliaTime: Late Neogene (Pleistocene)Related genera: Euowenia, Stenomerus,Nototherium

Thylacoleo skull

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AMERICAN MARSUPIALS (POUCHED MAMMALS), a groupcalled the Ameridelphia, evolved in North Americaduring the Late Cretaceous but underwent most oftheir evolution in South America. Here they diversifiedinto a major group of predatory species called theborhyaenoids. These included dog- and bearlike forms,and a species that resembled saber-toothed cats.Opossums are one of the most successful Americanmarsupial groups and also moved into Europe, Africa,and Asia. These, and a poorly known separate groupcalled the shrew opossums, are the only Americanmarsupials to survive today. American marsupials neverevolved the diversity of the Australian marsupials.




THE BORHYAENOIDSBorhyaenoids were predatory American marsupials known throughmost of the Cenozoic Era. Early forms, such as Mayulestes, wererather like opossums. Some, like Cladosictis, were about 3 ft (1 m)long and resembled modern martens. Others, like Borhyaena, weregiant predators as big as lions or large bears. Lycopsis was aborhyaenoid of the Miocene related to Borhyaena and Thylacosmilus.

AMERICAN OPOSSUMSAlphadon, from the Late Cretaceous ofNorth America, is one of the earliestknown opossums. About 66 species ofopossum are known today from acrossSouth America, Mexico, and the US. Theyare mostly long-tailed climbing marsupialsthat vaguely resemble rats or weasels.

AMERICAN POUCHED MAMMALS

THYLACOSMILUSOne of the most remarkablemarsupials was Thylacosmilus, asaber-toothed borhyaenoid thatsuperficially resembled saber-toothed cats. Thylacosmilus wasroughly the same shape andsize as a big cat, but in thedetails of its skeleton it isclearly very different and morelike a giant opossum. Unlikecats and other carnivores, thesaber-teeth of Thylacosmilusnever stopped growing andalways had to be worn down attheir tips. The roots of the teetharced upward over the front of the skull, growing above the eyes.

Alphadon

Lycopsis skeleton

The shape of its body suggeststhat Thylacosmilus jumped out atits prey from the cover of bushesor tall grass. Perhaps it wascolored like a living lion, ormaybe it had stripes.

209



POUCHED HOPPERSThe argyrolagids were mouse-sized Americanmarsupials that lived from 34 to 2 million yearsago, from the Eocene to the Pliocene. They hadvery long hind limbs and small forelimbs and thusappear to have moved by hopping, just likekangaroos or jerboas. Argyrolagus from Patagoniais the best-knownargyrolagid. At times ithas been argued thatargyrolagids are notmarsupials, but it nowseems that they arepart of the Americanmarsupial group thatalso includes the shrew opossums.

AMERICAN POUCHED MAMMALS

Unlike true cats, Thylacosmiluslacked retractile claws. Even so,its limbs were powerful andcapable of grasping. It probablypulled its prey to the ground.

Large protective flanges grew down-ward from the chin. Thylacosmilusmight have used these to help guideits saber-teeth into the body of itsprey. The flanges would also haveprotected the teeth from damagewhen the jaws were closed.

Massive muscles atthe back of the skullwould have givenThylacosmilus apowerful bite.

Like saber-toothedcats, Thylacosmilushad a flexible,powerful neck.

Argyrolagus

THYLACOSMILUS

Scientific name: ThylacosmilusSize: 1.3 m (4 ft) longDiet: Probably hoofed mammals and marsupialsHabitat: Grasslands, open woodlandsWhere found: ArgentinaTime: Late Neogene (Miocene–Pliocene)Related genera: Paraborhyaena, Anachlysictis

210210

A BIZARRE GROUP OF AMERICAN MAMMALS called the xenarthrans are probablythe most primitive members of the placental group (mammals that carrytheir young with the aid of an organ called a placenta). The namexenarthran means “strange joints” and refers to the peculiar extra jointsthese mammals have between their vertebrae. Sloths, anteaters, andarmadillos are the living representatives of xenarthrans. Some xenarthrans,such as anteaters, have no teeth, and in the past the group was calledEdentata, meaning “the toothless ones.” However, most xenarthrans do have teeth – large ones in sloths and the tanklike glyptodonts.Xenarthrans were important herbivores and insectivores in SouthAmerica. Some types migrated into North America in the Late Pliocene.

Glossotherium hadmassive hips and veryrobust limbs.

Ground sloth fur isknown for somePleistocenespecies. It wasshaggy and brown.

Ground sloths had astout, powerful tailthat they probablyused as a prop whenthey reared up on theirback legs.


MEGATHERIUMUntil relatively recently, there were sloths thatlived on the ground and grew to be as big as amodern elephant. These were the groundsloths and, rather than climbing onbranches to eat leaves, they reached upwith powerful arms and claws to pullbranches down toward their mouths.The very biggest ground sloths, suchas Eremotherium and Megatherium,were huge, reaching 20 ft (6 m)in length and weighing about3 tons. Living sloths are all tree-climbing animals that hangupside down and are no biggerthan a medium-sized dog.

GLOSSOTHERIUM A medium-sized sloth called Glossotherium livedduring the Miocene, Pliocene, and Pleistocenein South and North America. Like most sloths,it lived in wooded grasslands and forests. Somesloths inhabited different environments.Thalassocnus lived on the beaches of Peruand may have swum in shallow water to eat

seaweed. Dwarf ground sloths less than 3 ft (1 m) long lived on the Caribbean islands.

STRANGE-JOINTED MAMMALS



211211

Paleogene 65.5–23 Neogene 23–present


All ground sloths, likeliving tree sloths, hadlarge, curving clawson their fingers.These were probablyused as hooks to pulldown branches butcould also have beenused in self-defense.

Megatheriumhad five fingers,but some otherground slothslacked thethumb, whileothers lackedthe first twofingers.

Someglyptodonts hada tail that couldbe used as aweapon.

Deep short skullwith massivechewing teeth

The feet have large clawswhich curve inward.Fossil tracks show thatground sloths sometimeswalked on two legs.

GLYPTODONT ARMORThe bodies of glyptodontswere covered by a rigid shellof interlocking hexagonalscales (scutes). Rings of scutesalso covered the tail andsometimes over the top of the skull. Some glyptodontspecimens have fractured shells,suggesting that they battledone another with their tails.

MAMMALIAN TANKSGlyptodonts were armored

xenarthrans something like giantarmadillos, known principally from South

America. The smallest glyptodonts wereabout the same size as living armadillos, butthe largest kinds, like Doedicurus, Hoplophorus,and Panochthus, were more than a ton inweight and about 10 ft (3 m) long.

STRANGE-JOINTED MAMMALS

Panochthus

MEGATHERIUM

Scientific name: MegatheriumSize: 20 ft (6 m) long Diet: Leaves and twigsHabitat: Wooded grasslandWhere found: South AmericaTime: Late Neogene (Pliocene–Pleistocene)Related genera: Pyramiodontherium, Ocnopus, Eremotherium

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5


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PLACENTALS, THE GROUP OF MAMMALS whose young develop insidetheir bodies, arose in the Late Cretaceous. The earliest were small,

nocturnal omnivores (meat- and planteaters) that resembled livingshrews. Nearly all living mammals are classed as placentals, except forthe monotremes, which lay eggs, and the marsupials, whose youngdevelop for a short time inside their bodies and are then carried in apouch. Many primitive placental mammals have marsupial-like pouchbones, but this does not necessarily mean that they all had pouches.The placentals evolved rapidly at the end of the Cretaceous, when thedinosaurs were becoming extinct. Pantodonts and tillodonts, whichlived in the Paleocene (65.5–55.8 million years ago), were the firstplacentals to grow larger than the size of a living badger.

The brain ofZalambdalestes wasabout three-quartersthe size of the brainof a living shrew.




PLACENTAL PIONEERS

ZALAMBDALESTES

Scientific name: ZalambdalestesSize: 8 in (20 cm) longDiet: Insects and other small animalsHabitat: Scrubland and desertWhere found: MongoliaTime: Late Cretaceous Related species: Alymlestes, Barunlestes

Below its long snout, Zalambdalesteshad long incisor teeth. There was agap between the incisors and theteeth at the back of the jaws.

ZALAMBDALESTESOne of the best-known early placentals was Zalambdalestesfrom Late Cretaceous Mongolia. It was a long-snouted,four-legged mammal whose slim forelimbs were longerthan its hind limbs. It probably looked much like the livingelephant-shrews, a group of small, long-legged, omnivorousmammals with mobile snouts. They run fast and leap toescape predators. Some experts believe that Zalambdalestesis closely related to elephant-shrews. Other experts arguethat Zalambdalestes is the earliest lagomorph, which is agroup that includes rabbits and their relatives.

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PLACENTAL PIONEERS

TILLODONTSThe tillodonts were agroup of Paleocene andEocene placentals that

lived in Asia, NorthAmerica, and Europe. Theyhad clawed feet and largegnawing teeth, and probablyfed on roots and tubers.Trogosus was one of the

biggest tillodonts and grew tothe size of a bear. The tillodonts maybe related to pantodonts, and bothgroups may be distant relatives of thecarnivore group, though this iscontroversial.

UKHAATHERIUM AND RELATIVESThe asioryctitheres were Mongolian

Cretaceous placentals that superficiallyresembled living shrews and other members of

the insectivore group. Features of their skulland hip bones show that, despite this

resemblance, asioryctitheres were not relatedto insectivores and they lack advanced featuresseen in the later groups of placental mammals.The asioryctithere Ukhaatherium is known from

beautifully preserved, complete skeletons.It was a tiny animal – the complete

skeleton is only about 4 in (10 cm) long.

Like many other early placentals,Zalambdalestes had bones near itships that may have supported a pouchor may have helped to support theside wall of the abdomen. Most of thelater placentals lost these bones,whereas the marsupials kept theirs.

Ukhaatherium’s small andpointed teeth were suitedto eating insects.

Ukhaatherium fossil

Coryphodon

Trogosus skull

PANTODONTSThe pantodonts were bulky placental

mammals that thrived in the Paleocene andEocene (65.5–33.9 million years ago), althoughthey left no descendants. Their feet were tippedwith nails or claws, and males had large canineteeth perhaps used for fighting. Their cheek teethshow that they were herbivores (planteaters).Coryphodon was a widespread northern hemispherepantodont the size of a hippopotamus, but its brainwas the smallest of any mammal.

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CARNIVORANS – CATS, HYENAS, dogs, bears, and all of their relatives –are one of the most successful groups of mammals. Their key featureis their specialized shearing teeth, called carnassials. While manyother mammals have carnivorous (meat-eating) habits and some evenhave carnassials, in true carnivoransthese teeth are uniquely formedfrom the fourth upper premolarand the first lower molar. A uniquecharacter of primitive carnivorans istheir retractile claws, which can bepulled back into protective sheaths.Carnivorans have a fossil record fromthe Paleogene. They evolved in northerncontinents from among the “miacoids” –meat-eaters of mixed ancestry.

LIFE IN THE TREES

The limb skeletons of some“miacoids”, such as Vulpavus

from Eocene North America, showthat these animals had highly mobile

limbs like those of modern carnivorans thatregularly climb in trees. Vulpavus also has

sharply curved claws, which supports this idea.However, a climbing lifestyle was probably not true

of all “miacoids.” Didymictis, from Paleocene-Eocene North America and Europe, probably lived

at ground level and may have been a fast runner or a digger.

Its wrist, elbow, and shoulderjoints show that Vulpavushad flexible, powerful limbsand would have been anagile climber.

The retractile claws ofprimitive carnivoranswere used in climbingand holding prey. Theywould have beenpermanently needle-sharp.


MIACISOne of the best-known “miacoids” was Miacis, an early member of the dog-branch group ofcarnivorans. Like many other early carnivorans,Miacis was well suited for a climbing lifestyle andhad limbs and joints that resemble those ofmodern climbing carnivorans. Miacis was probablyan agile predator that hunted small animals andmight also have eaten eggs and fruit.

EARLY CARNIVORANS“Miacoids” had smallerbrains for their body sizethan modern carnivorans.Also, their binocular visionwas not as good as that ofmodern carnivorans.



Vulpavusskeleton

Cambrian 542–488.3 Ordovician 488.3–443.7 Silurian 443.7–416 Devonian 416–359.2


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Early carnivorans such as Miacishave five toes on both theirhands and feet. Latercarnivorans have four toes onthe foot.

EARLY CARNIVORES

MIACIS

Scientific name: MiacisSize: 1 ft (30 cm) longDiet: Small mammals, reptiles, birdsHabitat: Tropical forestsWhere found: Europe and North AmericaTime: Paleogene (Paleocene–Eocene)Related genera: Chailicyon, Vulpavus, Oodectes

Hyaenodon skull

“Miacoids” may have used their tails asbalancing aids and as rudders that helpeddirect them when leaping from tree totree. Modern climbing carnivorans usetheir long tails in this way.

CREODONTSHyaenodon was a wolflike animal with carnivorous habits. It is part of a group calledthe creodonts, which are not regarded astrue carnivorans. Living from Paleocene toMiocene times, creodonts would haveresembled modern civets, cats, or dogs.Slicing teeth at the back of the jaws show thatall were committed to a predatory lifestyle.



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FELIFORMS, including cats,emerged during the Eocene(55.8–33.9 million years ago).While some feliforms becamelarge predators in open environments, others retained the forest-dwellinglifestyle and long-bodied shape of the ancestralmiacoids. Civets and genets, properly calledviverrids, are primitive feliforms that have remainedlargely unchanged. Viverrids may include theancestors of hyenas and mongooses, which both firstappeared in the Oligocene (33.9–23 million yearsago). Cats are short-skulled feliforms that are morespecialized for eating meat than virtually any othermammal. The earliest cats appeared in theOligocene of Europe, and saber-toothed cats evolvedearly in the Miocene (23–5.3 million years ago).




ENLARGED CANINESAs cats evolved, they enlarged theircanines for biting and their carnassialsfor slicing but reduced or lost theirpremolar and molar teeth. The saber-toothed cats enlarged their canines toan extreme. With these specialized teeth,cats administer either a suffocating bite tothe neck or sever the spinal cord of a preyanimal that they have caught.

HYENASThough modern hyenas may appearto resemble dogs more than cats,

hyenas belong to the cat group ofcarnivores. Skeletal features show

that early hyenas were similar tocivets and genets. These bone-

crushing hyenas evolved in theMiocene and spread throughout

Africa, Asia, and Europe. Earlyhyenas, such as Ictitherium, were much smaller than living hyenas.

TERRIBLE CATSome fossil cats, such as Dinofelis (“terrible cat”)from the Pliocene and Pleistocene, had enlargedcanine teeth halfway in between the conicalstabbing canines of modern cats and the flattenedblades of saber-tooths. As a result Dinofelis has beencalled a “false saber-tooth”. However, other skeletalfeatures of Dinofelis and its relatives, a group called the metailurines, show that they should probably beclassified as true members of the saber-toothed group.Dinofelis had body proportions like those of modernforest-dwelling cats such as leopards and jaguars, andit was about the same size as these species.

The giantcanines ofsaber-toothedcats are oval-shaped incross-sectionand can haveserratedmargins.

Ictitherium skull

Smilodonskull

CATS AND OTHER FELIFORMS

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CATS AND OTHER FELIFORMS

If Dinofelis was aninhabitant of forests andwoods, it probably had aspotted coat like livingforest-dwelling cats.

Dinofelis had limb proportionsbetter suited for strength thanspeed, as was true of nearly allsaber-tooths. It may have been apowerful and able climber, likemodern leopards and jaguars.

All cats have shortened,rounded skulls. Their eyesface forward and providethem with an overlappingfield of vision which allowsthem to accurately judgedistances.

As well as having remarkablecanines, saber-toothed cats alsohad unusualprotrudingincisors.

PrehistoricSmilodoncompared withmodern tiger

MODERN CAT COMPARISONSMost saber-toothed cats were large, and the biggest forms, including Smilodon andHomotherium from the Pliocene and Pleistocene,were larger than the biggest living lions andtigers. Because of their dependence on largeprey animals, these cats were vulnerable toextinction when their prey became rare. Unlikesaber-toothed cats, the modern cat group, theFelinae, includes both large and small species.

Scientific name: DinofelisSize: 2.2 m (7 ft) longDiet: Deer, antelopes, apes, other mammalsHabitat: WoodlandsWhere found: Europe, Asia, Africa, North AmericaTime: Late Neogene (Pliocene–Pleistocene)Related genera: Metailurus, Adelphailurus

TERRIBLE CAT



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THE MACHAIRODONTINES, otherwise known as saber-toothed cats, wereprehistoric members of the cat family and famous for their massivecanine teeth. They probably descended from the primitive catPseudaelurus of the Miocene (23–5.3 million years ago). During thePliocene and Pleistocene (from 5.3 million years ago), they diversifiedinto American, African, European, and Asian species ranging in sizefrom that of a modern puma to that of a lion. The very last saber-toothed cats died out as recently as 10,000 years ago. The most famousis Smilodon, a genus known from both North and South America.

SABER-TOOTHED CATSSmilodon had immenselypowerful arms andshoulders, and an especiallypowerful and flexible neck.These characteristicssuggest that Smilodonfrequently grappled largestruggling prey to theground before delivering a killing bite to the neck.



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SABER-TOOTHED CATS

HUNTING AND SCAVENGING TOGETHERMore carnivore species lived alongside one another in thePleistocene than they do today, so fighting and competitionwere probably more severe. Many Smilodon specimens showinjuries and deformities from hunting and fighting. Somespecimens survived major injuries, such as broken hips andjaws. While these injuries were healing, these cats would havebeen unable to hunt. Perhaps, therefore, Smilodon lived in socialgroups. Injured individuals would have been able to scavengefrom kills made by other group members.

SMILODON

Scientific name: SmilodonSize: 5-8 ft (1.7-2.5 m) longDiet: Large mammals including horses,ground sloths, bison, and camelsHabitat: GrasslandsWhere found: North and South AmericaTime: Late Neogene (Pliocene–Pleistocene)Related genera: Megantereon, Paramachairodus

In the largest examples of Smilodon,the upper canines were more than10 in (25 cm) long. These teeth wereactually quite fragile and were likelyto break if twisted or if they madecontact with bone.

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CANIFORMS, A GROUP THAT INCLUDES dogs, bears, and seals, evolved in the Eocene (55.8–33.9 million years ago). Dogs were the earliestcaniforms to appear and, until the end of the Miocene (5.3 millionyears ago), were uniquely North American. The earliest dogs, such asHesperocyon, have both tree-climbing and ground-dwelling character-istics, while some later dogs became catlike predators with shortenedskulls and grasping forelimbs. New types of caniform including weasels,raccoons, and bears evolved late in the Eocene. Many became smallclimbing omnivores (meat- and plant-eaters), others became herbivores(plant-eaters) or miniature undergroundpredators. Others took to life in the water. Bear-dogs lived from the Eocene to the Miocene.

Canis dirus had aproportionally wider head,stronger jaws, and largerteeth than living wolves.These meant that it wasbetter than modern dogs atbreaking and eating bones.

As in most carnivores, dogshave collarbones that aresmall slivers of bonesupported by ligaments.This allows a wider swing ofthe forelimbs, an advantagein running predators.




HYENALIKE DOGSBorophagines were an important group of North American dogs that lived from the Oligocene (33.7 million years ago) to thePleistocene (10,000 years ago). They are bestknown for Osteoborus, a wolf-sized form with ashortened skull and enlarged crushing molars.Some borophagines were as big as modern lions.Osteoborus probably led a hyenalike lifestyle but this was not true of all borophagines – someresembled raccoons or coyotes and might have been omnivorous.

DOGS AND OTHER CANIFORMS

DIRE WOLFCanis dirus (“the dire wolf”) was a large wolf from NorthAmerica in the Pleistocene and one of the most famousfossil dogs. Its fossils are best known from the RanchoLa Brea tar pits in California where more than 1,600dire wolves are preserved. It is thought that these wolveswent to feed on animals trapped in the tar and thenbecame trapped themselves. Compared with modernwolves, dire wolves had proportionally larger skulls and teeth, but shorter legs.

Osteoborus skull

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BEARSThe eight living bearsbelong to a group ofbears called theursines. Mostursines are flat-footedomnivores. Some, like thegiant pandas and Ursus spelaeus, ofthe Pleistocene, became cave bears.Extinct bears include the running,doglike hemicyonines, the raccoon-like amphicynodontines, and theswimming bear Kolponomos.

DOGS AND OTHER CANIFORMS

DIRE WOLF

Scientific name: Canis dirusSize: 6 ft 6 in (2 m) longDiet: Large mammals and other animals,carrion, possibly fruit and nutsHabitat: Grasslands and woodlandsWhere found: North America and northernSouth AmericaTime: Late Neogene (Pleistocene) Related species: Canis lupus, Canis etruscus

SEALS AND SEALIONSSeals, sealions, and walruses evolved from bearlike ancestors in the Oligocene (33.9–23 million years ago).Early types resembled otters but possessed

flipperlike hands and feet, and enlargedeyes that helped them to see better in thewater. By the late Miocene, seals had spreadacross the world, while walruses and sealions

such as Thalassoleon had evolved in the northern hemisphere.

As with other modern types of dogs,the Dire wolf’s hands and feet werespecialized for running. It walked onlyon its fingers and toes, and its bluntclaws could not be retracted.

The tail is animportant socialsignal in livingdogs andprobably was in all prehistoricdogs as well.

Thalassoleon mexicanus skull

Skeleton ofUrsus spelaeus



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ICARONYCTERISFossil bats such as Icaronycteris probably hunted atnight, using their high-pitched calls and sensitivehearing to detect flying insects. They were likely to have hunted in places where insects gather atnight, such as lakesides and the tops of trees. Theshape of its wings suggests that Icaronycteris flew incluttered environments such as forests, rather thanover open grasslands. Some experts suggest thatbats took to hunting at night to avoid thepredatory birds that were evolving.



223

INSECTIVORES AND BATS



224

MOLES, HEDGEHOGS, SHREWS, and other insectivores (also calledlipotyphlans) are known from the Eocene and share distinctivesnout muscles and skull bones. Primitive relatives ofshrews, Batodon and Otlestes, are known from the LateCretaceous. Bats, the second most species-rich groupof living mammals after rodents, share features withprimates, colugos, and tree shrews, and areunited with them in a group called theArchonta. Like pterosaurs and birds, bats evolved true flapping flight and havemodified forelimbs in which the fingerssupport skin membranes that reach the ankles.Even the very earliest Eocene bats had fullydeveloped wings and were accomplished flyingpredators that used sonar to detect insects.


A LIFE UNDERGROUND OR IN THE WATERPrehistoric moles resembled shrews and were lessgood at burrowing than modern moles, whichevolved to be more specialized for life under-ground than any other mammal. Molesrely on smell and touch and are able to detect the electrical signals madeby the muscles of their prey.Desmans are swimming molesthat evolved in the Oligocene(33.7–23.5 million years ago) and survive today.


ICARONYCTERISThe early bat Icaronycteris is known from Eocene North America.Other Eocene bats are known from Africa, Australia, andEurope. Their ear bones show that they were able to hear high-frequency sounds. Like modern bats, Icaronycterisprobably used sonar – after making a high-pitched noise,the bat listens to the echoes and can use these to detectthe presence and whereabouts of nearby objects.

Modern desmans have a flexible,sensitive snout. As with mostinsectivores, their sharp, pointed toothcusps allow them to catch and chewworms, insects, snails, fish, and frogs.

The wing membranes of all bats are made upof layers of skin. Smallmuscles help controlthese membranes.Though the membranesare thin, they repairquickly if torn.

Lower jaw bone of Desmana moschata

Icaronycteris hadsharp-clawed feet that could be turnedbackward, allowing itto hang upside down.

Unlike modern microbats, earlyforms such as Icaronycteris hadclaws on their second fingers as well as on their thumbs.



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SPINY AND HAIRY HEDGEHOGSModern hedgehogs are split into two groups. True hedgehogs are spiny and short-tailed, while moonrats are furry and long-tailed.However, hedgehogs have a rich fossil record and numerous typesare known. Some types were tiny and shrewlike, while Miocenemoonrat Deinogalerix was nearly 3 ft (1 m) long. Macrocranionwas a primitive Eocene hedgehog known from Europe and NorthAmerica. It had a long tail and probably lacked spines. A closerelative, Pholidocercus, had an unusual fleshy gland on its forehead.

FRUIT EATERS,VAMPIRES, AND FISHERMENBefore the Eocene, bats split intotheir two main groups, the mostlyinsect-eating microbats and themostly fruit-eating megabats.Fish-eating bats evolved in theMiocene (23.5–5.3 million yearsago) and survive today. TheAmerican fruit- and pollen-eatingmicrobats include horseshoe batsand the vampire bats that feed onthe blood of mammals and birds.


ICARONYCTERIS

Scientific name: IcaronycterisSize: 15 in (40 cm) wingspan, 6 in (15 cm) body lengthDiet: Flying insectsHabitat: Forests, caves, riverbanksWhere found: North AmericaTime: Early Paleogene (Eocene)Related genera: Archaeonycteris, Palaeochiropteryx

Bats have large earsand acute hearing.

Icaronycteris had moreteeth than moderninsect-eating bats.

Long, thin fingers supportwing membranes.

Macrocranion fossil

Livinghorseshoe bat

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LEMURS LARGE AND SMALL

Lemurs probably evolvedfrom adapids some time

in the Miocene or earlier.Prehistoric lemurs were more

diverse than they are today.They included gigantic

climbing forms, ground-dwellingmonkeylike forms, and long-

armed forms that probablyclimbed upside-down like tree

sloths. Megaladapis was a massivekoalalike lemur with a long skulland huge molar teeth. Aslarge as the living orang-utan, it died out only600 years ago.

PRIMITIVE PRIMATESPRIMATES ARE CHARACTERIZED by their grasping hands and feet,large brains, and eyes with an overlapping field of vision. Thegroup includes primitive forms, such as lemurs, and advancedforms such as apes and humans. Primatelike mammals,such as Purgatorius from North America, appeared earlyin the Paleocene, but whether these animals are trueprimates or not is controversial. Some true primates ofthe Paleocene and Eocene resembled lemurs while otherswere like tree shrews. Lemurs, dwarf lemurs, and lorises are the only survivors of the more primitive primate groups.Another important early primate group was the lemurlikeadapids, a group known from the Eocene, Oligocene, andMiocene of Africa, Europe, Asia, and North America.

The longplesiadapid skullwas unlike that of later primates.

Megaladapis had a dog-like head and mighthave been responsiblefor ancient legends of“dog-faced men.”

Like other primitive primates,but unlike monkeys and apes,plesiadapids had claws on theirfingers and toes, not nails.

PLESIADAPISThe plesiadapids were an early primategroup, best known for Plesiadapis from the Paleocene and Eocene of NorthAmerica and Europe. Plesiadapis hadgrasping fingers and toes, and a long tail. It probably looked something like a crossbetween a lemur and a squirrel. Like a number of other early primates, theplesiadapids had prominent incisor teeththat resemble those of rodents. Perhapsthey chewed at wood to extractgrubs, or to get at sap.



Megaladapis edwardisskeleton

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LONG FINGER EVOLUTIONAye-ayes (daubentoniids) are a Madagascan group of primatesthat may be more primitive than lemurs. The living aye-aye

(Daubentonia madagascariensis) has a remarkable long third finger, which

it uses to extract grubs out of holes intrees. Some other mammals, such as the

apatemyids from the Paleocene, Eocene, andOligocene, evolved similar fingers. These fine-fingered mammals seem to have played therole that woodpeckers did elsewhere.

Paleogene 65.5–23


PRIMITIVE PRIMATES

PLESIADAPIS

Scientific name: PlesiadapisSize: 30 in (80 cm) longDiet: Insects, fruitHabitat: Subtropical forestsWhere found: Western North America, EuropeTime: Early Paleogene (Paleocene–Eocene)Related genera: Platychoerops, Nannodectes

NOTHARCTUS One of North America’s last native primates

was an Eocene adapid called Notharctus.Named in 1870, it was also the first North

American fossil primate to be recognized.Thanks in part to the chance discoveryof new specimens during the 1980s,

Notharctus is now one of the best-knownearly primates. Like other adapids,

Notharctus had long fingers, thumbs, andtoes, and could grip objects powerfully.

With its long limbs, flexible back, long tail,and short skull, Notharctus would have

resembled the agile leaping lemurs of today.

Like squirrels, Plesiadapis could have used its tail for balance whenclimbing and jumping. The tail mayalso have been boldly patterned.

Longfinger

Living aye-aye

299–251 Cretaceous 145.5–65.5 Neogene 23–present


Triassic 251–199.6 Jurassic 199.6–145.5

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MONKEYS ARE PART OF A GROUP OF PRIMATES called theanthropoidea, which descended in the Eocene (53–33.7million years ago) from ancestors related to the livingtarsiers of eastern Asia. The teeth of anthropoids aredistinguished by enlarged canines, flattened molars,and molar-like premolars. These features and othersallowed anthropoids to become better at foraging forfood at ground level than other primates. There aretwo main types of monkeys. The Old World monkeyscame to dominate the “Old World” of Africa and Asia.These monkeys share an ancestor with apes and arecalled the catarrhines (so-named for their downward-pointing nostrils). The New World monkeys, which are also called the platyrrhines (from their flat noses),evolved in the “New World” of South America.

THEROPITHECUS OSWALDIOld World monkeys invaded grassland environments toexploit grasses and other sources of food. Various species of Theropithecus, a seed-eating grassland monkey, evolved in the Pliocene and lived across Europe, Africa, and Asia.Theropithecus oswaldi was the largest species and considerablybigger than its living relative, the gelada of Ethiopia.

Theropithecus, like other anthropoids,has an opposable thumb that can beused for delicate handling of objects.


AMERICAN INVASIONIn the past experts argued over whetherplatyrrhines descended from unknown

North American ancestors, or if theyhad crossed the Atlantic Oceanfrom Africa (shown on the diagramby the red arrow). During storms,small animals can be washed out to sea on huge floating masses of

vegetation, which may then becarried to another land by currents.

New fossils show that platyrrhines havean African ancestor that reached South

America during the Eocene (53–33.7 millionyears ago) or Oligocene (33.7–23.5 million yearsago). At that time the Atlantic Ocean was not as wide as it is today, but it would still have beendifficult to cross.

The Old Worldincluded Africa,Europe, and Asia.



Outline of continentsas they are today

MONKEYS

The New Worldincluded South andNorth America.

NewWorld

OldWorld

ATLANTICOCEAN

Shape and position ofcontinents in the Eocene

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OLD WORLD MONKEY EMPIREOld World monkeys, many of them agile tree-climbers,replaced monkey-like apes during the Miocene (23.5–5.3million years ago). One group, the colobids, migrated outof Africa in the Miocene and evolved in Asia into the leaf-eating langurs and proboscis monkeys. Mesopithecus andParacolobus were early colobids that probably resembled the living langurs. The colobids have massive, complexstomachs and guts for digesting tough plant foods. Someforms are well adapted for life in the trees. The best-knownOld World monkey lineages, such as baboons, mangabeys,and guenons, evolved in the Pliocene (5.3–1.8 millionyears ago) in Africa.

FOREST-DWELLING NEW WORLD MONKEYSUnlike Old World monkeys, the New Worldmonkeys never seem to have taken to grasslandlife and have remained animals of the forests.The earliest known South American monkey isBranisella from the Early Oligocene (33.9 millionyears ago) of Bolivia. Tremacebus, from the LateOligocene (23 million years ago) of Patagonia,resembled the living owl monkey. Two giantrelatives of spider monkeys, Protopithecus andCaipora, lived in Pleistocene Brazil (1.81 million–10,000 years ago).

Unlike earlier primates,anthropoids have nails onall their fingers and toesrather than claws. Nailsallow the presence ofsensitive pads on the tipsof the digits, something notpossible if claws cover theends of the digits.

Paracolobus skeleton

MONKEYS

THEROPITHECUS

Old World monkeys like Theropithecus use theirtails for display and for balance when climbing,but they cannot use the tail to grasp things with. New World monkeys are characterized byprehensile (grasping) tails that are used to holdon to branches when climbing.

Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Palaeogene 65.5–23 Neogene 23–present


Upper skull of Tremacebus

Scientific name: TheropithecusSize: 3–6 ft (1–2 m) longDiet: Grasses, seeds, fruit, and invertebratesHabitat: GrasslandsWhere found: Africa, Europe, southern AsiaTime: Late Neogene (Pliocene onwards)Related genera: Gorgopithecus, Parapapio, Papio

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THE GROUP OF AFRICAN APES that includes the ancestors ofmodern humans were first recognised in 1925. The groupis called the australopithecines and contains about tenspecies of apes. Controversy continues over exactly whichspecies the group should include, their lifestyles, andappearances. It was once thought that the various australo-pithecine species became more human-like over time, butthis idea now seems too simplistic. Studies have shown thatsome of the earlier species were proportioned in a similarway to modern humans, while some of the later specieswere more chimp-like. Some had human-like skulls butchimp-like bodies. It also seems that some walked on their knuckles in the same way as living chimps andgorillas, while others walked upright like humans.




AUSTRALOPITHECINES

AUSTRALOPITHECUSAFARENSISA skeleton from Hadar,Ethiopia, represents the best-known australopithecine species,Australopithecus afarensis. This famous specimen, which is about 40%complete, was originally thought to befemale and was popularly called “Lucy”.However, many experts now believe that“Lucy” was in fact male and so call theskeleton “Lucifer”. Australopithecusafarensis was small – only 3 ft 3 in (1 m)tall. Its limbs were proportioned muchlike the limbs of modern humans.Anatomical details of the hips and limbsof “Lucy” suggest that Australopithecusafarensis could walk on two legs. It lived4–2.9 million years ago.

THE TAUNG CHILDThe first australopithecine specimen to bediscovered was the skull of a child from Taung,South Africa. This was the species later namedAustralopithecus africanus (“southern ape from Africa”).Curiously, the so-called Taung child was foundamong the fossilized partial remains of numerousmedium-sized mammals. On these bones weredistinctive nicks like those made by the beak of aneagle. Fragments of an egg shell from a large birdwere also found. It therefore seems that a large eaglehad fed on, and perhaps killed, the Taung child.

Most australopithecines had a brainsize of 25–30 cu in (400–500 cc).This is intermediate between that of chimps and early Homo species.

Compared tomodern humans,australopithecineshad enlargedchewing teeth.

Preserved australopithecinefootprints show that, as inmodern humans, the big toe was parallel with others.

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ROBUST AUSTRALOPITHECINESSeveral australopithecine species,

including Australopithecus robustus,Australopithecus aethiopicus, and Australo-pithecus boisei, are characterized by deep,massive jaws, robust skulls, and enlargedmolar teeth with thickened layers of

enamel. Some experts believe that these species should be united in the

genus Paranthropus – the so-called “robustaustralopithecines”. Others argue that thesespecies do not share the same ancestor.

AUSTRALOPITHECUS HABILISThis species was originally named Homo habilisand was thought to be the most primitive Homospecies. The name Homo habilis means “handyman” – abundant stone tools found with fossilssuggest that it was adept at making and usingcutting and scraping tools. Laterdiscoveries show, surprisingly, that the species had ape-likeproportions with long arms andshort legs. It may therefore havebeen less human-like than the oldmodel shown here. Some experts think that Homo habilis is actually a type ofAustralopithecus and would rename it Australopithecus habilis.

The finger bones are curved,unlike the straight bones ofmodern humans.

The jaw muscleswere large and ape-like. They ate a lot of tough plant food.

Though its hips andlegs suggest that itcould walk bipedally,Australopithecusafarensis was probablyalso an able climber.

The molar teethhave thickenedlayers of enamel.

Lower jaw ofAustralopithecusboisei

AUSTRALOPITHECINES

AUSTRALOPITHECUS AFARENSIS

Scientific name: Australopithecus afarensisSize: 3 ft 3 in (1 m) tallDiet: Leaves, fruit, tubers, carrion, animalsHabitat: Open woodland, wooded grasslandWhere found: Eastern AfricaTime: Late Neogene (Pliocene)Related species: Australopithecus anamensis,Australopithecus africanus, Australopithecus garhi

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HUMANS BELONG TO A GENUS OF HOMINID CALLED HOMO, which probably evolvedfrom an advanced species of Australopithecus apes. One of the most primitivemembers of the Homo genus is the famous Homo erectus (“upright person”) fromsouthern Asia and elsewhere. Homo erectus was a very successful hominid andlived alongside our own species for thousands of years. Fossils of Homo erectusranging from nearly two million to perhaps 27,000 years old have been found in Africa, Europe, and Asia. The most complete skeleton is 1.6 million years oldand was discovered near Lake Turkana, Kenya. Some paleoanthropologiststhought that this represented a more primitive species, and called it Homoergaster (“work person”), but others consider it Homo erectus. Homo ergaster was the first Homo species to resemble ours in size.




EARLY HOMO SPECIES

Homo ergaster usedstone tools tobutcher animalcarcasses andprobably both huntedprey and scavengedfrom carcasses.

WORK PERSONHomo ergaster is a controversial African hominidrecognized in 1975. Its large brain, relatively flatface, and small cheek teeth all suggest that Homoergaster was more closely related to Homo speciesthan to the australopithecines. Like other Homospecies, Homo ergaster was taller and larger thanmost australopithecines. It also took longer toreach adulthood and lived for longer than earlierhominids. In some details, however, Homo ergasterresembled australopithecines more than modernhumans. Its thorax tapers upward (ours is morecylindrical) and its shoulder girdles were closertogether than those of modern people.

TURKANA BOYOne of the most complete of allfossil hominids is the skeleton of theTurkana boy. The slim and tallproportions suggest that Homoergaster was adapted for movingquickly across the tropical grasslandsof the time. Anatomical featuressuggest an early human unlikely tobe capable of controlling itsbreathing precisely enough forcomplex speech in the way thatmodern humans can.

The Turkana boy had largerteeth and more powerful jawand neck muscles thanmodern humans.

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SOPHISTICATED TOOLSThe earliest Homo species

made crude chopping andcutting tools from stone cores

and flakes. Homo erectus refined toolconstruction by producing cleavers

and pear-shaped hand-axes of fairlystandardized shapes. Such tool kits

helped Homo erectus to butcher big gamelooted from carnivorans’ kills or perhapshunted with spears. This species probably livedin caves but might have built simple shelters ofbranches. Quite likely Homo erectus knew howto use fire for cooking and keeping warm.

BROW RIDGES AND BIG BRAINSHomo erectus approached modern humans inthe size of its brain. It had a brain capacity of around 67 cu in (1,100 cc) whereasmodern humans have a brain capacity ofabout 90 cu in (1,500 cc). Unlike the browridges of neanderthals, which were lightenedinternally by hollow sinuses, the ridges ofHomo erectus were mostly solid bone.

The thoraxof Homoergastertapersupward.

Fossilized jaws and teeth suggestthat Homo ergaster ate softer food than earlier hominids. It hadprobably developed cooking skills.

UPRIGHT PERSON

Scientific name: Homo erectusSize: 5 ft 9 in (1.8 m) tallDiet: Tubers, carrion, small animalsHabitat: Tropical grasslandsWhere found: Africa and AsiaTime: Late Neogene (Pleistocene)Related species: Homo ergaster, Homo antecessor

Stone handaxe

EARLY HOMO SPECIES

The skull bones ofHomo erectus werethicker than those ofmodern humans.

Prominentbrow ridges

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THE NEANDERTHALS (HOMO NEANDERTHALENSIS) are the mostfamous of fossil hominids and are often characterized as IceAge “cave people.” They used tools and fire, probably had a form of language, and may have lived in family groups.Unlike our own species, however, they did not create art, decorate their bodies with paint or jewelry, ordemonstrate clear planning to their activities. An olderneanderthal-like species, called Homo heidelbergensis,was an advanced hominid that might have beenancestral to the neanderthals and perhaps to our own species. It was long regarded as intermediatebetween Homo erectus and Homo sapiens and came to be known simply as “archaic Homo sapiens.” Today most paleontologists recognize it as a distinct species.




NEANDERTHALS

NEANDERTHALIn contrast to fossils of Homo sapiens, which have slim proportions suggestive of a tropical climate, neanderthalswere stocky with massive, thick-walled, heavily muscled bones. The stocky proportions of neanderthal skeletons show that this species was built for life in cold environments.Neanderthal people have often been depicted as dark and hairy. In reality, we have no idea as to how much body hair they may have possessed. They may have used clothing. Also, because they lived in cold environments, their skin may have been light-colored, as they did not need dark skin to protect from the sun. They lived from about 200,000 to 30,000 years ago.

The chin was lesswell developedthan that of Homo sapiens.

The lower legs and arms wereproportionally shorter than thoseof modern people. Animals fromcolder climates generally haveshorter extremities than thosefrom warmer places.

HEIDELBERG MAN AROUND THE WORLDSome researchers believe that various hominidfossils found at locations as far apart as Zambia,Ethiopia, France, and China should be includedin the species Homo heidelbergensis. Europeanspecimens come from Greece, Germany, France,Spain, and England. The famous Broken Hillskull from Zambia, originally named Homorhodesiensis, is thought by some to bean African Homo heidelbergensis.

Jaw of Homoheidelbergensisfound inHeidelberg, Germany

Ordovician 488.3–443.7

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NEANDERTHALS

NEANDERTHAL

Scientific name: Homo neanderthalensisSize: 5 ft 6 in (1.7 m) tallDiet: Probably fruits, berries, nuts, and largeand small animalsHabitat: Open woodlandWhere found: Europe, Asia, and AfricaTime: Late Neogene (Pleistocene)Related species: Homo heidelbergensis, Homosapiens, Homo antecessor

BROAD NOSES AND PROMINENT JAWSNeanderthals had very broad noses thatmay have helped warm cold air. Their frontteeth were large and often heavily worn,

suggesting that they were frequently used tohold objects. The cheekbones were also large

with an inflated look, while most of the skull andjaws were stretched forward relative to those ofmodern people. A bulging area on the very back

of the skull, called the occipital chignon, is adistinctive feature of neanderthal skulls.

BURYING THE DEADA number of neanderthal skeletons, mostly fromsouthwest France, are preserved in a curled upposture and appear to have been buried by othermembers of their species. Some experts havetherefore argued that neanderthals buried theirdead. This is hard to prove, as the specimens maysimply have died while sleeping and later beencovered naturally by sediment. One such skeletonhas abundant pollen associated with it, leading to suggestions that bunches of flowers had beenplaced on the body before burial. This isdebatable however.

Their hand bones showthat they could carefullymanipulate objects buthad a more powerful gripthan modern people.

This body islying on its backwith its armsover the chest.

Neanderthals had thick-archedbrow ridges over the eyes. Thefunction of these brow ridgesremains unclear.

Neanderthals had large brainsmeasuring 80 to 106 cu in (1,300 to 1,740 cc). Anaverage measurement forHomo sapiens is 90 cu in(1,500 cc).

Telltale scratch marksindicate that neanderthalsheld food between theirteeth while cutting off partof it with stone tools.

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MODERN HUMANS – HOMO SAPIENS – are perhaps the mostsuccessful species of large-bodied mammal ever, inhabitingvirtually every habitat on every continent and with moreindividuals (over six billion) than any other large animal.Fossils, genetics, and studies of living people show thatHomo sapiens is an African species that evolved from Homoheidelbergensis or a similar species around 200,000 years ago.Homo sapiens reached Europe at least 40,000 years ago.Evidence such as prehistoric art and ceremonial burialdistinguish the advanced culture of our species from otherhominids. Around 10,000 years ago Homo sapiens began to domesticate plants and animals and develop farming.Having continual supplies of food allowed humans evenmore time to develop culturally.




HOMO SAPIENS

CRO-MAGNON PEOPLENamed after a site in the Dordogne,France, Cro-Magnons were a Europeangroup of Homo sapiens with an Africanphysique. While they were muscular andwell built, they lacked the thick bonesand notably stocky proportions ofneanderthals. Art and symbolism wereimportant in their lives, and they leftabundant representations of animals on cave walls and as sculpture. They used natural materials as paints and made ornaments to decorate their bodies.

Though other Homospecies may alsohave used furs andskins as clothing,Homo sapienscreated complexgarments.

ADVANCED TOOLSHomo sapiens have developedmore types of tools for moredifferent uses than any other animal.The early tools made by our speciesfrom stone, bone, antler, or wood are often more complex, andmanufactured for more delicateuse, than those of other hominids.Important Cro-Magnon toolsinclude spear-throwers anddouble-pointed blades, barbedharpoons and the burin, a chisel-liketool used to shape other tools aswell as produce art and jewelry.

Cro-Magnonantler tool

NEANDERTHALDEBATE Most anthropologistsregard the neanderthalsas a separate species fromHomo sapiens. However,some think that the two mayhave hybridized (interbred)and that modern people there-fore incorporate neanderthalDNA. A 25,000-year-old skeletonfrom Abrigo do Lagar Velho, Portugal,appears to combine features of bothneanderthals and modern humans.Perhaps, rather than killing off the last neanderthals, the modern humanpopulation absorbed them by interbreeding.

Modern humansand neanderthalshave differentproportions.Possible hybridshave intermediateproportions.



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HOMO SAPIENS

MODERN HUMAN

Scientific name: Homo sapiensSize: 5 ft 9 in (1.8 m) tall (for Cro-Magnons)Diet: Seeds, tubers, nuts, fruit, shellfish,fishes, large and small animalsHabitat: Originally woodlands, grasslands,and coastlines; later nearly all land habitatsWhere found: Worldwide except most ofthe polar regions and some remote islands Time: Late Neogene (Pleistocene onwards)Related species: Homo neanderthalensis,Homo antecessor, Homo heidelbergensis

CAVE ARTHomo sapiens are unique amongthe hominids in producingart. Paintings and sculptureallowed early artists to expressabstract concepts and toimpress other tribe members.Perhaps the images also hadgreat spiritual significance.Many prehistoric paintingsdepict prehistoric animals with remarkable accuracy.

The limb bones of Cro-Magnonpeople are long and slim, likethose of their African ancestors.

Cave paintings at the Lascaux site in France show aurochs (a type of cattle that is now extinct),horses, and other animals.

SPREAD AROUND THE WORLDFrom its origins in Africa about

200,000 years ago, Homo sapiensspread around the world.

Asia was the first area theymoved into, from where the

species probably reachedAustralasia and the Pacific

Islands by building boats andusing land bridges when the

seas were low. The species alsospread into Europe and isthought to have reached the

Americas by 15,000 years ago.

Homo sapiens has a distinctive skullshape, with a taller forehead andlarger and more rounded craniumthan other Homo species.

Europe

Africa

Australasia

Pacific Islands

PA C I F I C O C E A N

SouthAmerica

NorthAmerica

Asia

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RABBITS AND RODENTS probably both appeared in the Paleocene(65.5–55.8 million years ago). These superficially similar mammalshave gnawing teeth and are mainly plant-eaters. Both might bedescended from ancestors such as Zalambdalestes from the LateCretaceous. Rabbits, which are types of lagomorph, have remainedfairly similar throughout their history. Rabbitlike pikas (anotherlagomorph group) were more widespread than rabbits duringMiocene times (23–5.3 million years ago), but have since declined.Rodents are the largest group of mammals – there are more species(more than 1,700) and more individuals than of any other group.Gliding, burrowing, and climbing rodents have fossil records datingfrom the Eocene (55.8–33.9 million years ago).

EPIGAULUSMylagaulids were a peculiar NorthAmerican group of powerfully builtburrowing rodents. Epigaulus is oneof the best-known mylagaulidsand had spade-like paws andhorns above the snout.Though advanced mylagaulids such asEpigaulus were horned, thiswas not true of the most primitive forms. An oldidea is that horned and hornless mylagaulidswere males and females of the same species.However, further studies have shown that bothsexes had horns, and that there were differentspecies with and without horns. Mylagaulidswere members of the squirrel-beaver group.

The eyes weresmall, suggestingthat Epigaulus didnot rely on eyesightthat much.

The large gnawing incisorscould also have been used indigging. Living mole rats andother burrowing rodents usetheir teeth in this way.

The horns mighthave been usedin fights, ormaybe theyhelped withdigging.




SOUTH AMERICAN RODENTSSouth America is home to a distinct group ofrodents called caviomorphs. These appear to havearrived from Africa during the Eocene. The giantcaviomorphs Neochoerus and Protohydrocoerus were as large as modern tapirs – they could have weighed450 lb (200 kg). Biggest of all was Phoberomys. Thiswas the size of a bison and weighed up to a ton.

PREHISTORIC RABBITS AND RODENTS

Neochoerus skull

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Broad, spadelikepaws and longstraight claws wereused for digging.

BURROWERS AND BUILDERSBeavers are large rodents that belong to the same group as squirrels. Somefossil beavers were much like the livingbeaver. Paleocastor was a small burrowingbeaver that lived on the plains of NorthAmerica in the Oligocene and Miocene(33.9–5.3 million years ago). It probablylooked like a living prairie dog and isfamous for having made vertical spiral-shaped burrows up to 5 ft (2.5 m) deep. These were long known as “Devil’s corkscrews.” Tooth and clawmarks made by Paleocastor are preservedon the side walls of the burrows, andsome Paleocastor skeletons have beenfound preserved within their burrows.

PREHISTORIC RABBITS AND RODENTS

RABBITS, HARES, AND PIKASThe earliest lagomorphs datefrom the Eocene and includerabbits, hares, and pikas. Thepikas, which look like small short-eared rabbits, were abundant in theMiocene but have since declined. Todaythey live in mountains in North Americaand Asia. Fossil rabbits such as Hypolaguslook similar to living types.

Section ofspiral-shapedburrow

Paleocastor skeleton in burrow

Hypolagus skull

EPIGAULUS

Scientific name: EpigaulusSize: 30 cm (12 in)Diet: Roots, seeds, grassesHabitat: PlainsWhere found: North AmericaTime: Late Neogene (Miocene–Pliocene)Related genera: Ceratogaulus, Mylagaulus



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DURING THE PLEISTOCENE, from 1.8 million years ago and until as recently as8,000 years ago, unusual mammals inhabited the Mediterranean islands.These had been cut off from their ancestors and each other by rising sealevels. The Balearic Islands were home to Myotragus, a goatlike creature with unique rodentlike gnawing teeth. Candiacervus, a small deer with club-shaped antlers, was an inhabitant of Crete. Prolagus, the last European pika(a rabbitlike mammal) lived on Corsica and Sardinia. Hippopotamuses,elephants, and deer on these islands were remarkable for being dwarfs,generally less than half the size of their ancestors. The elephants, forexample, grew to little more than half the height of a human. By contrast,other Mediterranean mammals, including lizards, owls, and dormice, becamegiants. These creatures probably became extinct through a mixture of beinghunted by humans, competing with farmed animals, and changes in climate.

Dwarf elephants lived offplant food that grew closeto the ground. They mighthave pushed over smalltrees and shrubs to reachleaves and fruit.

ISLAND GIANTS AND DWARFS

GIANT DORMICELeithia, a giant dormouse from Malta and Sicily, wasclosely related to living forest dormice. However, it was a giant in comparison with living dormice, reachingabout 16 in (40 cm) in total length – about as large as a squirrel. Living dormice are agile climbers, andLeithia probably was too. However, whereas livingdormice are also mostly nocturnal, Leithia might havebeen more active during the daytime. This is becausethere were few predators on the islands, so it would not have needed to hide under the cover of darkness.

Like its living relatives,Leithia probably had dark markings around the eyes and a bushy tail.



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ISLAND GIANTS AND DWARFS

DWARF ELEPHANTSElephas falconeri was a miniature island-dwelling elephant with a shoulder height of 3 ft (90 cm). On the Mediterranean islandsthe territories were smaller than on the main-land, and reduced quantities of food meantthat smaller individuals were more likely tosurvive than large ones. As a consequence, the body size of Mediterranean elephantsbecame progressively smaller as time went by.

DWARF ELEPHANT

Scientific name: Elephas falconeriSize: 5 ft (1.5 m) long, 3 ft (90 cm) tall Diet: Leaves, grasses, fruitHabitat: ForestsWhere found: Malta and SicilyTime: Late Neogene (Pleistocene)Related species: Elephas melitensis, Elephas mnaidrensis

Like other elephants, dwarf formshad tusks that they probably usedin fights and as tools. They wouldhave used the trunk to bring waterand food to the mouth.


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DINOCERATANS, THE “TERRIBLE HORNED” MAMMALS, were plant-eating,rhinoceroslike hoofed creatures famous for their paired horns andtusklike canine teeth. The earliest dinoceratan, Prodinoceras, firstappeared in Asia during the Paleocene (65.5–55.8 millionyears ago), but nearly all later types are from NorthAmerica. How dinoceratans are related to othermammals is in dispute. They are probably part of thehoofed mammal (ungulate) group and havesimilarities with some of the South Americanhoofed mammals. Another idea is thatdinoceratans are closely related to pantodontsand tillodonts. A more controversial view is that dinoceratans descendfrom the anagalids, a smallgroup of rabbitlike mammals.

Uintatheriumhad a barrel-shaped body.



Cast of the skull of Uintatherium

UINTAH BEASTThe largest and best-known dinoceratan,Uintatherium, was as big as a living white rhino,and lived about 40 million years ago. It wasnamed in 1872 after the Uintah Indians, atribe that, like Uintatherium, lived in Utah.When first described, there was controversyover whether Uintatherium was an elephant or not. Today it is clear that elephants anddinoceratans are not at all closely related.

HORNS, BUMPS, AND TUSKSThe various shapes on the long skulls of dinoceratanssuch as Uintatherium and Eobasileus were probablydisplay structures used to signal sexual maturity.Males appear to have had bigger horns and a morepronounced flange (projection) on the lower jaw. It is likely that they fought using these structures,perhaps pushing against one another with the hornsand crests and biting one another with the tusks. The advanced dinoceratans

had columnlike legs.

TERRIBLE HORNS

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BIG SKULL BUT SMALL BRAINCompared to later hoofed mammals,dinoceratans had small brains. Whilethe skull of Uintatherium or Eobasileusmight be nearly 3 ft (1 m) long, thespace in the skull for the brain was onlyabout 4 in (10 cm) long. Megacerops, abrontothere, was another Eocene giantwith a small brain. Smaller brainsappear true of most mammals of thetime. Equus, the modern horse, clearlyshows the much bigger brain typical of later mammals.

TERRIBLE HORNS

UINTAH BEAST

Scientific name: UintatheriumSize: 11 ft (3.5 m) longDiet: Leaves, fruit, waterplantsHabitat: ForestsWhere found: North AmericaTime: Early Paleogene (Eocene) Related genera: Eobasileus, Tetheopsis

Equus skull

Megacerops skull

Uintatherium skull

In horned dinoceratans, the pairof horns at the back of the skullare always the biggest. Thehorns were blunt and may have been covered in skin rather than a horny sheath.

The enlarged flanges on the lowerjaw may have helped protect thetusklike canines. Both the tusks and jaw flanges were betterdeveloped in males.

Like elephants, advanceddinoceratans had veryshort finger, toe, hand,and foot bones andwalked only on theirtoes. Such hands andfeet are suited for weightbearing, not for running.



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PRIMITIVE HOOFED MAMMALSFOR MANY YEARS, experts grouped a large number of primitive hoofedmammals together as the Condylarthra. This was always controversial,as not all creatures placed in that group shared the same ancestor.Condylarths were subsequently redefined, and now consist of a specificgroup of related hoofed mammals from the Paleogene. Mostcondylarths were four-footed plant eaters, ranging from the size of a ratto the size of a sheep. Some condylarths had claws, though others haddeveloped blunt hooves. Their teeth show that they were mainly planteaters, and some had enlarged, squarish molars and enlargedpremolars suited to pulping plant material. Most lived in woods orforests, where they browsed on the undergrowth.

Phenacodus


Phenacodus’s long limbswere quite flexible, so itwas not as specialized forrunning as later ungulates,such as horses. Thesehave stiffened limbs.

Phenacodus mayhave been dappledor striped forcamouflage in the undergrowth.

Didolodus

PHENACODUSThe most famous condylarth is Phenacodus, mostly because experts used to think it was an ancient ancestor of the horse. Like horses,Phenacodus had a skeleton suited to a lifestyle of running in the openwoodland where it lived. It wasabout the size of a sheep, andhad proportionally longerlimbs than many othercondylarths. The toeson the outside of itsfeet were small,meaning that most of its weightwas carried on itsthree middle toes.This suggests thatPhenacodus was a good runner.

MYSTERIOUS SOUTH AMERICANSDidolodontids were South American hoofed mammalsthat were probably closely related to phenacodontids.However, their anatomy is also similar to that of thelitopterns – the horse and camellike South Americanungulates. Some experts therefore regard didolodontidsas primitive members of the South American ungulategroup, and as possible ancestors of the litopterns.



RATLIKE HOOFED MAMMALSSome condylarths were tiny.

Hyopsodus, the best-known of the hyopsodontid group,

was a rat-sized animalabout 1 ft (30 cm) long. It had short legs,

a flexible body, andfairly long, clawed

digits. It probablyforaged in the

undergrowth,though it may also

have been ableto climb trees.

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PRIMITIVE HOOFED MAMMALS

PHENACODUS

Scientific name: PhenacodusSize: 5 ft (1.5 m) longDiet: LeavesHabitat: Grasslands, open woodlandWhere found: North America, EuropeTime: Paleogene (Paleocene–Eocene)Related genera: Tetraclaenodon, Copecion

AARDVARK PROTOTYPE?Ectoconus was a sheep-sized

condylarth from NorthAmerica and perhaps Asia.

Its body shape has beencompared with that of

the aardvark, and for thisreason some experts have arguedthat aardvarks are living membersof the condylarth group. Unlikeaardvarks, Ectoconus would havebeen no good at digging, as it lacked large, curved claws.

Phenacodus hadfive toes on its feet.Each toe ended ina small, blunt hoof.

Like most condylarths,Phenacodus had along, flexible tail.

BIG LLAMAThe litopterns were a group of panameriungulatesthat resembled camels and horses. One of the biggestand best known of the litopterns was Macrauchenia(“big llama”). It was about the same size as a largemodern camel and had stocky limbs and three-toedfeet. Macrauchenia is most famous for its nostrils,which were located high up on the top of its head.Some experts think this shows that it had a shorttrunk,

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SOUTH AMERICAN HOOFED MAMMALSUNTIL ABOUT 10,000 YEARS AGO, South America was hometo a range of unusual hoofed creatures – known as themeridiungulates and panameriungulates. Some of theseanimals resembled hoofed mammals from elsewhere,such as horses and camels. These similarities probablycame about because animals with similar lifestyles mayevolve in a similar way, even if they live in differentplaces. Exactly how meridiungulates relate to otherhoofed mammals is still unclear. Links with condylarths,dinoceratans, and other groups have all been suggested.But despite their diversity, there is evidence that allmeridiungulates share a single ancestor.

SKELETON OF MACRAUCHENIAMacrauchenia was discovered by Charles Darwin andnamed and described by Sir Richard Owen, two of themost important scientists of Victorian times. Darwin infact wrote of his impression that the skeleton appeared to be from a large llama. From the outside Macraucheniaresembled a camel, but, inside, its skeleton was verydifferent from a camel’s. The neck bones were moresimple and it had more teeth than a camel, for example.




Macrauchenia’s longneck resembled thatof a camel. It mayhave grazed from theground or browsedfrom trees.

BIG LLAMA

Scientific name: MacraucheniaSize: 10 ft (3 m) longDiet: Leaves and grassesHabitat: GrasslandsWhere found: South AmericaTime: Late Neogene (Pleistocene)Related genera: Windhausenia,Promacrauchenia

Macrauchenia’sjaws were linedwith 44 largechewing teeth.

It could probablykick powerfully with its hind limbs.

Its vertebrae suggestthat Macrauchenia hada small shoulder hump.

The bony nostrilopenings werelocated betweenthe eyes.

Short trunk,like that of amodern tapir

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FEET FOR FAST RUNNINGSome litopterns were fast running animals suitedfor life on the open grasslands. Such grasslandenvironments appeared in South America 15million years earlier than they did elsewhere.Most litopterns, such as Macrauchenia andTheosodon, ran on three toes. But some, such as Diadiaphorus and Thoatherium, evolved slimlimbs and one-toed feet. Thoatherium even lost its two side toes.

Macrauchenia

SOUTH AMERICAN HOOFED MAMMALS

Incisors

Deep, roundedbody, like that of a large horse

Macrauchenia’sthigh bone waslonger than itslower leg bones.This suggeststhat it could notrun very fast.

Macrauchenia hadthree-toed feet, likethose of rhinos.

All litopterns hadsimple ankle joints. In fact, their namemeans “simple ankle.”

TOXODONTSThese plant eaters rangedfrom the size of a pig to thesize of a rhinoceros. Theybelonged to a group ofmeridiungulates called thenotoungulates. The best-known toxodont is Toxodon, a huge, hippopotamus-likeanimal with large chewingteeth and prominent incisors.

Foot ofTheosodon

Foot ofDiadiaphorus

Foot ofThoatherium

Chewing teeth

Skeleton of Toxodon

Short legs withthree toes

Barrel-shaped body



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AT HOME ON THE GRASSLANDSMacrauchenia lived on grasslands and open woodlands in SouthAmerica. These habitats must have looked very similar to thepampas grasslands that cover southern South America today.Macrauchenia’s teeth suggest that it ate tough vegetation, so itmay have fed on grasses as well as from trees. If Macrauchenia didhave a trunk, it could have used it to grab leaves and branchesthat would otherwise have been out of its reach. Its long neckand large size would have helped Macrauchenia to keep a lookoutfor predators, such as wolves, lions, and giant running bears.



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SOUTH AMERICAN HOOFED MAMMALS

ARSINOITHERESThese rhinoceros-like uranotheres lived in Asia,Europe, and Africa 40–30 million years ago, inthe Eocene and Oligocene epochs. The best-known arsinoithere is Arsinoitherium – a large, heavy animal with two massive horns onits skull. The largest individuals of Arsinoitherium(probably old males) were about the size ofsmall elephants. Unlike rhinoceros horns,arsinoithere horns were hollow. They havegrooves on their surface, showing that therewere blood vessels on the outside, and that the horns were probably covered in skin.

ONE OF THE MOST PECULIAR groups of mammals is the Uranotheria, a collection of plant-eating, hoofed mammals that includes elephants,seacows, and hyraxes. It might seem strange that these very differentcreatures are thought to be related, but they share features not seen in other mammals. The earliest members of these groups seem to have been similar in appearance. The first elephants, for example,were not giant creatures with trunks, but dog-sized animals probablysimilar to modern-day hyraxes. In fact, hyraxes may show how theearliest uranotheres lived – as small, grazing plant eaters. A latergroup of uranotheres, called the tethytheres, evolved an amphibiouslifestyle. Some of these became committed to life in water andeventually evolved into the first seacows.

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URANOTHERES

Arsinoitherium’s teethhad tall crowns and couldhave been used to chewvery tough plant material.

ARSINOITHERIUM

Scientific name: ArsinoitheriumSize: 12 ft (3.5 m) longDiet: Tough leaves and stemsHabitat: Woodland, wooded grasslandWhere found: Egypt and OmanTime: Late Paleogene (Eocene)Related genera: Crivadiatherium, Paleoamasia




Males had largerand more pointedhorns than females.

Arsinoitherium

Arsinoitherium had acomparatively smalland simple brain.

Two smallerhorns grewfrom the backof the skull.

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URANOTHERES

Arsinoitherium’s limbswere stout and heavy.

Tusklikefront teeth

Skeleton of Paleoparadoxia

It had tusklike frontteeth and cylindricalchewing teeth.

The front legsmay have beenused as paddleswhen swimming.

Each foot had five blunttoes, each tipped witha small hoof.

Its shoulders were massive and powerfullymuscled.

Broad, heavybody

DESMOSTYLIANSDesmostylians, such as Paleoparadoxia, were sea-dwelling uranotheres. They lived on theedges of the Pacific Ocean during Oligoceneand Miocene times (33.9–5.3 million years ago) and probably fed on seaweeds.Desmostylians perhaps looked like a crossbetween a hippopotamus and a walrus. Although they lived mainly in the sea, they could probably walk clumsily on land.

Kvabebihyrax

Short, stockylimbs

Arsinoitheres probablydigested their food in an enormous hindgut region.

HYRAXES Modern hyraxes are small African mammals thatlook like guinea pigs. Fossil hyraxes, however, were quite different and came in a huge range of shapes and sizes. Kvabebihyrax, shown here, was the shape of a hippopotamus and may havebeen amphibious. Titanohyrax was the size of asmall rhinoceros. Antilohyrax was a long-leggedrunner resembling an antelope. Other fossilhyraxes had long heads and would have lookedsimilar to modern-day pigs.



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THREE-TOED FEETLike modern horses, Hipparionwas a grassland animal. Earlierhorses were probably inhabitantsof forests. Unlike modern horses,which only have one toe on eachfoot, Hipparion had three-toedfeet. However, most of its weightwas borne on the enlargedcentral toe. Hipparion and itsrelatives were distant cousins of horses such as Merychippus,which were the probableancestors of modern horses.

TEETH FOR GRASS-EATINGAdvanced horses, such asHipparion, had large, high-crowned molar teeth withcomplicated chewing surfacesmade up of loops of enamel.Their premolars became large and squarish and came to look like the molars. Thesepowerful, resistant teeth allowedadvanced horses to eat roughgrasses, although they mayinitially have evolved in response to the accidentalchewing of sand and grit.

In Hipparion a largebony pocket called thepreorbital fossa grewon the side of thesnout. This was largerin males than females,though its functionremains unknown.

Life in open, grasslandenvironments favored theevolution of large body sizeand long limbs in horses.

PERISSODACTYLS ARE A GROUP ofhoofed, odd-toed, plant-eatingmammals, and include horses,tapirs, rhinoceroses, andbrontotheres. Horses, the mostsuited to open grasslands,appeared in the Eocene(55.8–33.9 million years ago)and about eight species of themsurvive today. Successive groupsof horse species evolveddifferent features and bodysizes to suit their environments.Hipparion, shown here, was oneof several species of three-toedhorse that lived on theNorthern Hemispheregrasslands during the Miocene (23–5.3 million years ago).

HORSES



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HORSES

HIPPARION

Scientific name: HipparionSize: 5 ft (1.5 m) longDiet: Leaves and grassesHabitat: Grasslands, open woodlandsWhere found: North America, Europe, Asia,and AfricaTime: Neogene (Miocene–Pleistocene) Related genera: Cormohipparion, Nannippus,Neohipparion

Modern horses have speciallocking mechanisms, calledstay apparatus, on their limb bones that allow themto remain standing with a minimum of effort.Hipparion did not have stay apparatus.


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BRONTOTHERES AND CHALICOTHERESTHESE TWO GROUPS OF CREATURES were odd-toed hoofed mammals, or perissodactyls. Brontotheres were large, rhino-like animals knownonly from North America and Asia in the Eocene (53–33.7 millionyears ago). Early brontotheres were about the size of sheep, but later ones were giants, up to 8 ft (2.5 m) tall at the shoulder. Somesported horns on the end of their snouts that grew in V or Y shapes.Chalicotheres were horselike perissodactyls with long forelimbs andcurved claws on their fingers and toes. First appearing in the Eocenein Asia and Europe, they later spread to Africa and North Americaand survived into the early Quaternary.

BRONTOTHERE HORNSAs brontotheres evolved, their horns became larger. In later brontotheres, males had larger horns thanfemales. This suggests that brontothere males usedtheir horns for displaying and fighting, like the twomale Brontops shown here. Early brontotheres had

tusk-like front teeth, butBrontops and other later

brontotheres lackedthese and instead

had a mobileupper lip.




Powerful muscles wereattached to the massivespines on the shouldervertebrae and formed a prominent hump.

In some brontotheresone of the wrist bones,a bone called thetrapezium, was absent.No one knows why.

The surface textureof the horns showsthat they werecovered in skin.

Weak teeth suggestthat brontotheresmostly ate soft leaves.

Injuries found on skulls andribs suggest that brontotheresfought each other with theirhorns, perhaps for dominance,territory, or mating rights.

SKULL OF BRONTOPSLater brontotheres, such asBrontops, had very shortenendfaces and eyes positioned closeto the nose. Brontops had twoshort horns that stuck upwardand outward.

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BRONTOTHERES AND CHALICOTHERES

Brontops

A CLAWED “HOOFED MAMMAL”Moropus was a chalicothere from North America. Like allchalicotheres, it had massive, powerful front legs and curvingclaws on its hands. Chalicotheres may have been digging animalsthat fed on roots and tubers. However, their wrists were not verymobile, and their teeth lack the wear marks normally created bysoil and grit. It is more likely that chalicotheres were browsers that pulled branches down from trees.

BRONTOPS

Scientific name: BrontopsSize: 17 ft (5 m) longDiet: LeavesHabitat: Open woodlandWhere found: Western North AmericaTime: Paleogene (Eocene) Related genera: Menops, Megacerops,Duchesneodus

Giant brontothereshad stout, shortlimbs suited tocarrying theimmense weightof their bodies.

LAST OF THEBRONTOTHERESEmbolotherium and its relatives were anadvanced group ofbrontotheres, foundonly in Asia. They wererelated to Brontops.Embolotherium was one ofthe last and largest of thebrontotheres. It wassimilar in size to Brontops,but was equipped with alarge, forked nose horn.

The hip bones werevery broad, probablyto help support theweight of the body.

Its long, flexibleneck allowedMoropus toreach up intobranches.

Its skeletonsuggests that

Moropus couldstand up on its

back legs.

The powerfulfront legs werelonger than theback legs.

Moropus couldhold its claws upoff the groundwhen it walked.

Brontothere tailsprobably endedin a tuft of hairs.

Its broad mouthcontained small,rounded incisor teeth.

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RHINOCEROSESTODAY THERE ARE FIVE SURVIVING SPECIES ofrhinoceros. They are plant-eaters with hornsmade from keratin – the same structure thatskin, nails, and claws are made from. Fossilrhinoceroses were diverse and evolved manydifferent lifestyles and body shapes. Perhapsthe most primitive rhinoceroses were thehyracodontids, or running rhinoceroses.These were hornless, long-legged creatureswith simple teeth suited for browsing.Another family, the amynodontids, includedamphibious rhinoceroses with short mobiletrunks, like the trunks of modern-day tapirs.Amynodontids appear to have been veryprimitive rhinoceroses, and it has even beensuggested that they are not rhinoceroses at all, but part of the tapir group ofperissodactyls instead.

THE BIGGEST LAND MAMMALParaceratherium was a gigantic hyracodontid rhinoceros. Incontrast to the small early hyracodontids, Paraceratheriumwas 18 ft (6 m) tall at the shoulder and weighed around15.7 tons (16 tonnes), making it the biggest landmammal of all time. Its skull alone was about 4 ft (1.3 m) long. Paraceratherium wasprobably a browser that ate leaves from the tops of trees.

ELASMOTHERIUMThe surviving species of rhinoceros are members of the rhinocerotid group. The biggest rhinocerotid wasElasmotherium, which reached 16 ft (5 m) in length andhad an immense conical horn 6 ft 6 in (2 m) tall on itsforehead. Elasmotherium lived in the Pleistocene(1.81–0.01 million years ago).




Despite its great size,Paraceratherium hadlong, slim legs andcould probably run.

Scientific name: ParaceratheriumSize: 9 m (30 ft) longDiet: Leaves and twigsHabitat: Open woodlandWhere found: Eastern Europe, AsiaTime: Palaeogene–Neogene(Oligocene–Miocene)Related genus: Forstercooperia

PARACERATHERIUM

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Triassic 251–199.6 299–251 Jurassic 199.6–145.5 Cretaceous 145.5–65.5 Neogene 23–present


WOOLLY RHINOCEROSCoelodonta, the woolly rhinoceros of Asia andEurope, lived in the Pleistocene (1.75–0.01million years ago). It is known from bodiespreserved in frozen soil and from prehistoriccave paintings. We therefore have a good idea of what Coelodonta would have looked like. It had two large horns, a hump over its shoulders,thick stocky limbs, and long, dark fur.

LIVING LIKE A HIPPOPOTAMUSTeleoceras was a long-bodied rhinoceros from North America that lived in the Miocene (23.5–5.3 million years ago). It had very short legs and a small nose horn. Teleoceras had long teeth,which show that it was a grass-eater. It probably lived like ahippopotamus, wallowing in water but grazing on land at night.Its fossils are frequently found in the beds of ancient streams.

RHINOCEROSES

Paraceratherium

Its long neck enabledParaceratherium tobrowse from trees.

Hollows in the sidesof Paraceratherium’sback bones madethem light but strong.

Its skull structuresuggests thatParaceratherium hada flexible upper lip.

Some Teleocerasspecies had aflexible upper lip.

Barrel-shapedbody

Tall cheek teethfor chewingtough grass Teleoceras probably

walked along thebottom of rivers.

Three stout toessupported itsweight.

Paleogene 65.5–23

MOERITHERIUMOne of the most primitive known proboscideans is Moeritherium.It lived in Africa in the Eocene. Moeritherium’s skull indicates that it had an enlarged upper lip, but experts do not knowwhether this was a true trunk. Its bulky body was similar in shape to a hippopotamus, and its legs were short. These featuressuggest that Moeritherium wallowed in lakes and rivers, perhapsfeeding on water plants. Enlargedincisor teeth in both theupper and lower jawsformed small tusksthat probablyprotrudedfrom itsmouth.

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PROBOSCIDEANSTHE TWO MODERN-DAY species of elephant are the living representatives of amuch larger group of hoofed mammals, called the proboscideans. The earliest known proboscidean was Phosphatherium from the Paleocene(65–56 million years ago). It weighed only about33 lbs (15 kg) and was just 2 ft (60 cm) tall atthe shoulder. Later proboscideansincreased in size and evolved straight,columnlike legs. They also grewmassive tusks in their upper jaws,which they used for fighting andgathering food. The structure of theirskulls shows that nearly all fossilproboscideans had a trunk.

Phiomiaprobably had a short trunk.




Primitive proboscideans likeMoeritherium had not yetdeveloped the columnlike legs of an elephant.

PHIOMIAThis primitive proboscideanlived in northern Africaduring the Oligocene (33.9–23 million years ago).Phiomia was larger thanMoeritherium but still onlyabout as big as a large modern horse. It hadcolumnlike legs, a shorterneck, and a much bigger skullthan more primitive elephants.Like later elephants, Phiomiahad air-filled spaces, calleddiploe, in its skull. This meantthat its skull was light, despiteits size.

SHOVEL-TUSKERSLike nearly all primitive proboscideans, Phiomiahad tusks in both its upper and lower jaws. Itslower jaw was long and had flattened, square-tipped tusks. This formed a shovel-shaped jawthat could have been used to scoop up waterplants, or cut branches or bark from trees.Later, more advanced kinds of proboscidean,such as Gomphotherium, hadsimilar lower jaws.

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ELEPHANTS

Gomphotherium was about as big as an Asian elephant.

DEINOTHERESThese strange proboscideans had no

tusks in their skulls and two down-curved tusks in their lower jaws.These may have been used to digup roots, strip bark, or wrenchbranches down from trees.Deinotheres seem to have had shorter trunks than

living elephants.

GOMPHOTHERIUMA successful group of elephants calledgomphotheres spread around the worldin the Miocene and Pliocene (23–1.8million years ago). Gomphotheres, such as Gomphotherium, inhabitedmarshes, grasslands, andforests. Gomphotherium’s upperjaw tusks were probably usedfor fighting and display and,as in living elephants, werelarger in males than infemales. Elephants similar to Gomphotherium were theancestors of mammoths andof modern-day elephants.

The enlarged upperlip and nose mayhave formed a very short trunk.

Moeritherium’s neck waslonger than that of moreadvanced proboscideans.

MOERITHERIUM

Scientific name: MoeritheriumSize: 10 ft (3 m) longDiet: Water plantsHabitat: Lakes, rivers, riverside forestWhere found: Northern AfricaTime: Paleogene (Eocene–Oligocene)Related genus: Phosphatherium

Deinotherium was13 ft (4 m) tall atthe shoulder.

Skull ofPhiomia



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A FLEXIBLE TRUNKOld reconstructions of Platybelodon show it with ashort, wide trunk that would not have been veryflexible. This is because the reconstructions werebased on evidence from the more primitive Phiomia.The nasal openings in Phiomia’s skull show that itstrunk was short and poorly developed. However,Platybelodon had the same kind of nasal openings asmodern elephants. Like modern elephants therefore,Platybelodon probably had a long, flexible trunk.

PLATYBELODONPLATYBELODON WAS A WIDESPREAD “shovel-tusker”gomphothere. It had a long, scooplike tip to its lower jaw,formed by the tusk and mandible. In some specimens thelower jaw curved downward along its length, while in othersit was straighter and curved upward at the tip. Platybelodonwas once thought to have lived in marshes, where it used itslower jaw to scoop up water plants. Wear patterns on its tuskssuggest instead that Platybelodon mostly lived in grasslandsand forests and cropped tough vegetation from trees.



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PLATYBELODON

LOWER JAWThe wear marks onPlatybelodon’s lower jaw tusksshow that vegetation was oftenpulled across the tips of thetusks. Platybelodon probably used the tusks as blades. Itwould have grabbed a branchwith its long trunk and pulled itrepeatedly across the tusks untilthey sliced through the wood. Itseems that most of this branch-cutting happened where thetwo tusks touched one another,as this is usually the mostheavily worn area.

LEGS AND FEETLike all advanced elephants, Platybelodon had straight legs.Its knees were positioned directly above its ankles, soeach leg formed a column beneath its body. Platybelodon’sankles were very close to the ground because the bonesthat formed its feet were very short. Fatty pads under itsfeet supported the foot bones and helped to spread theanimal’s great weight as it walked.

PLATYBELODON

Scientific name: PlatybelodonSize: 3 m (10 ft) tall at shoulderDiet: Leaves, grasses, barkHabitat: Grasslands, forestsWhere found: North America, Africa, Asia, EuropeTime: Neogene (Miocene–Pliocene)Related genera: Amebelodon, Torynobelodon

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MAMMOTHS

DIMA THE MAMMOTHDima was the name given to a frozen male baby woollymammoth, recovered in1977 on the bank of theBerelekh River, Russia,and preserved in aremarkably completecondition. How Dimadied has been the subjectof debate. It has beensuggested that he drowned, fell intoa crack in the frozen ground, orbecame caught in wet mud. X-raysshow that Dima had not yet grownthe domed skull and tall shoulderhump seen in adult mammoths.

Shoulder hump




Mammoth hair, found onthe frozen specimens, canbe up to 3 ft (90 cm) long.

THE EIGHT SPECIES OF MAMMOTH were all true elephants, closely relatedto the two living species. Mammoth genetic material, or DNA, wasdiscovered in 1994 and found to be almost identical to that of livingelephants. The woolly mammoth (Mammuthus primigenius) is perhapsthe most famous fossil animal from the Pleistocene (1.75–0.01 millionyears ago). An inhabitant of the cold Ice Age grasslands, it had a shaggycoat, huge, curving tusks, and a tall, domed skull, but was small comparedto some other extinct elephants. As in living elephants, male mammothsprobably wandered on their own and fought for dominance withtheir tusks. Some males even died locked in combat and have beenpreserved this way as fossils. The last mammoths, a population of dwarf woolly mammoths, lived on Wrangel Island north ofSiberia and died out only 4,000 years ago.

WOOLLY MAMMOTHThese mammoths lived inherds and fed on grassesand other small plants,which they plucked withthe two “fingers” on thetips of their trunks.Several woolly mammothshave been found preservedin the frozen ground ofSiberia. Their fur, skin,muscles, and even theirstomach contents are still intact.These frozen specimens show that,unlike living elephants, mammothshad very short tails. This is probably becausea long tail would be vulnerable to frostbite.

Both male and female woollymammoths had long, curvingtusks. They used their tusksin combat and display, andas tools for gathering food.

Mammuthus primigenius

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MAMMOTHS

WOOLLY MAMMOTH

Scientific name: Mammuthus primigeniusSize: 11 ft (3.3 m) tall Diet: Grasses and other plant materialHabitat: Woodlands and grasslandsWhere found: North America, Europe, AsiaTime: Late Neogene (Pleistocene–Holocene)Related genus: Elephas (includes living elephants)

IMPERIAL MAMMOTHMammuthus imperator (Imperial mammoth) wasa giant North American Pleistocene mammothand one of the biggest elephants that ever lived. It was 12 ft (3.7 m) tall at the shoulderand its huge, curving tusks could be 14 ft (4.3 m) long. Many fossils have been found in California, where this mammoth inhabitedwarm grassland and woodland environments.Warm-weather mammoths probably lacked the furry coats of their cold-climate cousins.

The tuskswere so longand curvedthat theycrossed over.

CAVE PAINTINGSAbout 400 prehistoric cavepaintings and sculptures ofwoolly mammoths are known.Most have been found in Frenchor Spanish caves and are about30,000 years old. The paintingsshow mammoths with the samefeatures as the mammothspreserved in frozen ground,such as a shoulder hump andsmall, rounded ears. Somepaintings depict mammothsmoving in groups while othersshow mammoths fighting.

Hugecolumnlikelimbssupported its weight.

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THE LARGEST AND MOST SUCCESSFUL group of hoofedmammals are the artiodactyls, or even-toed hoofedmammals. All artiodactyls have distinctive ankle and foot bones that allow many of them to run fast.Their feet are symmetrical, and most forms have twoor four toes, hence the group’s name. Artiodactylsinclude three major groups that all first appeared inthe Eocene. The first group is the suiforms, includingpigs, hippopotamuses (hippos for short), peccaries,and various extinct relations. Unspecialized teeth and flexible snouts have allowed them to becomeomnivores that can eat most kinds of plant materialand fungi, as well as carrion and small animals. Manysuiforms had, or have, large fang- or tusk-like teethused for fighting and display. These tusks havebecome massively enlarged in the hippos. Thesecond artiodactyl group, the tylopods, includes the camels. The third group, the pecorans, includes giraffes, deer, and cattle.

HIPPOPOTAMUSESThe first hippos appeared in the Late Miocene. Two kindssurvive today – the large, amphibious Hippopotamus and the small, land-living Hexaprotodon. The recently extinctHippopotamus lemerlei was a pygmy river-dwelling hippo fromMadagascar. Hippos have huge, curving tusks at the front ofthe mouth. These are larger in males than females and are

used in fighting and displaying. Geneticstudies suggest that hippos may

be related to whales, but this is controversial.


DAEODON

Eyes located ontop of the head



Amphibious hipposhave elongated snoutsand lower jaws. Unlike many other suiforms,

entelodonts had only twotoes on each foot.

Incisors protrudeforward, and can be used for digging.

Entelodonts had smallbrains, but parts of thebrain devoted to smellwere well developed.

Bony cheek flangeswere especially large,with swollen ends.

PIGS, HIPPOS, AND PECCARIES

Skull of Hippopotamus lemerlei

Skeleton ofArchaeotherium

ANCIENT BEASTEntelodonts werepig- to bison-sizedsuiforms knownfrom Eocene andMiocene Europe,Asia, and NorthAmerica. They had long legs and deepbodies. Their huge skulls have bonybumps on the cheeks and lower jaws,crushing teeth, and huge, curving canineteeth. Archaeotherium was a successful pig-sized entelodont that lived across NorthAmerica and Asia.

Scientific name: DaeodonSize: 10 ft (3 m) longDiet: Vegetation, carrion, smaller animalsHabitat: Grasslands, open woodlandWhere found: North AmericaTime: Paleogene–Neogene (Oligocene–Miocene)Related genera: Archaeotherium, Choerodon

Neogene 23–presentPalaeogene 65.5–23


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PECCARIESAnother group of suiforms, which appeared in the Late Eocene(around 40 million years ago), andlived mostly in North America, arethe peccaries. They survive to thepresent as three species. Peccaries lookmuch like pigs and live in similar ways.They have large, vertical canine teeth.Some extinct peccaries, like the LateMiocene Macrogenis, had massivetriangular protrusions of bonegrowing out from their cheeks.

PIGS, HIPPOS, AND PECCARIES



Curving canineteeth withserrated edges

Big crushing molarssuggest Daeodonate bones

Elongated bonyspines grew fromshoulder vertebrae.

Powerful neck tendonsattached to the shoulderspines helped to support head.

Macrogenisskull

Daeodon

Skull bumpsbecame largerwith age.

KILLER BUFFALO PIGDaeodon, formerly called Dinohyus, is one of the biggest, best known, andlast of the entelodonts. Like others of its group, it had tall shoulders, a deep body, and long legs.The bumps on its skull and jaws were probablyused for fighting – some fossil specimens havewounds that appear to have resulted from suchbattles. The bony bumps in Daeodon were actuallysmaller than those of most other entelodonts,though they were still prominent. The teeth and muscle scars of Daeodon suggest that it wasan omnivore, easily able to break bones and eat animal carcasses. Entelodonts may havebeen scavengers, finding their food in a similar way to modern hyenas.

Unlike in smallerentelodonts, the lowerleg bones of Daeodonwere fused togetherfor strength.

Unlike in smallerentelodonts, thelower leg bones ofDaeodon were fusedtogether for strength.

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CAMELSCAMELS AND THEIR RELATIVES EVOLVED in the Eocene(56–34 million years ago), and include nearly 100 fossilspecies. Although modern camels inhabit deserts, theywere once abundant grassland and woodland herbivores.Two groups of artiodactyls – the bovoids and the camelsand relatives – evolved a special way of digesting plantmaterial called rumination. Once swallowed, food passesto the first of three or four stomach chambers, and islater regurgitated to be chewed a second time (“chewingthe cud”). In each stomach chamber, microorganismsbreak down the plant material further. Ruminantmammals recycle urea, one of the body’s waste products,and use it to feed these microorganisms. As a result, less urine is produced, and less water wasted, which is why ruminants have adapted to dry environments like deserts more successfully thanother hoofed mammals.




Stenomylusprobably livedin large herds.

Skull very shortcompared toother camels

When standingStenomylus was lessthan 3 ft 3 in (1 m)tall at the shoulder.

NARROW TOOTHThe six living camel species are native to Africa, Asia, and SouthAmerica. However, most of camel history occurred in North America,and camels still lived here as recently as 11,000 years ago. The firstcamels were small, and perhaps lived like modern gazelles. Stenomylusfrom the Oligocene (around 30 million years ago) was a small early camel with enormous chewing teeth. Unlike advanced camels,Stenomylus had pointed hooves and walked on the tips of its toes.

HIGH CAMEL

Scientific name: AepycamelusSize: 2 m (7 ft) tall at shoulderDiet: Leaves from treesHabitat: Open woodland, grassland with treesWhere found: North AmericaTime: Neogene (Miocene)Related genera: Oxydactylus, Hesperocamelus

Aepycamelus walkedon the whole length ofits toes, unlike earlierStenomylus.

Long, slenderlegs wouldhave madeAepycamelusa fast runner.

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GIANT GIRAFFE CAMELAepycamelus (“high camel”)

was a large camel withtremendously long leg and

neck bones. It was probablya browsing herbivore that,

like modern giraffes, fed from trees. EightAepycamelus species are known, each with aslightly different skull and jaws. They inhabitedgrasslands with scattered trees, and may havebecome extinct as the tree cover graduallydisappeared. Aepycamelus probably shared a number of features with living camels,including a divided upper lip, a long, curvedneck, unusual two-toed feet, and legs that arenot joined by a sheet of skin to the side of thebody. Camels also have special fanglike teeththat the males use in fighting.

FEEDING STRATEGIESLiving camels are grazers thatmostly eat grasses. The skullsand teeth of fossil camels,however, show that many of them were browsers,feeding on shrubs and trees.Oxydactylus from MioceneNorth America had longlegs and a long neck.Perhaps Oxydactylus fed on trees by standing tall on its back legs like the modernGerenuk antelope.

CAMELS



CAMEL FEET AND WALKING STYLEAdvanced camels have unique feet. Unlike otherartiodactyls, they do not walk on the tips of theirtoes, but on the whole length of their toes. Soft toepads help them walk on rocks or sand with ease.Camels walk using a technique called pacing. Bothlegs on one side of the body move in the samedirection at once.

Advanced camelslike this have onlytwo toes.

Pointedfront teethwere small.

Two “metapodial” bonesare fused together inadvanced camels.

Primitive Eocene camelsstill had four toes.

Fossil Oxydactylus foot

Feeding Gerenuk

Features of teeth andskull suggest a closerrelation to living llamasthan to modern camels.

Neck boneslonger thanthose of anyother camel

Front and back legsof camels are moreequal in size thanthey are in otherhoofed mammals.

Like living kindsof camel, fossilspecies perhapshad dense,woolly fur.

As in moderncamels, twomain handbones werefused together.

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EARLY HORNSThe deerlike protoceratids(“early horns”) lived in NorthAmerica from about 45 to 4 millionyears ago, from the Eocene to the Pliocene. Maleprotoceratids displayed some of the most spectacular and complexhorns ever evolved. In earlier protoceratids, such as Protoceras, thehorns looked most impressive in side view. Later kinds, includingSyndyoceras and Synthetoceras grew horns more suited for displayfrom the front. Protoceratids had stout limbs and bodies, andtheir teeth suggest that they ate soft vegetation and they probablyhad a flexible upper lip like a camel’s.



In the largest males,the antlers spanned12 ft (3.7 m).

Synthetoceras

DEER AND KINSEVERAL NEW GROUPS OF SMALL, forest-dwellingherbivores diversified during the Miocene(23–5 million years ago). The spread ofgrasslands allowed some of them to moveout of the forest, becoming larger andmore successful. Like bovoids, manyevolved horns or equivalent structuresfor fighting and displaying. The mostsuccessful of these mammals were thedeer – antelope-like animals distinguishedby their antlers. Early antlers weresimple in shape – any fighting wasprobably done with fanglike teeth, andsome living deer still fight in this way.Giraffids (the giraffes and their relatives)were one of the first groups to move to thegrasslands and evolve large body size. Some fossil giraffes were deerlike, and all possessed bony horns called ossicones. Several other groupsof deerlike mammals, including the paleomerycids

and protoceratids, evolved their own impressive bony horns.

Syndyoceras

Protoceras


GIANT ANTLERSThe largest antlers of all timebelong to Megaloceros, a giantPleistocene deer that was still alive9,000 years ago. Despite the hugesize of these antlers, microscopicstress marks show that they wereused for fighting and not justdisplay. Antlers are shed each yearand, except in reindeer, are grownonly by males. Antlers may havefirst developed from scar tissueresulting from injuries.

All weightwas carriedby the middletwo toes.

A dappled coat may have helpedCranioceras to hidein dense foliage.

GIRAFFIDSGiraffokeryx was a primitive giraffid that lived in Miocene and Pliocene Asia, Europe, andAfrica, around 5 million years ago. It had twopairs of pointed, furry, hornlike structures calledossicones. The giraffids are cud-chewing hoofedmammals that probably share an ancestor withbovoids. Only two survive today – the Africangiraffe (Giraffa camelopardalis) and the Okapi(Okapia johnstoni). As well as distinctive ossicones,both use a flexible tongue to bring foliage to the mouth. However, many other giraffidsthrived from the early Miocene era (around 20 million years ago) and the recent past. Onemajor group of extinct giraffids, the sivatheres,had enormous branching ossicones, and wouldhave looked more like deer than giraffes.

269

THREE-HORNED DEER RELATIVECranioceras was a paleomerycid – one of a group of deerlike hoofed mammals that lived from about 34 to 4million years ago, from the Oligocene to the Pliocene. Many,but not all, paleomerycids had bony horns that grewbackward, forward, or upward from above their eyes. In thegroup that includes Cranioceras, a third horn grew upwardand back from the rear of the skull. Healed injuries seen onpaleomerycid horns show that they were used for fighting –probably to establish mating rights and social dominance. Asin most horned mammals, only males possessed horns.While some paleomerycids hadlong limbs and probably lived inthe open, Cranioceras and itsrelatives were short-leggeddenizens of dense woodlands,about 10 million years ago. Laterpaleomerycids grew larger, butthen smaller just beforetheir final extinction.

DEER AND KIN



Limbs werenot as long orslim as thoseof grassland-dwellingrelatives.

Long rearossicones

Secondpair ofossiconeson nose

Giraffokeryx restoration

Third horncould havebeen used fordisplay as wellas fighting.

Paleomerycidhorns may havebeen more like ossicones,suggesting a close link to giraffids.

CRANIOCERAS

Scientific name: CraniocerasSize: 1 m (3 ft) tall at shoulderDiet: LeavesHabitat: Subtropical woodlandWhere found: North AmericaTime: Neogene (Miocene)Related genera: Procranioceras, Yumaceras

270

CATTLE, SHEEP, AND GOATSCATTLE AND THEIR RELATIVES arethe most plentiful large, hoofed,grazing animals alive today. Wildand domestic cattle, sheep, goats,antelopes, and musk oxen (but notthe antelopelike pronghorns) aregrouped together as bovoids, named fromthe Latin word for ox. All these animalsprobably evolved more than 20 million yearsago from small, hornless, deerlike ancestors.Early forms resembling gazelles gave rise to huge variety, with more than 100 genera by abouttwo million years ago, but all bovoids share somecommon features. These include strong, defensivehorns which never shed on the heads of bothsexes, and teeth and stomachs adapted for eatingand digesting grass. Legs and two-toed feet are alsodesigned for fast running or agile leaping to escapeenemies. The cattle family spread first throughEurope, Africa, and Asia. By one million years ago,some crossed the Bering Land Bridge into NorthAmerica where bison, bighorn sheep, and RockyMountain goats persist today.

ANCESTRAL OXBos primigenius, also known as theaurochs, was the ancestor of mostdomesticated cattle. It was larger than modern cattle, wild and fierce, and roamed the forests of Europe, Asia, and Africa, dying out in recenttimes. The last wild aurochs was killed inPoland in 1627. Bovoids such as Bos andBison priscus left large fossil horn cores ofbone. In life, horny sheaths covered thesecores, making the horns even longer.Fossils of the prehistoric ox Pelorovis,related to the modern African buffalo,have 6 ft 6 in (2 m) horn cores. With theaddition of their sheaths, its horns couldhave spanned as much as 13 ft (4 m). Theseawesome horns were used by rival males for displayand fighting, as well as for self-defense. Althoughthese prehistoric creatures are no more, wild cattleof several genera survive. The best known kinds arebison, buffaloes, and yak.

PREHISTORIC ANIMALS IN CAVE PAINTINGSAn artist depicted this great ox on a cave wall at Lascauxin southwest France some 15,000 years ago. At the time,Old Stone Age hunter-gatherers hunted wild herds ofcattle for their meat. Perhaps another 7,000 years went by before people learned to tame and farm the leastfierce individuals for meat, milk, and hides. The old wildcattle strain is now extinct, but millions of its descendantsgraze peacefully in pastures worldwide.




Jaws have high-crowned teeth, whichevolved for chewing.

Sharp, strong hornsthat are never shed

271

PREHISTORIC PRONGHORNMiocene and Pliocene North America was home to the antelopelike pronghorn or antilocaprid family, of which only onemember now survives – the second fastestmammal in the world. Ramoceros was a small,prehistoric relative of the living pronghorn.Its long, forked horns may have been usedby rival males in pushing contests. Like otherantilocaprids, Ramoceros shed the sheaths ofits horns every year, and new horns formedfrom hair sprouting on the bony cores. This difference between pronghorns and cattle persuades many scientists that these agile mammals may be more closely related to deer.

EARLY SHEEP AND GOATSGoats and sheep, includingmountain sheep like Ovis canadensisshared a common ancestor withother bovoids. This animalprobably existed in theOligocene, more than 20 million years ago. Itsdescendants gave rise first toantelopes, then to sheep andgoats, and finally to cattle.

CATTLE, SHEEP, AND GOATS

Bos stood up to6 ft 6 in (2 m) tallat the shoulder.

ANCESTRAL OX

Scientific name: Bos primigenusSize: 10 ft (3 m) longDiet: PlantsHabitat: Forest gladesWhere found: Europe, Africa, AsiaTime: Neogene (Pliocene–Holocene) Related species: Bison, Pelorovis

Muscular neckand shoulders

Hind limbs with shortthigh bones, but longshin and foot bones

Branched hornswith sheaths shedannually

Ovis canadensis skull



Sturdy limbs tosupport weight

Long footwith highankle, adesign forfast running

Foot has twolarge toes tippedwith hooves.

Tiny earlypronghornRamoceros

272


HOOFED PREDATORSWHEN SOMEONE MENTIONS “HOOFED MAMMALS,” we tend to think of unaggressive plant-eating creatures: cattle, antelope, and sheep.Early in their evolution, however, the ancestors of these even-toedhoofed mammals included very different creatures – theso-called mesonychians. Like sheep or cows, these had toes tipped with hooves, not claws. But instead ofmolars shaped for munching leaves, the creatureshad massive teeth designed for slicing meator crushing bones. Mesonychianslooked rather like, and playedthe same role as,wolves, hyenas, andbears. They livedacross Europe, Asia,and North Americafor around 30 millionyears, from the middlePaleocene (60 MYA) to the early Oligocene(30 MYA).

GIGANTIC OMNIVOREThe enormous Andrewsarchus (“Andrews’ flesh-eater”) lived in Eocene Mongolia more than 40 million years ago, and was the biggest knowncarnivorous land mammal of all time. Its skullalone was 33 in (83 cm) long and 22 in (56 cm)wide. The rest of the skeleton has not beendiscovered, but its body probably grew up to 19 ft (6 m) long or even more. Andrewsarchus’s jaws were equipped with long, sharp, curved canineteeth, and massive, crushing back teeth, powerfulenough to have killed and crunched the bones ofyoung hoofed mammals, but this enormous beastwas probably as unfussy about its diet as a grizzlybear. It would have munched juicy leaves andberries, insect grubs, and small rodents, as well asscavenging from large corpses that it came across.

POWERFUL JAWSThe skull of Andrewsarchus shows its powerful jaws andformidable collection of teeth. The canines at the front were long, curved, and piercing for delivering the killer bite to its prey. The back teeth were also pointed – the lower molarsbladelike for cutting, and the upper molars broad, designed forcrushing. Notches in the top and bottom teeth were much likethose in living carnivores, for gripping meat to tear it from thebone. The back teeth, however, were generally not as well-designed for slicing flesh as those of modern carnivores.




Andrewsarchus skull

Long, curved,pointed canine toothfor piercing flesh

Toes tippedwith shorthooves insteadof long sharpclaws

Head broad at the backwith powerful jaw muscles.

Long, narrow jaw withteeth rather like a bear’s

Massive molars with bluntcusps for crushing

273



WHALE ANCESTORSMesonychians probably became extinct when outcompeted by new kinds of more efficient predators, including the ancestors of carnivores alive today. Meanwhile, though, according to a oncepopular theory, they gave rise to a much longer-lived and moresuccessful group of mammals – the whales. The skulls and teeth of early whales such as Archaeocetes strongly resemble those ofcertain mesonychians. But other anatomical features andmolecular evidence place whales with the artiodactyls.

Long, heavy body (exact shape is unknown)

Skull shape showsMesonyx had a strong bite.

Long, lean bodyshaped somethinglike a wolf’s

HOOFED PREDATORS

Strong limbs musthave supported its great weight.

Andrewsarchus mayhave been flat-footed,like a bear.

Long, low, narrowjaws like those of mesonychians

Archaeocetes skull

ANDREWS’ FLESH-EATER

Scientific name: AndrewsarchusSize: Up to 19 ft (6 m) longDiet: Meat, plants, insectsHabitat: Scrub and open woodlandWhere found: East central AsiaTime: Paleogene (Eocene) Related species: Eoconodon, Goniaconodon

Like Mesonyx,Andrewsarchusmay have hada long tail. MIDDLE NAIL

Mesonyx (“middle nail”) was a member of themesonychids, the best-known mesonychian family. It was a wolflike predator from the Middle Eocene of Wyoming and East Asia (around 45 million yearsago). Agile limbs made it a fast runner, and it probablyhunted hoofed plant eaters, moving lightly on its toes,not flat-footed like the less advanced mesonychians. Yet,instead of claws, Mesonyx’s toes ended in small hooves.Its long skull had a crest above the braincase to anchorlarge jaw muscles and give it a powerful bite.

274

EARLY WHALESLIVING CETACEANS – whales, dolphins, and their kin –are fish-shaped, with flipperlikeforelimbs, powerful fluked tails forpropulsion, and no hind legs. Theearliest Eocene whales were very different:they had four legs and ran around on land.Yet skeletons show some had started to swimwith an up and down motion of the tail. By theend of the Eocene, fully aquatic whales likeBasilosaurus had evolved. Eocene whales werepredators that mostly inhabited shallow tropical seas.They evidently descended from close kin of, oractual, artiodactyls that had taken to foraging forfood in shallow water. Mesonychians’ skulls arestrikingly like those of the first whales, but earlywhales’ ankle bones show features only seen inartiodactyls. DNA studies even hint that whales could have arisen from the artiodactyl group that includes hippopotamuses.

FIRST WHALESThe first known whale, Pakicetus, comes from theMiddle Eocene of Pakistan, a site rich in early whalefossils. From one of these fossilized skeletons, we nowknow that Pakicetus was small – probably less than 6 ft6 in (2 m) long – and not specialized for life in water.However, its ear bones possessed features unique towhales, and its delicate front teeth suggest that itcaught fish, perhaps while paddling in shallow water.Other early whales were formidable predators –Ambulocetus looked something like a cross between awolf and a seal and had a long crocodile-like head. Itsskull was strong enough to resist the struggles of largemammalian prey.

ECHOLOCATION AT WORKThroughout their evolution, whales developeda method called echolocation to gain a mentalpicture of their surroundings. Many projectnoises through a structure on the foreheadcalled the melon. Echoes of the noises arethen transmitted to the whale’s ears via a fatty pad in its lower jaw. Eocenewhales do not appear to havehad melons though they do show evidence ofsensitive hearing.

Long tail

Large hindlimbsmade Ambulocetusa strong swimmer


Ambulocetus probablyspent most of its lifeon land, taking to theseas to hunt.



The melon sits in a large bonydepression on thetop of the skull.

Tiny, three-toedhindlimbs wouldhave projectedfrom sides.

Long tail flukesprovided the mainswimming thrust.

Square tail vertebraeshow that the tailhad flukes (finsalong its sides)

Artist’s restoration of Ambulocetus

Long skull, withnostrils close tothe tip of snout

Any nearbyobject, such asanother animal,creates an echo.


Paleogene 65.5–23 Neogene 23–present

275

EOCENE GIANTBasilosaurus is one of the biggest fossil whales known,

growing to more than 60 ft (20 m). The vertebraethat make up Basilosaurus’ back and tail

are unusual, elongated bones, unlike theshortened vertebrae seen in most whales.

These could have made Basilosaurusmore flexible than living whales.

Its huge skull, which can be more than 3 ft 3 in (1 m)

long, had curved front teethand triangular, serrated

cheek teeth. Using these,Basilosaurus could have

grabbed and sliced up fish as well

as other marinemammals.

SKULL EVOLUTIONIn early whales like Pakicetus, the nostrils were located closeto the tip of the snout, as they are in most land mammals.More advanced whales like Basilosaurus and Dorudonhave their nostrils located midway along their snouts. In

advanced whales like the Miocene Prosqualodon, thenostrils are on the top of the head where they

form the blowhole. Whales’ nostrils havetherefore gradually moved backward,

making room for the developingmelon in the forehead.

EARLY WHALES



Ribs were madeof very thick,heavy bone.

Unique long body.Other Eocene whaleswere much shorter.

BASILOSAURUS

Scientific name: BasilosaurusSize: 66–83 ft (20–25 m) longDiet: Other marine mammals, fishHabitat: Shallow tropical seasWhere found: North America, North Africa,South AsiaTime: Paleogene (Eocene)Related genera: Basiloterus Dorudon

Unlike modern whales,basilosaurs had aflexible elbow.

Prosqualodon skull Teeth of advanced whalesare all similar in shape.

Dorudon and other Eocene whaleshave two different kinds of teeth.

Dorudon skull Nostrils were notlocated on the foreheadin Eocene whales.

It is unknown whetherfossil whales haddorsal fins or not.

Wear on teeth shows thatBasilosaurus preyed onlarge animals.

276

277

Reference SectionIn this section, you can scan a pictorial summary

of life through time, with pauses for dramatic mass

extinctions. Retrace the journeys of prehistoric

creatures, from their deaths millions of years ago to

their stunning resurrection in museum halls. Along

the way, step into the shoes of a paleontologist –

spend time on an exotic dig, then learn what

goes on when fossils reach the laboratory. Watch

scientists reassemble fossil bones and see sculptors

recreate lifelike replicas of ancient animals. Get

tips on conducting your own fossil hunt. Read

about personalities who helped solve puzzles of

the past. Then discover where to see exciting

fossils on display.

278

REFERENCE SECTION

GEOLOGICAL TIME CHARTROCKS ARE DEPOSITED IN LAYERS, and the layersat the bottom of a sequence are the oldest.The actual ages in years of different rocklayers are worked out by techniques thatinvolve measuring the decay of radioactiveelements within the rock. Groups of rocklayers are classified together to form periods,

such as the Triassic and Jurassic. Periods aregrouped together to form eras, such as theMesozoic and Cenozoic. Eras are one of thebiggest subdivisions of geological time andare separated from one another by majorextinction events in which important fossilgroups disappear from the geological record.

MILLION YEARS AGO

CAMBRIAN PERIOD542-488.3

PALEOZOIC ERA

488.3-443.7 ORDOVICIAN PERIOD

MESOZOIC ERA

All major animal groups appear.

First nautiloids andjawed vertebrates.

First plants andarachnids on land. SILURIAN PERIOD443.7-416

416-359.2 DEVONIAN PERIOD

CARBONIFEROUSPERIOD359.2-299

299-251 PERMIAN PERIOD

PRECAMBRIAN4,600-542 First single-celled andmulticellular life. Collenia

Olenellus

Mawsonites

CyrtocerasOrthoceras

Baragwanathia

First vertebrates with four limbsand distinct digits.

Pseudocrinites

Pteraspis

First reptiles and flying insectson land.

Sail-back synapsidsappear on land.

EdaphosaurusDiplocaulus

Sandalodus

CENOZOIC ERA

251-199.6 TRIASSIC PERIOD

199.6-145.5 JURASSIC PERIOD

145.5-65.5 CRETACEOUSPERIOD

65.5-55.8 PALEOCENE EPOCH

55.8-33.9 EOCENE EPOCH

33.9-23 OLIGOCENE EPOCH

23-5.3 MIOCENE EPOCH

5.3-1.81 PLIOCENE EPOCH

1.81-0.01 PLEISTOCENEEPOCH

0.01-Present HOLOCENE EPOCH

First dinosaurs, mammals, turtles, and frogs.

First birds appear, dinosaurs rule the land.

First modern mammals. Non-avian dinosaurs die out.

Pterodactylus

Lystrosaurus

Proceratosaurus

Triceratops

First owls, shrews, andhedgehogs.

First horses, elephants,dogs, and cats.

First monkeys, deer,and rhinoceroses.

First apes, mice, and manynew mammals.

First cattle and sheep.Whales diversify.

First modern humansappear.

Extinctions causedby human activity.

Taeniolabis Phenacodus

Palaeochiropteryx Hyracotherium

Phiomia

Samotherium

Bison Balaena

Gigantopithecus

Homo sapiens

PAL

EO

GE

NE

PER

IOD

4,600 MYA

Formation of the Earth PRECAMBRIAN TIME

NE

OG

EN

EPE

RIO

D

COLLENIAStromatolites are layered structures that

resemble stony pillars or platforms. Theywere widespread in Precambrian times

and still exist today in Australia andelsewhere. These bizarre structures

were built by colonial microorganisms,such as Collenia, which grew in mats using

sunlight for energy. When studied under themicroscope, stromatolites can be seen to be made

up of fossil prokaryotes and other microorganisms.

279

PRECAMBRIAN TIME 4,600-542 MYA

THE RISE OF LIFEThe first living things wereprokaryotes – microscopic,single-celled bacteria-likeorganisms. They evolved in thePrecambrian, probably in the hotwater around deep-sea volcanicvents. Their fossils first appeararound 3,500 million years ago.Multicellular organisms, or eukaryotes,arose late in the Precambrian, perhapswhen single-celled forms took to living in colonies. By the end of thePrecambrian, soft-bodied animals werepresent. Some of these may be ancestorsof animals, such as jellyfish and worms,but others might be bizarre dead endsunrelated to later animals.

This timeline shows each era as a proportion of all geological time.The Precambrian era is more thaneight times longer than all the timeelapsed since.

FOSSIL TIMELINE

EARTH FACTS

The Precambrian represents morethan 85 percent of geological timeduring which the Earth changed from a molten ball to a planet with continents, oceans, and anatmosphere. The first tectonic platesdeveloped 3,800 million years agoand life evolved. Oxygen built up inthe atmosphere much later.

AQUATIC ANIMALS

EDIACARAThis simple, disk-shaped Precambrian

organism probably lived a static life on theseafloor, absorbing oxygen directly from the

surrounding water. It formed part of theVendian fauna – a group of soft-bodied organisms

first discovered in rocks in southern Australia, andlater found worldwide. Such fossils are highly

controversial because they are difficult to interpret.Scientists are not even sure if they were animals or plants.

DICKINSONIAThis 5-in (13-cm) long

segmented animal appears to have lived on or in sandyparts of the seafloor.Dickinsonia is known fromthe Vendian faunas ofAustralia and Russia. Itsidentity is controversial.Some experts argue that itwas a kind of flat-bodiedworm. Others suggest that itwas a soft-bodied coral. Oneexpert has even argued that

Dickinsonia and similar fossilswere actually lichens.

Body made ofthree connectedsegments

Round, flattenedbody, with projection at the center

542 MYA

PALEOZOIC MESOZOIC

251 MYA 65.5 MYA

CENOZOIC

TODAY

SOUTHERNGONDWANA

NORTHERN

GONDWANA

280

CAMBRIAN PERIOD

EXPLOSION OF LIFEMost of the major groups of animals that exist today evolved in the CambrianPeriod. This huge growth in diversityoccurred only in the seas – the land was still bare of life other than micro-organisms – and is called the“Cambrian explosion.” Soft-bodiedanimals and stromatolites (bacterialcolonies) of the Precambrian werelargely replaced by species with hardparts, especially trilobites. Their fossilshave been found in abundance in theBurgess Shale, a famous fossil-richarea in the Canadian RockyMountains that dates back around505 million years.

METALDETESThe appearance of shells and other hard parts was a

key event in animal evolution that occurred at thevery end of the Precambrian. Microscopic fossils

of early shelled animals are found worldwide in Cambrian rocks. They include mollusks

with coiled shells and worms that lived in straight tubes. Archaeocyathans, such as Metaldetes, had porous cone-shapedcalcite skeletons. They probably livedfixed to the seafloor.

Each body segmentsupported a walking legand a gill-bearing leg.

Metaldetes taylori

REFERENCE SECTION

XYSTRIDURATrilobites were a tremendouslysuccessful and varied group ofarthropods, and they make upone third of all fossils knownfrom the Cambrian period.Types such as Xystridura hadmany legs, complex eyesmade of numerousindividual lenses, andlong antennae. Someburrowing trilobitesfrom the Cambrian,however, lacked eyes.Other species weregood swimmers,while others couldroll into balls forprotection.

PIKAIAChordates, the groupthat includes vertebrates,evolved in the EarlyCambrian. A later kind was Pikaia,a swimming eel-like animal, 2 in (5 cm) in length. Pikaia had aflexible rod called a notochordstiffening its body. In later animals,this developed into the backbone.Pikaia swam by contracting blocksof muscle around the notochordto produce a wavelike motion.

V-shaped muscle blocksaround the notochord

AQUATIC ANIMALS

Large eyes

Metaldetes probablyresembled a modern sponge.

281

FOSSIL TIMELINE

During the Cambrian, most of theworld’s landmasses were united as the supercontinent Gondwana. Thiswas surrounded by the vast IapetusOcean. Smaller landmasses that todayform Europe, North America, andSiberia lay in tropical and temperatezones. There were no ice caps in theseas, and water levels were high.

WIWAXIAPerhaps distantlyrelated to themollusks, Wiwaxiawas 1 in (3 cm) long,dome shaped, andcovered in scales. It was equipped with longspines, probably for self-defense. Wiwaxia is fromthe Burgess Shale, but newdiscoveries show that suchanimals were widespread in the Cambrian.

MOBERGELLAAmong the early

shelled fossils of theCambrian are tiny limpetlike

forms, such as Mobergella fromScandinavia. These might not have

been separate, individual animals butscalelike structures that covered the bodies

of larger species. Members of another Cambriangroup with hard parts, the halkieriids, were elongatewith scaly bodies. It is possible that Mobergella may haveactually been halkieriid body scales.

Indentations mayhave been sitesof muscleattachment.

Ridged scale

The head shield supported largebackward-pointing horns.

Concaveinner surfaceindicates anolderindividual.

EARTH FACTS

MARRELLAThe most common

arthropod in the BurgessShale is Marella – more than25,000 specimens have beencollected to date. Up to 1 in(2 cm) long, this animal hada large head shield, and two

pairs of long antennae,although it seems to havelacked eyes. Its body was

made up of 24–26 segments,each of which carried a two-

branched appendage. Thelower branch was a walkingleg, while the upper branch

carried long gills. Theanimal was able to both

walk and swim.

Wiwaxia probablyate algae.

542–488.3 MYA

G

ONDWANA GONDWAN

A

IAPETUS OCEAN

AQUATIC ANIMALS

AQUATIC PLANTS

282

ORDOVICIAN PERIOD

FILTER FEEDERSAnother burst of evolution inthe Ordovician gave rise tothousands of new animals.Many were filter feeders thatfed on increasing numbersof plankton – microscopicfree-floating organisms – inthe water. These includedmosslike bryozoans,bivalves, and corals, whichformed reefs that were hometo swimming molluscs andother animals. Trilobitesdiversified greatly intoswimming forms equippedwith huge eyes and bottom-feeders with shovel-likesnouts for plowing throughmud. The earliest jawedvertebrates – a group thatincludes sharks and bony fish – probably also appearedin the Ordovician.

REFERENCE SECTION

ALGAE AND LIFE ON LANDColonial blue-green algae – the stromatolites – whichhad evolved in the Precambrian, were still widespreadduring the Ordovician. True algae, including globularforms that resembled sponges, lived alongside otherreef builders, such as corals, while greenalgae, the ancestors of land plants,colonized freshwater habitats.Most significantly, plantssimilar to liverworts andmosses evolved late inthe Ordovician andbegan to colonizethe land, which untilthis time had beenbarren of life. Theseplants were stillstrongly tied towater, needing itfor reproduction.

Honeycombpattern on surface of cluster

Estoniocerasperforatum

Mastopora favus

Uncoiled finalwhorl of shell

ESTONIOCERASThis swimming mollusc was a nautiloid – agroup which survives today as the animalNautilus. It had a loosely coiled shell andwas adapted for hunting in fairly deepEuropean waters, grabbing prey with itstentacles. Estonioceras was small, just 4 in (10 cm) across, but straight-shelled relatives had shells up to 16 ft

(5 m) in length. At the time, theseintelligent Ordovician predators were

the largest animals ever to have lived.

MASTOPORA This reef-forming green alga grew in

rounded clusters with a characteristichoneycombed surface pattern.

Fossils of the clusters, each about3 in (8 cm) across, are found

worldwide. Limestonesecreted by the algae coveredthe surface, protectingMastopora from hungryherbivores. Superficiallyresembling a sponge,Mastopora was originallythought to be an animal.

STROPHOMENAAmong the most abundant

of Ordovician animals werebrachiopods – filter-feeders whosetwo shells were joined at a hinge.

Strophomena was a smallbrachiopod that probably lived

on sand or mud, although manyof its relatives cemented

themselves to submerged rocks.

Shell could belocked shut byinternal pegs andsockets

283

FOSSIL TIMELINE

EARTH FACTS

The Gondwanan supercontinentremained separate from thelandmasses that would become North America and Europe, thoughthe Iapetus Ocean had started toclose. The Ordovician was a time ofglobal cooling. Late in the Period ahuge ice sheet covered much of thesouthern hemisphere.

CONODONTLong known only from their small serratedteeth, conodonts were eel-like vertebrates, or close relatives of vertebrates. With largeeyes, they probably hunted and ate smallanimals. At 16 in (40 cm) in length,Promissum, an Ordovician conodont fromSouth Africa, was the largest knownconodont. The group has a fossil record that extends from the Late Cambrian to the Triassic.

ORTHOGRAPTUSGraptolite fossils first appeared in the Cambrian,but most groups arose in the Ordovician.Graptolites formed colonies of interlinked cuplikestructures called thecae, each inhabited by a soft-bodied filter-feeding animal called a zooid. Somekinds of graptolites were attached to the seafloorwhile others floated in the surface waters.Orthograptus was a common graptolite whosecolonies consisted of two parallel strips of thecae.

Colony about 3 in(8 cm) long

Serrations onthe interlockingteeth were usedto bite and cutup prey.

ACANTHOCHONIA The surface of Acanthochonia was made up of numerous diamond-shaped cells arranged in a spiral pattern. All of thesecells originated from a single central stem, which anchored thealga to rocks or corals. The rounded alga was only about 2 in (5 cm) in diameter and lived in coral reefs.

Surface protected and strengthened by calcium carbonate

488.3–443.7 MYA

G

ONDWANA GONDW

ANAIAPETUS OCEAN

284

BIRKENIA Primitive jawless fish evolved in the Cambrian, but werestill thriving well into the Silurian. The small, spindle-shaped Birkenia lived in European lakes and rivers. Likeother jawless fish, it lacked paired fins, making it unstablewhen swimming. This poor swimmer was unable to catchfast prey and probably foraged in mud taking in tiny foodparticles through its vertical slitlike mouth. Its body wascovered by deep, overlapping scales arranged in rows. Arow of taller defensive scales grew along the top of its back.

Small body,about 3 in (6 cm) in length

Birkenia elegans

REFERENCE SECTION

AQUATIC ANIMALS

LAND PLANTS

THE PIONEERSThe Silurian marks theappearance of the firsttrue land plants,making it a critical time inthe evolution of plants. Thefirst land-living plants weremosses and liverworts thatgrew along the edges ofponds and streams. Amonglater Silurian forms werethe first vascular plants.These contained internalhollow tubes with a woodylining, which helpedsupport the plant and alsocarried water around itsbody. Because of thevessels, vascular plants wereable to grow to larger sizesand farther from water thanmosses and liverworts.

COOKSONIABest known fromSilurian rocks of southernIreland, Cooksonia was the firstupright vascular plant. Lackingleaves and roots, it was composed ofcylindrical stems that branched into twoat several points along their length. Atthe ends of the stems were cap-shapedspore-bearing structures. Compared tolater vascular plants Cooksonia was verysmall, growing to just 4 in (10 cm) inheight, and very simple in shape. Itgrew along pond and lake margins.

Branchingstemsformed Y-shapes.

Cooksonia hemisphaerica

PARKA Low-growing, liverwortlike Parka was a landplant, or maybe green alga, from Silurian andDevonian North America and Europe. It hada flattened, loosely branching shape and wasonly 2 in (4 cm) or so in diameter. A thickprotective covering on its outer surface mayhave helped prevent Parka from drying out,suggesting that it may have grown on landrather than in water.

SILURIAN PERIOD

NEW LIFEA large-scale extinction event atthe end of the Ordovician greatlyreduced the richness of animallife early in the Silurian. However,surviving groups – includingbrachiopods, mollusks, trilobites,and graptolites – soon recoveredand increased in diversity in thewarm, shallow continental seas ofthe period. Entirely new aquaticinvertebrates, such as primitive seaurchins, also appeared for the firsttime. Jawless fish still thrived whilejawed fish – including armoredplacoderms and acanthodians or “spiny sharks” – diversified,becoming increasingly important.The very first land-living animals –arthropods including millipedes,centipedes, and scorpions –evolved from aquatic ancestorsduring the Silurian.

285

FOSSIL TIMELINE

EARTH FACTS

During the Silurian, the southerncontinent Gondwana was fringed byother landmasses. Smaller platefragments moved northward andcollided, producing new mountainranges in North America and Europe.Sea levels rose as Ordovician icemelted and the climate becamewarmer and less changeable.

PARACARCINOSOMASea scorpions were Silurian arthropods –relatives of the spiders. They had long tails andmany were equipped with large pincers, whichthey used to grab and dismember their prey.Paracarcinosoma was a small sea scorpion, onlyabout 2 in (5 cm) long. It may have lived inbrackish and fresh water as well as in the sea.The squarish head, body, and its six pairs oflimbs were encased in a hard external skeleton.The last pair of limbs were paddle-shaped andwould have been used for swimming.

SAGENOCRINITESCrinoids, or sea lilies, wereimportant animals of theSilurian seas. Many speciessurvive today in deeper waters.Attached to the seafloor by long,cylindrical stalks, their tentacledheads collect plankton andsuspended food from the sea.Sagenocrinites was a small crinoidfrom Silurian Europe and NorthAmerica. Its head and tentacleswere very compact in shape,suggesting that it lived inshallower waters that wereconstantly churned by waves.

Stem covered withshort fine leaves

Abdomen

Each arm was freeand could be movedby strands of muscle.

BARAGWANATHIAClosely resembling a clubmoss, Baragwanathia was arelatively complex Silurianplant. It had branching stemsabout 10 in (25 cm) high, whichgrew upward from creeping branchesthat spread across the ground. Thestems were clothed in short leaves,giving the plant a “furry” look.Baragwanathia lived in thesouthern hemisphere and is known from Devonian as well as Silurian rocks.

BaragwanathialongifoliaParka decipiens

Distinct roundedspore capsulesgrew on itssurface.

Base of the stem attachedto the seafloor

The paired legscould have beenused for walking orfor handling prey.

443.7–416 MYA

GONDWANA

LAURENTIA

LAND ANIMALS

286

DEVONIAN PERIOD

LIMBS ON LANDThe Devonian was one of the mostimportant periods of vertebrateevolution. The first vertebrates with four limbs and distinct digits evolvedfrom lobe-finned fish during this time,and by the Late Devonian they had spread widely around the world.Land-dwelling arthropods increased in number throughout the period.Primitive, wingless insects and evenwinged forms arose while spiders andtheir relatives became more diverse.

ACANTHOSTEGAAmong the earliest of four-limbed vertebrates wasAcanthostega from Greenland. Like itslobe-finned fish relatives, it was a pond-dwelling predator that still had gills and a paddlelike tail. Its limbs suggest that it would not have been good at walkingon land. However, fossilized tracks show that some four-footed vertebrates had ventured onto land by this time.

REFERENCE SECTION

LEAVES AND ROOTSThe Devonian Period saw the most important steps so far in thedevelopment of land plants. Leavesand roots evolved independently in a number of different groups. Forthe first time, plants displayedsecondary growth – their stemscould not only grow in length, but also in diameter. Thesedevelopments allowed plants togrow far larger than before. Theearly reedlike pioneers on landgave way to gigantic trees andspecies with complex leaves.Horsetails, seed ferns, andconifer ancestors appeared late in the Devonian, and it wasthese forms that would evolveinto species that later made up the lush forests of the Carboniferous.

ARCHAEOPTERIS This widespread and highly successful

Late Devonian plant was one of thefirst to resemble modern trees. It hadan extensive root system and itstrunk had branches with reinforcedjoints at its crown. Archaeopteris wasalso one of the first plants to reachgreat size, reaching about 65 ft (20m). Scientists once thought that itswoody trunk belonged to a differentspecies and named it Callixylon.

Sharp teethsuggest a diet of fish and otheranimals.

Pointed fins with aprominent central row of bones.

Branching, fernlike leaves

Archaeopteris

DEVONIAN DIVERSITYHeavily armored jawless fishflourished in the Devonian seasand jawed fish were by now alsoabundant. Among the bony fish,lobe-finned fish were numerousand diverse while ray-finned fishbegan to become more important.Several groups of trilobites were still widespread and ammonoidsand modern-type horseshoe crabsappeared. Their descendantssurvive to this day.

AQUATIC ANIMALS

DIPTERUSLungfish such

as Dipterus wereone of the most

abundant groups of the Devonian.Five species of these lobe-finned fish

survive in modern times. Dipterus swam inEuropean waters and, like all lungfish, had largecrushing teeth. Fossilized stomach contentsshow that it was preyed on by placoderms.

LAND PLANTS

287

Zosterophyllumllanoveranum

FOSSIL TIMELINE

EARTH FACTS

The Devonian world was warm andmild. The huge continent Gondwanalay over the South Pole while modernEurope and North America werepositioned close to the equator. Sealevels were high, and much of theland lay under shallow waters, wheretropical reefs flourished. Deep oceancovered the rest of the planet.

ICHTHYOSTEGA FOSSILIchthyostega was an early four-footedvertebrate. It probably hunted fish and

other prey in shallow pools. Features of itslimbs suggest that it was relatively advanced

and was related to the ancestor of all later four-footed vertebrates. Ichthyostega had a short,broad skull and very broad ribs, which helpedsupport its body when it crawled on land.

EASTMANOSTEUSPlacoderms were jawed fish that

were abundant in Devonian seas.They included predators, armoredbottom-dwellers, and flattened ray-like forms. Some Late Devonianplacoderms reached 33 ft (10 m)in length, making them thelargest vertebrates yet to evolve.

Eastmanosteus, known fromAustralia, North America,

and Europe, was less than 6 ft 6 in (2 m) long butwould still have been

a formidable hunter.

Limbs servedas props forwalking on land.

PHACOPSThis smalltrilobite lived inwarm, shallow seas.Like many arthropods,each of its body segmentssupported two sets of limbs.For protection against predators it could roll up its body and tuck itstail beneath its head. Seven of theeight groups of trilobites, includingthe one to which Phacops belonged,died out at the end of the Devonian.

Large eye forexcellent vision

Phacops

Seven toes on each foot

Ichthyostega

ZOSTEROPHYLLUMLacking roots and leaves,Zosterophyllum was a primitive land plant. Itserect, branching stems grew not from roots,but from a complex underground rhizome(stem). The sides of the stems carried smallkidney-shaped capsules in which spores were produced. Reaching a height ofaround 10 in (25 cm), the plant probablygrew along the swampy edges of lakes.

416–359.2 MYA

GONDWANA

Clusters ofspore-bearingstems

EURAMERICA

288

CARBONIFEROUS PERIOD

ORIGIN OF THE AMNIOTESAmniotes, vertebrates whose embryos are enclosed by a watertight membrane,evolved in the Carboniferous. Both majoramniote groups – reptiles and the mammal-like synapsids – appeared at the time, whileother more primitive land-living vertebratesdiversified. At 10 ft (3 m) in length, thesynapsid Ophiacodon was one of the biggestknown land animals of the time. Flyinginsects evolved and together with arachnids– spiders, scorpions, and mites – increasedin size and diversity.

REFERENCE SECTION

LAND PLANTS

DIVERSE DEPTHSSharks and bony fishdominated Carboniferous seas, but ray-finned fish, the actinopterygians, alsodiversified greatly during thisperiod. Trilobites were stillpresent, but survived as only a handful of groups. Crinoids,brachiopods, echinoderms,and swimming mollusksinhabited the tropical coral reefs of the time.

FORESTS AND FLOODPLAINSLush tropical forests forming vastswamps and forested deltas werewidespread in the Carboniferous.Clubmosses and horsetails wereimportant components of theseforests, and some grew to immensesizes. Lepidodendron was a clubmoss130 ft (40 m) tall, while Calamiteswas a 50-ft (15-m) horsetail.Gymnosperms – the group of plants with naked seeds thatincludes conifers and cycads –began to diversify during theCarboniferous. Toward the end ofthe period, the huge European andNorth American floodplains beganto shrink as the climate became less wet. The clubmosses were then replaced by ferns and seed ferns from drier habitats.

SYMMORIUM Many of the Carboniferous sharkswere bizarre compared to modernforms. Some were decorated withpeculiar spiky crests and spines.Stethacanthus had a spine on itsback covered with toothlikematerial, while Symmoriumlooked similar but lackedthe spine. Somescientists think that it was the female of Stethacanthus.

Internal rodlike structures calledceratotrichia supported the fins.

EQUISETITESEquisetites is an extincthorsetail, which came froma group that survives todayin the form of Equisetum. It grew to a height of around 20 in (50 cm) fromunderground stems (tubers),and its straight stem carriedleaves arranged in regular ringsor whorls. Equisetites dominated the riverbanks and lake edges of the Carboniferous, and these habitats are still favored today by modern forms of Equisetum.

WESTLOTHIANA Primitive four-footed vertebrates are wellknown from fossils in North America andEurope. Westlothiana was discovered inScotland, in rocks formed in a lake fed byhot, volcanic springs. Its fossils were foundalongside those of four-legged and snake-like tetrapods as well asmillipedes, scorpions, andspiders. Westlothiana was about12 in (30 cm) long. Its longbody was carried on short legs.

Sharp teethsuggest a diet ofinsects.

Westlothianalizziae

Fossilizedtubers androots ofEquisetites

AQUATIC ANIMALS

LAND ANIMALS

Pointed teethshow thatSymmoriumwas a predator.

289

GONIATITESThis animal is a typeof swimming molluskwith a coiled shell. It was amember of a group of ammonoids(ammonitelike animals) that wasdominant throughout the Paleozoic. Like all ammonoids, Goniatites had gas-filled shell chambers that allowed it tofloat. It probably had complex eyes andbeaklike mouthparts. Goniatites lived inlarge swarms over reefs in shallow seas.

Forked tailsuggests fastswimmingspeeds.

Cordaitesangulostriatus

FOSSIL TIMELINE

EARTH FACTS

The Carboniferous is known as the“Age of Coal” because decayingvegetation from the vast forests wastransformed into coal. The mainlandmasses present were the two huge continents of Gondwana andEuramerica. Oxygen levels were high,and this may have allowed giantterrestrial arthropods to evolve.

GRAEOPHONUSArachnids, the arthropod group that includes spiders,

scorpions, and their relatives, are well represented in the Carboniferous fossil record and many new kinds made their first appearance at this time. Graeophonus was an early member of a group that survives to this day – the whip scorpions. These have six walking legs and a front pair of serrated pincers that they use to grab prey. Theylack poisonous fangs, but have sharp jaws.

CORDAITESThis coniferlike land plant grew in Carboniferousmangrove swamps,but died out in the Permian. It hadcharacteristic long, leatheryleaves and its straight main trunk grew to a heightof up to 100 ft (30 m), although other species ofCordaites were shrublike. It produced seeds in loosecones. The leaves, stems, and seeds of Cordaites hadbeen given different names because they wereoriginally thought to belong to different species.

Straplike leaves

Skeleton madeof cartilage

Two eyes on a projecting bump

Growth lines,or sutures,on shell

359.2–299 MYA

GONDWANA

EURAMERICA

290

PERMIAN PERIOD

SYNAPSIDSThe most important and diverseland-dwelling vertebrates of the Permian were the primitivesynapsids – early members of the group that includesmammals. Most were small ormedium-sized animals equippedwith powerful skulls and sharpteeth to deal with a diet of fleshor insects. They thrived, alongwith reptiles and arthropods,including spiders and insects.

Sword-shapedleaves

Glossopteris

REFERENCE SECTION

SEAS OF LIFEImmense reefs, mostly built by bryozoans (tiny, colonial animals) and sponges, teemed with marine lifein Permian times. Shelled animalscalled brachiopods burgeoned,important new fish groups evolved,and some reptiles – the mesosaurs– returned to live in water. ThePermian ended with the biggestmass extinction of all time. Manyanimals died out, although some,such as fish, were not badly affected.

NAKED SEEDSApart from lacking flowering plants, Permian plantcommunities resembled some that thrive today. Theclubmosses and horsetails that had formed the vastCarboniferous forests largely disappeared and were replaced by gymnosperms, plants that produce theirseed “naked,” not enclosedin a fruit. Conifers(gymnosperms withneedlelike leaves)flourished and two othergymnosperm groups –cycads and ginkgos – alsoevolved. Late in thePermian, many of theconifers developed thickfleshy leaves protected byhairs. These features helpedthe plants to tolerate thehot and dry climate thattypified Late Permian times.

EDAPHOSAURUSThis Permian synapsid had a broad, rounded body with

a tall fin on the back. This fin was richly supplied withblood vessels and so couldabsorb or radiate heat. It

may have been used to controlthe animal’s body temperature.Edaphosaurus had two types of

teeth. Peglike teeth lined its jawsand crushing teeth were locatedon its palate. These featuressuggest that it was a herbivore that fed on ferns and other tough Permian plants.

DERBYIABrachiopods were shelled, filter-feeding

animals that evolved in the Cambrianand still survive today as lamp shells.

Their larvae could swim, butadults lived a static life on the sea floor. Derbyia was a large,heavy brachiopod that grew to 3 in (8 cm) in diameter in the Carboniferous andPermian seas. Brachiopods were plentiful in the Devonian, but there were few left by the end of the Permian.

GLOSSOPTERISOne of the mostimportant Permiangymnosperms wasGlossopteris. This tree,which grew to 26 ft (8 m), and its closerelatives dominated the southern part of thesupercontinent Pangea.Fossils of Glossopteris have animportant place in scientific history. They were found across all thesouthern continents, thereby providing one of the first pieces of evidence tosupport the theory of continental drift.

Fragment ofpalate with teeth

LAND ANIMALS

AQUATIC ANIMALS

LAND PLANTS

291

DIMETRODON A stout skull and large, pointed

teeth made Dimetrodon anawesome predator. This fin-

backed synapsid grew toaround 10 ft (3 m) inlength. It had lightly builtlimbs so could run fast to catch its prey. Animalslike Dimetrodon were

important because theygave rise to an entirely

new group of synapsids, the therapsids, which becamedominant in the late Permian.

FOSSIL TIMELINE

The two major landmasses of theearly Permian – Euramerica in the north and Gondwana in the south –collided late in the period to form the supercontinent Pangea. ThePangean climate became hotter and drier. While the south seems to have been relatively cool, tropicalconditions prevailed in the north.

PALEONISCUMRay-finned fish, which evolved in the Devonian, continued to diversifyduring the Permian, and a major new group – the neopterygians –appeared. Paleoniscum was a primitiveray-finned fish distantly related tothe neopterygians. It grew to around8 in (20 cm) in length. Covered by a coat of overlapping scales, this spindle-shaped predator was a strong swimmer.

MARIOPTERISFound in late

Carboniferous and early Permian swamps,Mariopteris grew to aheight of around 16 ft(5 m). Its stem consistedpartly of old leaf bases.Some species weretreelike, while otherswere climbing plants.

EARTH FACTS

Mariopteris maricata Small, pointedleaflets

Eye socket

Paleoniscum magnus

Dimetrodon loomisi skull

Long, streamlined bodysuited to fast swimming

Asymmetric tail fin

299–251 MYA

P A N G E A


292


REFERENCE SECTION


PERMIAN EXTINCTIONTHE END OF THE PERMIAN PERIOD, 251 million years ago, sawthe greatest mass extinction of all time, a period of crisisthat has been called “the time of great dying.” Perhaps asfew as five percent of all species survived. In the seas, reef-dwelling animals were severely affected and trilobites, seascorpions, and key coral groups disappeared. On land,many synapsid and reptile groups vanished. Some experts think that the Permian extinction happenedquickly, but it seems unlikely that a single catastrophe was responsible. It is more probable that a series of several events gradually resulted in the mass extinction.The formation of the supercontinent Pangea, for example,would have destroyed important shallow coastal seas andcoastline habitats. Climate changes and volcanic eruptionsundoubtedly contributed to the extinction.

CLIMATIC CRISISClimate change characterized the end of the Permian. Rocks from theperiod indicate that cooling occurred in some areas and ice sheets builtup at the poles, causing the global sea level to drop. The white icesheets reflected sunlight back into space, lowering global temperatureseven further. Falling sea levels may have exposed huge areas of coal onthe seafloor. This would have released large amounts of carbon dioxideinto the atmosphere, so reducing oxygen content. Less oxygen in theatmosphere may have contributed to the extinction of animals withactive lifestyles, such as the mammal-like synapsids.

DESERT DEVASTATIONWhen the Permian landmasses

collided, they produced the vastcontinent of Pangea. Rainsand mists that arose at seacould no longer reach theinterior of the land, with theresult that some parts of thePermian world became drier

and hotter. Deserts grew everlarger, and animals not adapted

for life in the arid conditionsbecame extinct.

Brachiopods likeEdriostege, grewon the tops ofthe reefs.

Branching coloniesof bryozoans, ormoss animals

FIERY ENDA possible cause of the end-Permianextinction is volcanic activity. Hugeeruptions of volcanic material are known to have happened in Siberia at this time.Around one million cubic miles of lavapoured out, covering enormous areas ofthe land surface, and pumping vastamounts of gases and dust into the air.This volcanic dust blocked the Sun’s rays,causing the air to chill. Then, later, as dustsettled, carbon dioxide trapped so much ofthe Sun’s heat that temperatures soaredwith lethal effects.

Rugose coralscompletelydisappeared in the Permianextinction.

293



FOSSIL TIMELINE

DEATH OF A REEFA Permian coral reef is shown healthy on the left-hand side of the image – anddying as it would have appeared duringthe Permian extinction – on the right-hand side. Permian reefs – complexenvironments built by corals and sponges – were inhabited by thousands of different animals and plants. Loweredsea levels and reduced areas of shallowseafloor that resulted from the formationof Pangea destroyed the areas in whichreefs could grow. The reefs weregradually killed off, causing an enormous drop in the diversity of marine life. Reduced quantities of oxygen in the Permian atmospherewould also have meant that sea watercontained less oxygen than before. Entire oceans would have slowly become stagnant, suffocating the life they contained.

Reef animalswould have diedoff as oxygenlevels in the seadropped.

The hugetubular spongeHeliospongiawas one of thelargest reeforganisms ofthe Permian.

Gastropodsgrazed on algaethat grew onthe reefs.

CYNOGNATHUS This aggressive Early Triassicpredator was a member of thecynodonts – a group of advancedsynapsids. Growing to 6 ft 6 in (2 m) in length, it possessedprominent canine teeth, shearingcheek teeth, and large jaw musclesthat allowed it to hunt other largesynapsids. It may have been warm-blooded and fur-covered like amammal, and its close relatives were themselves the ancestors of mammals.

294

TRIASSIC PERIOD

THE AGE OF REPTILESThe Triassic was the start of the “Age of Reptiles” and a time whenanimals from very different lineageslived alongside one another. Synapsidrelatives of the mammals, were stillimportant but were gradually beingdriven to extinction. Archosaurs, the“ruling reptiles,” became important andthe first crocodylomorphs, pterosaurs,and dinosaurs all arose late in theTriassic. The first turtles, frogs, andmammal-like animals also appeared.

REFERENCE SECTION

LAND PLANTS

SEA CHANGEModern-type corals formedthe Triassic reefs and newgroups of ammonoidmolluscs appeared.Advanced ray-finned fishand the first modern sharksand rays replaced slower,older kinds of marine life.Primitive ichthyosaurs evolvedand soon became dolphin-shaped predators. Some were as big as modern whales.

DOMINANT CONIFERSMost plants of the earlierPaleozoic Era reproduced byspores and so relied on moisthabitats to reproduce. Thesegroups – including the famousglossopterids of the southerncontinents – suffered in thedrier conditions of the Triassic,when the landscape wasincreasingly dominated byevergreen trees (conifers andother gymnosperms). Amongthe more modern kinds ofplants, cycads became wellestablished. Ginkgos – relativesof the conifers – became moresuccessful and at least sevengenera, including the moderngenus Ginkgo, lived duringTriassic times.

GINKGO This tree, which evolved in theTriassic, survives essentially unchangedto this day. A native of China, it hasbeen transported around the world forplanting in urban parks and gardens,partly because it grows well in heavilypolluted air. Ginkgo grows to around 115 ft(35 m) in height. It is deciduous, and thereare abundant fossils of its leaves. Membersof the Ginkgo genus typically grew in damphabitats in temperate climates.

Diamond-shapedscales covered the streamlined body.

LAND ANIMALS

AQUATIC ANIMALS

DICELLOPYGEPrimitive ray-finned fish like

Dicellopyge were importantpredators in the Triassic. This

small freshwater fish from southernAfrica had a deeply notched tailsuggesting that it was a fast swimmer.Its deep skull and jaws were armedwith conical teeth that allowed it tocatch and eat smaller fish andswimming invertebrates.

Leaf fossilizedin mudstone

Ginkgobiloba leaf

295295

Enlarged, stabbingcanine teeth

FOSSIL TIMELINE

The vast supercontinent of Pangeastraddled the equator during theTriassic. Hints that it would later splitup came from the narrow seaway thatseparated North America fromEurope and another tongue of sea,the Tethys, which encroached onEurope. The climate was generallywarm and dry.

MEGAZOSTRODON One of the earliest of all

mammaliaforms, Megazostrodon, wasonly about 5 in (12 cm) long andlived in Africa, although similar

forms inhabited Europe and Asia.Like other early mammals, it was

probably nocturnal andresembled a modern shrew in

appearance and lifestyle. Its teethand jawbones suggest that it

hunted insects and other smallanimals and hid in burrows. As in

later mammals, some of itsjawbones formed

parts of its ear.

NEUSTICOSAURUSThe sauropterygians were a group of marine reptilesthat evolved during the Triassic. The most famous

members of the group were the plesiosaurs.Neusticosaurus was a small, amphibious, predatory

sauropterygian that lived in the shallow seas of TriassicEurope,. where it hunted invertebrates and fish. Fossils

of babies preserved without eggshells suggest that thesereptiles may have given birth to live young.

Small,delicatebones

Deep jaws couldhold struggling prey.

Limbs wereused aspaddleswhen in the water.

EARTH FACTSThick, heavy ribs helped keepNeusticosaurus submerged.

PACHYPTERISSeed ferns (pteridosperms),such as Pachypteris, were notferns at all, but primitiveseed plants that lived inswampy areas. They hadwoody stems studdedwith dried-out leaf bases.Their tops had fernlikefronds that carried theseeds. The group wasvery successful late inthe Paleozoic, but graduallydeclined in importance during theMesozoic, finally becoming extinct in the Cretaceous. Pachypteris, which grewworldwide in tropical forests, was one of thelast seed ferns to die out in the Cretaceous.

Typical height 6 ft 6 in (2 m)

251–199.6 MYA

PANGEA

TETHYSOCEAN

296296

JURASSIC PERIOD

RULE OF THE DINOSAURSLife on land took on a very differentappearance in the Jurassic. Mostcrocodile-group archosaurs andsynapsids were wiped out at theend of the Triassic (but some smallsynapsids, including early mammals,survived). Giant dinosaurs took over asthe dominant animals. On land, platedstegosaurs and long-necked sauropods werepreyed upon by large theropods. In the air,new kinds of pterosaurs were seen and the firstbirds evolved from small predatory dinosaurs.

REFERENCE SECTION

JURASSIC DIVERSITYImportant marine animals that appeared inthe Jurassic include ammonites, belemnites,and modern-type sharks and rays. Teleosts –bony fish – diversified greatly into long-bodied predatory forms as well as giganticfilter-feeders, which may have been thebiggest fish of all time. Crinoids,relatives of today’s sea lilies, wereimportant during the period.Giant forms, some with stalks aslong as 50 ft (15 m), grew fromfloating driftwood.

THE AGE OF CYCADSCycads, conifers, and ginkgos wereimportant Jurassic plantgroups. So many cycadsgrew in the forests of thetime that the Jurassic isoften called “the Age ofCycads.” One group ofcycadlike plants – thebennettitaleans – weresignificant because they mayhave been the ancestors of floweringplants. Jurassic conifers included close relatives of living pines, yews,redwoods, and cypresses. Fernsformed much of the ground cover,and all three major fern groups hadprobably evolved by the Jurassic. Clubmosses, horsetails, and seed fernscontinued to survive but were not as important as in earlier times.

CYCASCycads are gymnosperms that reachedtheir greatest diversity and abundanceduring the Jurassic. Cycas, of which

about forty species survive today, firstappeared in the Jurassic. Some

species grew into giant tree-like forms, while others weresmaller and more fernlike.Jurassic cycads lived

worldwide, but today’sspecies are restricted to

the tropical andsubtropical zones.

PTERODACTYLUSPterosaurs were reptiles that

developed wings and poweredflight. They evolved in the Triassic

and diversified during the Jurassic,when shorter-tailed, longer-wingedforms appeared. Pterodactylus was asmall Jurassic pterosaur that livedalong shorelines, feeding on fish andcrustaceans. Just 12 in (30 cm) long, ithad a lightly built skeleton and thin,hollow bones. Its wing membrane wassupported by the long fourth finger.

ICHTHYOSAURUSAdvanced ichthyosaurs (“fish lizards”), swimming crocodylomorphs, andnew kinds of plesiosaurs all added to the diversity of marine reptiles in the Jurassic. Ichthyosaurus was a European fish lizard. It had large, sensitive

eyes and a slim snout containing many cone-shaped teeth, bothof which helped it catch fish and swimming mollusks. There

were several species of Ichthyosaurus ranging in size from 3–10 ft (1–3 m) long.

AQUATIC ANIMALS

This specimen preserves its wingmembranes, throat pouch, and foot webbing.

Cycas frondsmade of manyparallel leaflets

Nostril waslocated close tothe eye socket.

Ring of bony plates

Many cycadleaves werepoisonous.

Slender clawed toes

LAND ANIMALS

LAND PLANTS

297297

196.6–145.5 MYA

Long hind limbswith four toes

FOSSIL TIMELINE

The Pangean supercontinent split asthe Atlantic opened up between theareas that today form Africa andNorth America. The land that wouldlater become Antarctica, India, andAustralia started to move away fromthe rest of Pangea. The climate waswarm, and, with no polar ice caps, sealevels were high worldwide.

COMPSOGNATHUSThe chicken-sized

Compsognathus was anadvanced predatory dinosaur

from Late Jurassic Europe. It walked on its two long, slim

hind limbs and probably stalked its prey of small lizards and insects. It was similarin size, habit, anddistribution to the birdArchaeopteryx, and thetwo may have lived side-by-side in the woodlandsof southern Germany.

EARTH FACTS

ARCHAEOPTERYX Perhaps the first true bird,Archaeopteryx evolved in theJurassic from small theropodancestors. It retains manyfeatures of its reptile past –three working fingers, trueteeth, and a breastbonewithout a keel. This famousfossil – known as the Berlinspecimen – was discoveredin the Solnhofen limestonesof Germany in 1877.Remarkably, it preservescomplete impressions of thewing and tail feathers.

Serrated teeth in lightly built skull

ASPIDORHYNCHUS Among the new Jurassic teleosts were long-

bodied predators, such as Aspidorhynchus.Growing to around 20 in (50 cm) in length, it

had a pointed skull, large eyes, and sharpteeth. Its upper jaw was extended beyond the

lower jaw, forming a prominent toothless“beak.” Its tail was symmetrical, and thick

rectangular scales protected its body.Aspidorhynchus was widely distributed in

shallow, subtropical seas.

WILLIAMSONIAThis plant, which livedthroughout theMesozoic, was a memberof the Bennettitales – agroup that may include

the ancestors of floweringplants. It had a robust stem

that was covered in diamond-shaped scales and grew large

flowerlike structures. TheBennettitales had leaves that

resembled those of cycads, and were probably related

to this group.

Flowers probablypollinated by insects

Triangular skullwith forward-facing eyes

Williamsonia

PAN

GEA

TETHYSOCEAN

298298

CRETACEOUS PERIOD

NEW DINOSAURSDinosaurs remained the dominant landanimals during the Cretaceous. Newgroups, including tyrannosaurs, duck-billed hadrosaurs, and horned dinosaurs, spread across the northerncontinents, while birds evolved fromtoothed Archaeopteryx-like species intoforms that resembled modern kinds.Snakes developed from lizard ancestorsand new groups of insects, includingmoths, ants, and bees, appeared feedingon and pollinating the newly evolvedflowering plants.

ZALAMBDALESTESEarly Cretaceous mammals were small and

insignificant, just as they had been throughoutthe Triassic and Jurassic, but an important new

group emerged later in the Period. Characterized bythree-cusped teeth, this group included Zalambdalestes,which probably resembled a modern elephant shrew.

Zalambdalestesprobably fed on insects

Betulites

REFERENCE SECTION

AQUATIC ANIMALS

MESOZOIC MARINE REVOLUTIONMarine invertebrates took on a distinctlymodern look during the Cretaceous. Crabsand other modern crustaceans appeared, as did predatory gastropod mollusks andburrowing sea urchins. Among fish, theteleosts (advanced bony fish) underwent amassive increase in diversity and relatives ofmodern herrings, eels, carps, and perchesall appeared. Swimming lizards calledmosasaurs and the first marine turtles and aquatic birds also evolved.

FLOWER POWERCretaceous forests were largelydominated by several groups ofgymnosperms, particularlyconifers, including cypresses,bald cypresses, and monkey-puzzle trees. Othergymnosperm groups, such ascycads and ginkgos, declinedin importance. Floweringplants – the angiosperms –arose, first as small, weedlikeforms in areas of landdisturbed and trampled byherds of dinosaurs. Later in theperiod, flowering plants,including birches, willows, and magnolias, formed forestsin which the dinosaurs lived,but ferns remained importantwherever rainfall was high.

MACROPOMA Coelacanths – fleshy-finned fish that first appeared in the Devonian – grew to sizes of up to 10 ft (3 m) inCretaceous seas, though the group was in decline later inthe Period. Macropoma was a European coelacanth, lessthan 24 in (60 cm) long. It had a short, deep body andlarge fins that would have aided maneuverability. Its tailhad three lobes – a feature common to all coelacanths.

Stiff tail helped balancethe heavy body.

Leaf fossilin ironstonenodule

BETULITES Betulites is an extinct member of the birch family, and a close

relative of Betula, the familiar modern birch tree. Likeliving birches, it grew in temperate climates,

favoring lakesides and other damp habitats. Betulites had round or oval

leaves that had teeth along theirmargins – typical of plants that grow

in cool or dry environments. Because fossilized Betulites leavesare frequently detached fromtwigs, this tree was probablydeciduous.

Mobile skulljointallowed jaws toopen wide

LAND PLANTS

LAND ANIMALS

299

FOSSIL TIMELINE

EARTH FACTS

CORYTHOSAURUS Among the mostcommon Cretaceous

dinosaurs werehadrosaurs – the

duck-billeddinosaurs – which

evolved fromIguanodon-like ancestors. With batteriesof chewing teeth and powerful jawsthey were successful browsing

herbivores. Crested hadrosaurssuch as Corythosaurus hadhollow bony crests on theirheads, which may havehelped amplify their calls.

PROTOSTEGATurtles first evolved in the Triassic,

but forms specialized for life atsea, such as Protostega, did notappear until the Cretaceous.

Unlike land-dwelling turtles, thesehad flipper-like limbs. Glands neartheir eyes allowed them to excrete

excess salt taken in with theirfood. Some relatives of Protostega

reached lengths of 17 ft (5 m)and like today’s sea turtles, they

probably ate jellyfish, marineplants, and sponges.

Lower hipbonesprojectedbackward.

Hollow creston head

Large,powerfullymuscled legs

Flippers werewell-muscled forfast swimming.

Ribs supported a rubbery skinover the turtle’sback.

ONYCHIOPSISFerns were important low-growing plantsthrough much of the Mesozoic but theybecame less widespread as floweringplants increased in importance duringthe Cretaceous. Onychiopsis, a small fernfrom the northern hemisphere haddelicate, feathery leaves. It reachedabout 20 in (50 cm) in height and likeall ferns required damp conditions toreproduce. It probably grew around

lakes and in shelteredforest environments

amongst largerferns and cycads.

Onychiopsis psilotoides

Spore capsuleswere carried onthe fronds.

145.5–65.5 MYA

Continents began to take on familiarpositions during the Cretaceous. Bynow Pangea had split into Laurasiaand Gondwana. These continentswere themselves breaking apart intothe continents that exist today.Madagascar and India separated fromGondwana and moved north. Largeinland seas covered parts of Laurasia.

TETHYSOCEAN

LAURASIA

G

ONDWANA

300


REFERENCE SECTION



LAST SURVIVORSScientists are unsure how many dinosaurs were alive at theend of the Cretaceous. It is possible that many species hadalready become extinct by this time. If so, the whole groupwas very vulnerable to being wiped out by an extraordinaryevent, such as asteroid impact. Triceratops andTyrannosaurus were among the last of the dinosaurs, but many animal groups survived, including insects, some mammals, crocodiles, lizards, and lissamphibians on

land, and many fish andinvertebrate groups

in the sea.

THE END OF THE CRETACEOUS PERIOD, 65.5 million years ago, saw the mostfamous mass extinction event of all time – although it was certainly not thebiggest in terms of species lost. All large land animals disappeared, as didnumerous marine invertebrate groups. The theropods – flesh-eatingdinosaurs – survived as birds, but all other dinosaurs became extinct. In the seas, plesiosaurs and mosasaurs died out, as did many kinds ofbivalves, swimming mollusks, and plankton. Some evidence indicates that alarge asteroid struck the Earth at this time. Experts speculate that such animpact would have thrown up enough dust to block out light from the Sunfor years or even decades. Perhaps this prolonged cold, dark phase causedCretaceous plants and animals to die off. However, changes in Cretaceousclimate and sea level may already have sent some groups into decline.

END OF THE DINOSAURS

The last dinosaursmay have inhabiteda burnt, pollutedworld with littleremaining plantgrowth.

301



FOSSIL TIMELINE

METEOR EVIDENCEIn 1980, scientists found high levels of themineral iridium in layers of end-Cretaceousrock. Rare on Earth, iridium is common inasteroids, so the scientists suggested that itspresence could be accounted for by anasteroid impact. In 1990, evidence of such animpact – a crater 120 miles (200 km) wide –was found off the coast of Mexico. Named theChicxulub Crater, it was made by an asteroidaround 6 miles (10 km) wide. The similarcrater shown here is from much youngerrocks in Arizona.

AFTER THE ASTEROIDMany kinds of environmental damage would have followedthe impact of the Chicxulub asteroid. This damage couldhave contributed to the extinction of the dinosaurs andother animals. The impact would have thrown up tidalwaves that would have washed ashore on the NorthAmerican continent, destroying coastal habitats. Hot debristhrown into the atmosphere by the impact may later haverained down to Earth and started huge wildfires.

Triceratops wasone of the very last nonaviandinosaurs.

302

PALEOCENE AND EOCENE EPOCHS

LARGE LANDLUBBERSAt the start of the Paleocene, there were nolarge animals on the land. Soon the worldbegan to be repopulated by large mammals –which developed from small survivors of theCretaceous extinction – and by hugeflightless birds. Bats, rodents, and trueprimates made their first appearance,together with many bird groups, includingowls, swifts, herons, and eagles. Crocodiles,lizards, turtles, and frogs thrived in thetropical Eocene world, and snakes increasedin diversity, feeding on the new rodent types.

Nipa burtinii

REFERENCE SECTION

LAND ANIMALS

AQUATIC ANIMALS

SEA MAMMALSModern forms of marine lifebecame firmly established in thePaleocene and Eocene. Fish tookon now-familiar forms and newgroups of barnacles, crustaceans,and mollusks evolved. Earlypenguins diversified, and giant forms up to 5 ft (1.5 m) tallinhabited the southern seas.Mammals also took to aquatic lifeas the first whales and the plant-eating seacows evolved.

TROPICAL TIMESThe Paleocene and Eocene world wasdominated by tropical forests. Even Europe washome to tropical swamps where ferns, horsetails,and palms formed the forest understory andvines and citrus trees grew overhead. Paleocenetrees included forms as diverse as hazel,chestnut, sycamore, alder, magnolia, poplar, and walnut. Trees including beech and sequoiaswere also present at the time. These formswould later become more important in thetemperate forests of the Miocene and beyond. Toward the end of theEocene, the world cooled. Asa result, deciduous andconiferous trees becamedominant at higherlatitudes, and tropicalforests retreated to theequatorial regions.

WETHERELLUSThis Eocene mackerel was around 10 in (25 cm) in length. Mackerels are fast-swimming marine fish that belong to a group called the scombroids,which are more streamlined thanany other group. Swimming inschools, they feed on smallerfish and crustaceans.Some scombroids haveheat-generating organs intheir eyes and brains thatallow these parts of their bodies to function well at low temperatures.

NIPA This palm, which survives today

only in the mangrove swamps of southeast Asia, grew over

large areas of the NorthernHemisphere in the Eocene.Palms are flowering plantsthat belong to the samegroup as grasses, orchids,and lilies. They have leaveswith parallel veins and their

germinating seeds grow oneinitial leaf (rather than two).

Unlike more typical palms, Nipadoes not have a true stem. Its

coconut-like seeds grow at its base.

PALAEOCHIROPTERYXBats probably evolved from tree-climbing ancestors that leapt tocatch their insect prey. Early truebats, such as Palaeochiropteryx fromEocene Europe, had wingsformed from enlarged hands.Though their wings were lessadvanced than those of modernspecies, their earbones show thatthey were already using highfrequency calls to locate prey.Like modern bats, they wereprobably nocturnal, highly agilefliers that fed on flying insects.

Rounded Nipa fruit withprotective woody shell

LAND PLANTS

Wide jaws linedwith rows ofpointed teeth

303303

GASTORNISPreviously known as Diatryma,Gastornis was a giant, flightless, landbird of Paleocene and Eocene NorthAmerica and Europe. It stood 7 ft (2.1 m)high and had short, largely useless wings, butits long, stout legs would have made it a fastrunner and powerful kicker. Its massive, deepbeak was very powerful, suggesting that it couldbreak open bones. Some features indicatethat Gastornis was most closely related toducks, geese, and their relatives.

FOSSIL TIMELINE

Tropical forests thrived duringPaleocene and Eocene times, even at the poles, but the climate cooledlate in the Eocene. North Americaand Europe were still linked, but aseaway separated Europe from Asia.India and Africa were isolated islandcontinents, while Australia broke awayfrom Antarctica late in the Eocene.

BASILOSAURUSOne of the best known fossil whales is Basilosaurus, agigantic long-bodied predator from the shallow Eocene

seas of the northern hemisphere. It grew to more than66 ft (20 m) in length and had a huge skull with

massive grabbing and slicing teeth. Likemost other primitive whales, it had

small hind legs with a workingknee joint and small, three-

toed feet. Relatives ofBasilosaurus were ancestorsof the modern whales.

Large brain,though smallerthan that of living whales

Masses of bloodvessels helpedcontrol braintemperature.

EARTH FACTS

FICUSFicus, the figs, are widespread flowering plants and are

part of the same group as oaks. Their fossils firstappear in Eocene rocks. Some types of fig grow as shrubs or trees that can reach 100 ft (30 m)

in height while others are climbers.Strangler figs are parasites that use

trees for support as they grow,eventually killing them. Fig

seeds are rounded and growsurrounded by fleshy fruit.

Figs were animportant food forfruit-eating animals.

Ficus

Beak well suitedfor crushing

Ficus fruit withwoody covering

65.5–33.9 MYA

SOUTHAMERICA

NORTHAMERICA

AFRICA

ASIA

INDIA

ANTARCTICA

AUSTRALIA

EUROPE

AEGYPTOPITHECUSThis primate lived inEgypt and was amongthe first members ofthe Old World monkeygroup. About the sizeof a domestic cat, itresembled a modernmonkey and probablyclimbed in trees feedingon fruit and leaves. Compared to its earlier ancestors,Aegyptopithecus had fewerteeth, a larger brain, and more forward-looking eyes.

304

THE MODERN AGEMany essentially modern animalsevolved during the Oligocene and Miocene. Monkeys and apesreplaced primitive primates, andsome African monkeys crossed the Atlantic to colonize SouthAmerica. As grasses spread,mammals emerged that resembledtoday’s grazers, such as horses,elephants, and camels. Modernforms of carnivores, birds, lizards,snakes, and frogs also arose.

REFERENCE SECTION

FAMILIAR WATERSBy the Miocene, well-known typesof fish such as mackerels, flatfish, and advanced sharks,including the Great White, swamthe seas, while carp, catfish, andother groups evolved infreshwater. Modern whalesdeveloped in the Oligocene, andthe first seals evolved from bear-like ancestors. The lattercompeted with giant diving birds,hastening their extinction.

TEMPERATE LANDSDuring the Oligocene and Miocene,the tropical forests of the Eocenegradually gave way to driergrasslands. First, the lowertemperatures of the Oligocenerestricted tropical forests andallowed temperate woodlandsconsisting of broad-leaveddeciduous trees to spread across thecontinents. Then the warmer anddrier conditions of the Miocenecoincided with the evolution ofgrasses – ground-hugging plantsthat could grow with little water.The grasses spread across thelandscape, forming vast savannah and prairie environments in thesouth. Temperate forests of conifers,oaks, birches, elms, and willowsremained in the north.

HIPPARION Horses had existed since theEocene, but only with thespread of grasslands in theMiocene did they emerge asimportant large-bodiedherbivores. Unlike theirforest-dwelling ancestors, newhorses like Hipparion hadlonger limbs and high-crowned teeth that allowedthem to feed on the toughnew grasses.

ACER The maples (Acer) and their relativesfirst evolved in the Oligocene, andmany species survive today intemperate forests around the world.All are deciduous trees, some of whichgrow to 82 ft (25 m) in height. Mapleleaves are three-lobed with long stalks.Flowers are produced indrooping clusters and arefollowed by distinctivewinged fruits. Thewings allow the fruit tobe caught by the windand carried longdistances from the parent tree.

Wing of Acerfruit preserved in limestone

LEUCISCUSThe fish Leuciscus appeared in theOligocene and survives to this day inNorth America, Asia, Europe, andAfrica. It inhabits freshwater streamsand pools, where it uses its specializedtoothless jaws to feed on aquaticplants. Like other members of thecatfish–carp group, Leuciscus hasspecial ribs that transmit vibrations

from its swim bladder to its inner ears,providing it with sensitive hearing.

AQUATIC ANIMALS

LAND PLANTS

LAND ANIMALS

Body around 4 in (10 cm) long

These Leuciscus probably diedas their home lake dried up.

Leuciscus pachecoi

OLIGOCENE AND MIOCENE EPOCHS

Acer

305305

FOSSIL TIMELINE

During the Oligocene, South Americaseparated from Antarctica, allowingocean currents to move aroundAntarctica for the first time. TheAntarctic ice cap now began to form,cooling the climate. By Miocene times,India had collided with mainlandAsia, causing the Himalayas to rise.Africa also connected with Eurasia.

PALAEOCASTORRodents were abundant from the start of theOligocene and diversified throughout the period.Early squirrels, mice, and porcupines emerged, asdid beavers like Palaeocastor. This burrow-dwellinganimal lived on the plains of North America anddug distinctive corkscrew-shaped burrows. Itprobably resembled a modern marmot.

PACHYDYPTESPenguins, flightless marine birds that

evolved from close relatives of albatrosses,appeared in the Eocene and continued to

be successful throughout the Oligoceneand Miocene. All forms lived in the

Southern Hemisphere. Pachydyptes, a giant penguin from New Zealand, was similar in

appearance to living penguins and, like the modern forms, fed on fish

caught underwater.

Limbs well-suited fordigging

Stout upperarm bone

EARTH FACTS

Hipparion had along, slim skull andhigh-crowned teeth.

Largechewingteeth

QUERCUSThe oak, Quercus, is one of the mostdistinctive of largetrees and is animportant component of many temperate forestenvironments. Quercus is awidespread and diverse genus, which firstappeared in the Eocene. Some forms have lobedleaves. Some are deciduous, others evergreen. Asshown in this Miocene tree trunk, their woodbears distinctive growth rings.

Color caused bymineral impurities

Species ofQuercus canreach 130 ft (40 m) in height.

33.9–5.3 MYA

Quercus

ANTARCTICA

SOUTHAMERICA

EURASIA

INDIAAFRICA

AUSTRALIA

NORTHAMERICA

BALAENA The right whale, Balaena, whichgrows to 65 ft (20 m) in length,

has been hunted to nearextinction by humans. Its

enormous mouth has long, finebaleen plates that are used tofilter food from seawater. Like

all advanced whales, it has a shell-shaped ear bone connected to

the skull by ligaments. After death,the ear bone often drops away

from the carcass.

306

PLIOCENE EPOCH 5.3–1.81 MYA

GRASSLAND GRAZERSPliocene animals were largelysimilar to today’s forms. Hoofedmammals, such as one-toedhorses, camels, elephants, andantelopes became more diverseas they exploited the newlydeveloping grassland habitats.Large saber-toothed cats huntedthe plains and forests of theAmericas, Africa, Asia, and Europeand the first humans evolved fromchimplike ancestors.

TETRALOPHODON Elephants appeared in thePaleocene, but during the Miocene

and Pliocene advanced forms, closelyrelated to today’s species, spread to

most parts of the world. Tetralophodonwas an elephant that lived in Africa, Asia,

and Europe. It had a long skull but, unlikeliving elephants, sometimes possessedlower jaw tusks. Tetralophodon may have been one of the first members of theElephantidae, the group to whichmammoths and living elephants belong.

Teeth suggesta diet of leavesnot grasses. Tetralophodon longirostrus

REFERENCE SECTION

LAND ANIMALS

AQUATIC ANIMALS

LAND PLANTS

WHALE DIVERSITYBy the Pliocene, modern whales hadlargely replaced more primitive forms.Sperm whales, humpbacks, killerwhales, and many modern kinds ofdolphins were all present. As Northand South America were broughttogether, the land bridge blockedmovement of marine animals from the Atlantic to the Pacific. As a result,numerous fish and other animalsunique to the Caribbean Sea evolved.

RETREATING TROPICSConditions became drier and coolerduring the Pliocene and grasslandscontinued to spread. Arid steppe andpampas environments replaced thewarmer, more wooded savannahs of theMiocene, with the result that grazinganimals flourished at the expense ofbrowsers. Tropical plants started todisappear from high latitudes andbands of cooler-adapted forests, madeup of conifers, birches, and othertrees, began to spread across northernNorth America, Europe, and Asia.Willow trees and fruiting treesfrequented the river valleys of thenorthern hemisphere. Such forestswould become even more widespreadduring the Pleistocene ice ages.

Fossilized earbone

GRASSESGrasses are among the most important groups

of plants alive today. They provide shelterand food for countless animal species.

The spread and diversification ofgrasses started in the Miocene andcontinued through the Pliocene asconditions became drier. Winds thatswept the Pliocene plains spreadgrass seeds, helping these plantsdominate the dry interiors ofcontinents as well as watersidehabitats. Because grasses grow fromthe bottom of their leaves (ratherthan the tops, as in other plants),they recover very quickly fromdamage caused by fire and grazing.

Grasses producehuge quantities ofpollen and seed.

Balaena

307

FOSSIL TIMELINE

EARTH FACTS

In the Pliocene, a land bridge formedbetween North and South America.Animals could move from onecontinent to the other, but oceancurrents were blocked, divertingwarm water northwards. Indiacontinued to push the Himalayas ever higher. The climate grew coolerand Antarctica froze over.

SMILODON The notorious saber-toothed cat,Smilodon, first appeared in the Pliocene

of North America, later spreading toSouth America. It had evolved to hunt the

horses, camels, and other large hoofedmammals that thrived during the

epoch. Using its powerful forelimbs,it probably pulled prey to the

ground before biting throughthe soft tissues at the bottom

of the animal’s throat.

Body about 4 ft (1.2 m) long

Retractableclaws, likethose of aliving cat

Powerfully built body

Short tail likethat of a modern lynx

Deep, powerfullower jaw

LIQUIDAMBARThese trees, sometimes called

sweetgum, grew to around 82 ft (25 m) in height. Distributed

worldwide, they formed animportant part of Pliocene

temperate woodlands. Thetwigs of Liquidambar hadcorky “wings” and theirfruits were collections ofwoody burrlike capsules,carried on long stems.Today, sweetgum trees areeconomically important.Their wood is used tomake furniture and pulpfor paper.

Distinctivestar-shapedfive-lobed leaf

Leaves wereshed in theautumn.

MACRONESAll the familiar kinds of living fish had

evolved by the Pliocene. Catfish, such asMacrones, belong to a group of ray-finned

fish that first arose in the Cretaceous. With along body that lacked scales, Macrones would

have grubbed in the silt at the bottom oflakes and ponds. Some modern catfish arevery similar to Macrones and have at times

been regarded as members of the same genus.

Sensitive barbelsgrew from theupper jaw.

Long, toothed skull,ideal for a diet ofinvertebrates

Macrones wereabout 20 in (50 cm) long

Liquidambareuropeanum

NORTHAMERICA

EURASIA

AFRICA INDIA

SOUTHAMERICA

ANTARCTICA

308

PLEISTOCENE EPOCH 1.81–0.01 MYA

MAMMALS AND HUMANSDuring the Pleistocene, temperaturesdropped in the northern hemisphere. Animals adapted to warmer climates, forexample lizards, snakes, and lissamphibians, were pushed southward. In their place there developed numerous large, fur-covered mammals that were better suited to the cold. Among these were newmammoths, woolly rhinos, cave lions, andgiant deer. New human species emerged inAfrica, Europe, and Asia and began to havean effect on the diversity of large animals.

HOMO SAPIENSOur own species – Homo sapiens – arosein late-Pliocene Africa. DuringPleistocene times it spread east andnorth, and eventually colonizedEurope, Asia, Australasia, and bothAmerican continents. Homo sapiens wasthe most adaptable and successful of

the several species of Homo alive in the Pleistocene. It probably had

a more complex language and culture,and a better understanding of tools than the other species, which it gradually replaced.

Cones releasewinged seeds.

Pinguinusimpennis

REFERENCE SECTION

LAND ANIMALS

LAND PLANTS

COLD WATERSMarine invertebrate life in thePleistocene was largely unchanged from the Miocene and Pliocene.However, corals and other reef animalswere affected as sea levels fell. The colder climate worldwide meant that cold-water seabirds and marine mammals– which today are found only in polarwaters – were far more widely distributed. Auks and walruses, forexample, lived as far south as Japan and southern Europe.

GRASSLANDS AND TAIGADuring the Pleistocene, grasslandsdeveloped in the chilly northernlatitudes. These supported not onlygrasses, but cold-adapted plants such asground-hugging lichens, mosses, dwarfsedges, and miniature willow and birchtrees. Taiga – a new kind of coniferousforest – colonized the area between thecold northern grasslands (steppes) andthe temperate deciduous forests farthersouth. During warm spells, grapevines,hazels, and oaks returned to the north.Tropical forests retreated, and the SouthAmerican and African rainforests mayhave been split into small “islands” bybands of grassland. Climate changes atthe end of the Pleistocene resulted inthe decline of the steppes.

PINGUINUS The Great Auk, Pinguinus impennis, was a

flightless seabird that inhabited the coolseas of the northern hemisphere during

the Pleistocene. It occurred as far south asnorth Africa and Florida. Like the living

penguins, it would have “flown” underwaterchasing after its prey of fish and crustaceans.

Pinguinus survived into the Holocene butwas mercilessly hunted by humans for its

feathers and oil. The very last GreatAuks died before 1860.

PICEA Spruces (Picea) are pine trees that formed much of thetaiga – the vast forests that spread through the northernhemisphere in the Pleistocene. Today more than thirtyspecies of spruce live in subtropical, temperate, ormountainous regions of the world. Picea trees aretypically tall and narrow with drooping branches,giving them a “layered” appearance. Theyhave rectangular needles and thin,scaly bark. Their cones arelong and are attachedby a long stalk.

AQUATIC ANIMALS

Woody cone covered withbracts in diamond pattern

309

FOSSIL TIMELINE

EARTH FACTS

Huge ice sheets covered northernNorth America, Europe, and Asia.Southern South America, Australia,New Zealand, and Antarctica werealso icier than today. Pleistocene sealevels were around 330 ft (100 m)lower than the present day, and dryland linked North America to easternAsia and Australia to New Guinea.

DIPROTODONHerds of this giant marsupial are thought to haveroamed the Australian grasslands of the Pleistocene.This rhinoceros-sized herbivore was equipped withlarge chewing teeth set into thick, heavy jaws.Diprotodon’s relatives had been around since theMiocene, but declined as Australia became drier. Theirrole was taken over by the large grazing kangaroos thatstill survive to this day.

RANUNCULUSButtercups (Ranunculus) are

flowering plants that grow ingrassland, wetland, and woodland

environments. They are among the oldestgroups of flowering plants and weresuccessful and widespread in the temperate

environments of the Pleistocene. Today,about 2,000 members of the buttercupfamily are found as herbs, shrubs, andvines. Buttercup flowers are poisonous.Their shiny coating irritates thedigestive tracts of animals that eat them.

HYDRODAMALISSteller’s sea cow (Hydrodamalis gigas) was a kelp-eating marine mammal related to themodern dugong of the tropicalIndian Ocean. It lived in the coldArctic seas, protected from theicy water by layers of fatbeneath its barklike skin.Like Pinguinus, itsurvived into theHolocene and was hunted toextinction by 1767.

Ranunculusspread acrossNorth America,Europe, andAsia in thePleistocene.

Whalelike tail flukes

Some Diprotodon skeletonshave marks indicating thatthey were hunted byprehistoric people.

Small brain

Strong, heavy,columnlike limbs

Short feet wellsuited forbearing theanimal’s weight Flippers

blunt andstumplike

Buttercups canhave yellow,white, red, orblue flowers.

AFRICA

SOUTHAMERICA AUSTRALIA

ASIANORTHAMERICA

EUROPE

ANTARCTICA

310

HOLOCENE EPOCH

DIVERSITY IN DECLINEThe Holocene has been dominated by humans. The result of their success has been a large drop in the diversityof life on Earth. The human specieshas multiplied like no other before,and has spread to the most isolatedplaces on the planet. Humans havedestroyed the habitats of otherspecies to feed and house growingpopulations. They have huntedcreatures to extinction, and createdpollution that threatens animal andplant life worldwide.

REFERENCE SECTION

AQUATIC ANIMALS

LAND ANIMALS

WATER LOSSESAs on land, the most significant aspect of life in the Holocene seas has been destruction caused by humans. Some seals and sea cows have beenhunted to extinction, and whaling carried outbetween about 1850 and 1950 almost wipedout some of the great whale species.Industrial-scale fishing has changed the balance of life in the seas, whilerivers and oceans are increasinglyused as dumps for chemicals,sewage, and solid waste.

HUMAN INFLUENCEAt the start of the Holocene, elm, birch,and conifer woodland colonized thoseparts of the northern hemisphere thathad previously been covered by ice.Vast tracts of these woodlands, as wellas wetlands and tropical forests, werelater destroyed as humans clearedand drained land for agriculture.Humans cultivated a few selectedspecies of grasses – the cerealcrops – which today dominatehuge areas at the expense ofnatural plant communities. Otherapparently natural habitats, suchas moorlands, heaths, andgrasslands, are actually createdand maintained by humanactivity, such as deliberateburning and grazing of livestock.

SALMONFound in rivers, lakes, and seas throughout the northernhemisphere, salmon have been

an important food source forpeople for thousands of years.

Today wild salmon are hunted forsport, and some species are farmed. Salmon numbers have been hit by

water pollution and by the constructionof dams, which prevent the fish frommigrating upstream to breed.

LAND PLANTS

OAK MOSSAlthough it iscalled “oak moss,”Evernia prunastri is in fact alichen – an alga and a fungusgrowing together symbiotically. This greenish-gray, bushy lichengrows throughout much of the northern hemisphere. Somescientists believe that lichens may have been the first multicellularorganisms on Earth. Today, many lichens are dying off as a resultof pollution. Some types, however, have successfully colonizedbuildings and now flourish in towns and cities.

DODO The dodo (Raphus

cucullatus) was a giantflightless pigeon that livedon the island of Mauritius

in the Indian Ocean. Dodoswere not shy of the people

that visited Mauritius in the1500s and 1600s. This made

them very easy to catch, and byabout 1680 the species was extinct.Thousands of other island-dwellingspecies suffered the same fate.

Salmon require water witha high oxygen content.

Prominent curved beakand naked facial skin

Branching, leafythallus (body)

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FOSSIL TIMELINE

EARTH FACTS

Sea levels rose in the Holocene as the Pleistocene ice retreated. Global warming caused by pollutioncontinues this trend today. By thestart of the Holocene the land bridgethat linked Asia with North Americawas under water and New Guinea wasseparated from Australia. Africa andAustralia continue to move northward.

DUCKDucks are omnivorous water birds that evolved at the end of the Cretaceous. The Mallard (Anas platyrhynchos) is a freshwater species native to Europe, Asia,and North America. It has been domesticatedand introduced worldwide. As withother domesticated birds,people have bred typesof Mallard thathave fancyplumage or growespecially fat.

GIANT PANDAGiant pandas are Asian bears specialized for eating bamboo. Three species evolved in the Pleistocene but only one, Ailuropoda

melanoleuca, survived into theHolocene. Many of the large

bamboo forests that pandasneed have been cut

down and the fewsurviving pandapopulations are now widely separated.Pandas are also slowto breed and are

hunted by poachers.

DOLLY THE SHEEPPeople have always “engineered”domestic animals by breedingfrom carefully selected

individuals. Advances ingenetics now let biologistsmanipulate the geneticmaterial of living things. Thismeans that embryos can becloned, a process thatresulted in Dolly the sheep,born in 1997. In the future,genetic engineering willincreasingly be used to modify the features of living things and evencreate new species.

BLUE WHALEThe invention of the explosive harpoon

in the late 1800s enabled humans to hunt the giant Blue Whale

(Balaenoptera musculus) to near extinction. It is still anendangered species, thoughits numbers have recoveredto about 10,000 worldwide.Blue whales are among thelargest animals ever tohave lived. They can reach

100 ft (30 m) in length andweigh more than 100 tons

(100 tonnes).

WHEATEarly in the Holocene people began to domesticate wild grasses. Theydeliberately cross-bred the types whichproduced the most seeds, or grew thefastest. Emmer is a primitive kind of

wheat (Triticum) first domesticated in the Middle East. People soon

found that by cross-breedingemmer with other kinds

of grasses they couldproduce hardier,

even moreproductive

wheats.

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0.01 MYA–PRESENT

Wheat is milled toproduce flour.

NORTHAMERICA

AFRICA

AUSTRALIASOUTHAMERICA

ASIA

ANTARCTICA

MAPS, PHOTOS, AND SATELLITE IMAGESGeological maps show the different types

or units of rock that are exposed onthe Earth’s surface. They are widely

used when searching for potentialfossil-bearing sites. Investigationsby geologists have determined theages of the rocks and theenvironments in which they were

deposited. Aerial photographs andsatellite images can be used in

conjunction with geological maps sothat the locations of exposed rocks can

be pinpointed. These tools are vital wheninvestigating remote or poorly known areas.

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FINDING FOSSILSNEW FOSSILS ARE DISCOVERED all the time, but only become known as collectors,enthusiasts, and researchers share theirknowledge and announce their discoveries.Many finds are made in areas that have beensearched for years or decades and yetcontinue to produce material as new rocksare exposed and new fossils unearthed. Manyof the world’s most prolific fossil-bearingsites, such as the Gobi Desert and theCretaceous rocks of southern England, arefamous and are regularly visited by organizedexpeditions and local collectors. Other areas,including the African deserts, remote partsof South America, and the polar regions,have only recently been discovered as richsources of fossils.

WHICH ROCKS?Most fossils are found in sedimentary rocksthat form in layers from deposits of sandand mud – those with tiny particles canpreserve fossils in incredible detail.Metamorphic rocks have been modified byheat and pressure below the Earth’s surface,so any fossils they once contained haveusually been destroyed. Igneous (volcanic)rocks rarely contain fossils, since they burnorganic material away when molten, butfossil footprints may still be preserved onthe surface of lava. Permanently frozenground, such as the permafrosts of Siberia,can also preserve organisms.

REFERENCE SECTION

Chalk (limestone)

Rock sandstone

Different colorsindicate materials thatreflect radio wavesdifferently.

Lyme Regis, England

Shale cliffsformed in theJurassic

Stripes indicate outcrops ofCretaceous sedimentary rock. Radar-bright cliff face

Satellite radar image of Egyptian desert

Sea constantlyerodes cliffs,causing rockfalls.

SEDIMENTARY ROCK TYPESSedimentary rocks are made from ground-up

fragments of other rocks, as well as material from living organisms. Clays and mudstones are made up of minuscule mud particles, while limestones contain the remains of billions of tiny organisms, cemented together by the mineral calcium carbonate.Sedimentary rocks mostly form on the seafloor, where fresh sedimentsare continuously deposited after being washed off the land. Manysedimentary rocks contain rounded lumps called concretions. These areproduced by chemical changes, often caused by the presence of a fossil.

Rock clay

Fallen rockcontainingcluster ofammonitefossils

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ONSITE ACTIVITIESPaleontologists looking for fossils may spend hours walking a site,peering at the ground or at the surfaces of exposed rocks. Ratherthan digging holes and hoping to find fossils by chance,paleontologists generally look for places where they have alreadybeen exposed by erosion. Paleontologists learn to spot fossils bylooking for shapes or textures – bones are often noticed becauseof their smooth, shiny outer surface or their honeycombedinternal fabric. Shells, teeth, and other fossils often havedistinctive shapes and surface textures.

FINDING FOSSILS

Site walking in the Gobi Desert

FINDING FOSSIL REMAINSIndividual collectors investigate cliffs, seashores,and other places and find hundreds of fossils,often of new species. Many digs are the resultof an initial small discovery made by a localcollector. They are carried out by amateursor teams of scientists, close to where thesepeople live or work. Larger-scale expeditionsoften aim to investigate specific fossilenvironments – they expect to bring backmany specimens, and may hope to discoverseveral new species. Such expeditions oftentravel to remote areas – they are expensive,involve months of planning, and may involveteams from several different countries. It mayalso be necessary to obtain special permissionfrom governments.

EXPOSURESFossils are mostly discovered where fossil-bearing rocks have beenexposed by the actions of water, wind, or people. Eroding cliffsand riverbanks are the best places to find fossils since constanterosion means that new fossils are always being exposed. Fossilseroded from cliffs and from rocks exposed at sea may be washedaround in the surf for years, and seashores may be littered withfossils. As a result, seashores are one of the best places to findfossils. Where people have exposed rocks - in quarries, road cuts,and building sites – fossils may also be exposed. Places where rocksurfaces are not covered by soil and plants, such as rocky deserts,are also important places for the discovery of fossils. To findspecific kinds of fossils, fossil hunters examine particular kinds ofrocks deposited at specific times and in specific environments.This means that knowledge of the geological history of an area isimportant for successful fossil hunting.

Rock outcrops in theGobi Desert date to theLate Cretaceous.

Fossil hunters may have towalk for miles across thedesert in search of promisingexposed fossils.

Exposed shellsin limestone

Fossil-hunting expedition in West Africa

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TECHNIQUES OF EXCAVATIONREMOVING AND TRANSPORTING A FOSSIL can takeone amateur fossil hunter a matter of minutes,or involve a whole team of paleontologistsworking painstakingly over weeks or evenmonths. Every year, major museums senddigging parties to rich fossil sites around theworld. In the field, they can face a variety ofchallenges, from delicate and crumbling rocksto huge lumps of bone that require heavylifting equipment to transport, and may evenhave to be cut into pieces on site. Majorexcavations may use cranes, helicopters,digging machines, and even explosives.

EXCAVATION IN PROGRESSNormally, the surrounding rock is not completelyremoved from a fossil until it is safely back in thelaboratory. In the field, most specimens are excavatedas part of a block that contains the whole fossil andhelps protect it during transport. Freeing a specimenfrom the rock, and removing the rock that lies on topof it – known as the overburden – can be difficult.

Some rocks are so hard thatexplosives and heavy-duty

machinery like bulldozersand power drills may be

needed. However, not allrocks are so difficult toremove – some softsandstones andmudstones can besimply washed orbrushed away from thefossils they contain.

REFERENCE SECTION

Small excavation tools

TOOLS OF EXCAVATIONExcavation tools range fromtoothbrushes and scalpels to shovels andhammers. Once the position of the fossilitself is known, heavy tools can be used toremove most of the overburden(overlying rock). Gloves, protectivegoggles, and hard hats are needed toprevent injury from flying shards of rock.As the rock layer around the fossil isreduced, smaller and more delicate toolsare used. Sieves are also used to siftthrough the overburden forsmall fossils, which may provevery useful for establishing alarger fossil’s context.

Protective gear

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MOVING FOSSILSMany fossils are fragile and prone to cracking andbreaking, so glue and resin are painted or sprayedon to help keep them together. Small fossilscollected in the field can be kept safe wrapped inpaper or stored in sample bags. Large fossils mayneed to be wrapped in plaster or have their mostfragile parts protected by polyurethane foam. Someblocks containing fossils may be so large that theyhave to be split apart for ease of transport.

Site mapping in progress

TECHNIQUES OF EXCAVATION

MAPPING THE SITERecording the precise positionsand relationships of fossilson a site can revealimportant cluesabout how anorganism died andhow it came to bepreserved. Beforeanything is removedfrom the site, it isdivided up using a grid,photographed, andaccurately mapped. Thedifferent fossils are alsoclearly labeled so there is noconfusion when they are freedfrom the rock and taken backto the laboratory. The endresult is a detailed site map thatcan be almost as important as the fossils themselves.

STABILIZINGIf the rock around afossil is crumbly or the fossil itself has been exposed to theelements, it often needs stabilizing before it can be moved.Stabilizing helps to keep a fossil block together and protect itfrom damage during transport. Stabilization methods rangefrom simply painting the exposed parts with glue or resin, towrapping the whole block with bandages of burlap cloth soakedin plaster of Paris – just like putting a broken leg in a cast.

Plaster and bandages

Paintbrushes

Stabilizing a fossil prior to removal

REMOVALFinal removal of the fossil is a delicate moment.Often rock from below the fossil block is dug out first,leaving just a stump that has to be chiseled throughor broken off. Once freed, the block can be turned

over, and its undersidestabilized. It may thenhave to be transportedfor hundreds of milesfrom remote areas by

jeep, plane, boat, oreven horse-drawn cart.

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SIBERIAThe wildernesses ofnorthern Siberia arecovered with thicklayers of permafrost,which have trappedand preserved theremains of Ice Ageanimals such asmammoths. Thisunique method ofpreservation retainssoft body parts as wellas bones andimmense tusks.

THE KAROOSouth Africa’s Karoo Basin is astorehouse of fossils from thePermian to the Jurassic, charting therise and diversification of synapsidsand reptiles. Animals from the Karooinclude Lystrosaurus, Euparkeria,Dicynodon, and Thrinaxodon.

SOLNHOFENGermany’s Solnhofen quarry wasonce a shallow tropical sea withscattered islands. The fineSolnhofen limestones havepreserved the delicate remains offish, as well as island-dwellers likeCompsognathus and the early birdArchaeopteryx (discovered in 1861).

LYME REGISThe slate cliffs of Lyme Regis insouthwest England were amongthe earliest fossil sites, wellknown by the early 1800s.They preserve animals fromthe Jurassic seas, includingichthyosaurs and plesiosaurs.

MESSELThe Messel quarry in Germany preservesthe remains of an entire ecosystem fromPaleogene times – the period whenmammals were diversifying and assertingthemselves. Fossil mammals found atMessel since its discovery in the late 19thcentury include opossums, bats, rodents,early primates, and primitive horses. Otherfinds from the site are insects, frogs,predatory fish, reptiles and crocodiles,birds, snakes, and plants.

OLDUVAI GORGEThe Olduvai Gorge in Tanzania is animportant site because it preserves some of the earliest-known human remains,alongside prehistoric mammals such asantelope, zebra, pigs, hippopotamuses, andelephants. Discovered in the early 1960s byhusband and wife paleontologists Louis andMary Leakey, early hominids from OlduvaiGorge include Australopithecus habilis,Australopithecus boisei, and Homo ergaster.

REFERENCE SECTION

Fossil bat from Messel deposits

Ichthyosaurus

FAMOUS FOSSIL SITESRICH FOSSIL BEDS ARE SCATTERED all around the world,preserving the remains of life from a variety of differentages. However, only a few very specific geologicalenvironments are able to preserve fossils well. The mostwidespread are fine-grained sedimentary rocks, but otherpreserved remains have been found trapped in Siberianice, or drowned in Californian tar pits. Paleontologistsknow that our view of the prehistoric world can never becomprehensive, because we see it through such narrowwindows into the past.

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RANCHO LA BREAThese tar pits, near LosAngeles, are a unique sitewhere Ice Age animals weretrapped in the pools ofliquid asphalt that form onthe surface. The first boneswere discovered in the 1870s,but proper excavation didnot get underway until theearly 1900s. The pits have sofar revealed more than 565species, ranging frommammals such asmammoths, saber-toothedcats, and dire wolves, toinsects, fish, and frogs.

COMO BLUFFThis vast Jurassic deposit ofmainly sauropod skeletons inWyoming was discovered in the1870s, during the building ofthe Union Pacific Railroad. Itincluded remains of giants suchas Apatosaurus, Diplodocus, andCamarasaurus. Nearby BoneCabin Quarry, excavated byAmerican Museum of NaturalHistory scientists from the1890s onward, yieldedhundreds more specimens.

VALLEY OF THE MOONThis barren valley in WesternArgentina is the source ofsome of the earliest dinosaurfossils. In among therhynchosaurs and other rulingreptiles from the Late Triassicperiod are two early theropoddinosaurs – Eoraptor andHerrerasaurus. This remote sitewas discovered in the 1950s,but its true richness was onlyrevealed in the late 1980s.

EDIACARAEdiacara, in Australia’s Flinders mountainrange, was a sea in Precambrian times,and preserves some of the earliest knownremains of complex organisms. Thecreatures found here resemble sea jellies,sponges, sea pens, annelid worms, andeven arthropods.

RIVERSLEIGHThe Riversleigh quarry inQueensland, Australia,holds the record fordensity of fossil finds.Discovered in 1900, it wasnot seriously excavateduntil 1983. The diggersfound a huge range offossils from the Neogeneperiod, includingmarsupial mammals suchas kangaroos,diprotodontids, andmarsupial lions, as well ascrocodiles, snakes, andgiant flightless birds.

THE FLAMING CLIFFSThe Flaming Cliffs of Mongolia’sGobi Desert have yielded some ofthe world’s best-known dinosaurssince their discovery in the 1920sby Roy Chapman Andrews. Thecliffs preserve fossils from the LateCretaceous, including Protoceratops,Oviraptor, and Velociraptor.

FAMOUS FOSSIL SITES

The Ediacarafossil Spriggina

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FOSSILS IN THE LABFINDING AND EXCAVATING A FOSSIL is only the first step inunderstanding it. Paleontologists actually spend far moretime in the laboratory than in the field. This is where thefossil is removed from its protective field jacket and theoften painstaking task of separating the fossil from therock around it takes place. Removing rock and cleaningand piecing fossils together may involve mechanical toolssuch as hammers and brushes, as well as chemicals. X-raytechnology can be used to reveal how muchof a fossil is preserved while it is stillencased in the rock. Once it is prepared, a fossil’s anatomy can be studiedto reveal its secrets.The results of thesestudies are publishedin scientific journals.

FREEING FOSSILS FROM ROCKOnce a fossil is in the laboratory, the protective jacketput on it in the field can be removed. As rock thatsurrounds the fossil in its block is removed, exposedelements may need strengthening with glues andprotective resins. Removing rock from all the finedetails of a fossil can be a delicate and time-consumingprocess, and jackhammers, drills, knives, files, andbrushes are used according to how much rock needsremoving. Sometimes CAT-scan images of the fossil inthe rock are used to guide the preparation process. Inthe final stages, particularly for small fossils, removalof rock particles may be performed with fine toolsunder the microscope.

CATALOGING FINDSExpeditions usually return with hundreds ofsmall fossils in addition to their major finds.These can help give context to other materialfound around them, and so are carefullycataloged. Over the years, paleontologistshave built up lists of index fossils – rapidlychanging, widespread, and common animalsthat can be identified from tiny fragments.Because the age of these fossils is preciselyknown, remains found alongside, above, orbelow them can also be dated.

REFERENCE SECTION

Hammer and chisel

Dental drill

Saw is used to cleanaway small areas ofrock.

Drill is used for themost delicate finalcleaning.

Hammer and chisel canonly be used for removinglarge chunks of rock.

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SCIENTIFIC DESCRIPTIONOnce a fossil is fully prepared, apaleontologist can begin to describe theanatomy of a fossil and compare it withmaterial from related or similar species.Unique features may show that a fossil is anew genus or species, in which case it hasto be given a new name. By comparingthe features of a new fossil with others, itcan be incorporated into a phylogeny(evolutionary sequence of events) andprovide new information on the evolutionof a group. Using what is known of livinganimals, paleontologists can reconstructmuscles and degrees of motion possible at joints. This can provide information on how fossil animals may have lookedand behaved when alive.

ACID PREPARATIONBy using acids, paleontologists canremove the rock from around a fossil,without damaging the fossil itself. Diluteacetic or formic acids are used toremove limestones, while other acids areused to break down silica- or iron-richrocks. The results of acid preparationcan be spectacular, but the process mustbe carefully monitored as acid cansometimes dissolve fossils from theinside. Some acids are dangerous andcan burn human skin, so people usingthem must wear safety masks, gloves,and clothing.

REVIEW AND PUBLICATIONOnce a fossil has been studied, its description is published as ascientific paper for the rest of the scientific community to readand refer to in later work. The paper is a technical articlepublished in a specialist journal. It may be a description of anew species, a re-evaluation of long-known species, or a study ofthe evolution, structure, or biology of a group. Diagrams andphotos are used to illustrate the features or concepts discussed

in the paper. Although mistakes happen, mostscientific papers that make it to publication

are reliable, since they have already beenpeer-reviewed. Before publication, the

paper is sent out to other experts inthe field, who can comment on itand recommend changes. Often,when a new and spectacularanimal is discovered, the mediabecome interested, the story

appears in newspapers, and thediscoverer can become famous.

ILLUSTRATIONPaleontologicalillustration andrestoration is an art initself, and the key todescribing what an ancientanimal really looked like. Illustrations can varyfrom precise drawings of the fossil still in its rock, to complete andlabelled reconstructions of the articulated skeleton, like the one shownhere. For precision, scientists often use a camera lucida – a simpledevice that projects an image of the fossil onto paper, allowing itsoutline and details to be traced. Although drawings are less accuratethan photographs, they are useful because they can combine featuresthat could never be seen at the same time in the fossil itself.

FOSSILS IN THE LAB

Cleaning a fossil in an acid bath

A new dinosaur appears on thecover of Nature.

American Museumof Natural Historypaleontologistsexcavating fossilsin Mongolia

Scientific illustrationof the Cambrianarthropod Opabinia

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STUDYING FOSSILSPALEONTOLOGISTS STUDY THE ANATOMY of fossils to reveal evidenceabout lifestyle, diet, growth, and movement. Anatomical details alsoprovide a great deal of information on the evolutionary relationshipsbetween species. A lot of paleontological work thereforeconcentrates on the accurate description of a fossil’sanatomy. Tomography – the use of X-rays to viewinternal structures three-dimensionally – andmicroscopy, the use of microscopes, have becomeincreasingly sophisticated and allow improvedinvestigation of anatomy. Paleontologists can now seeinside fossils without breaking them open and can viewdelicate internal structures never examined before.

ANATOMYThe anatomy of a fossil animal provides a wealth ofinformation, not just on the possible lifestyle andstructure of the creature it preserves, but on theevolution of the group to which it belongs. Bycomparing an animal’s bones with those of similarforms, paleontologists formulate ideas about the

evolutionary relationships between species. Softtissues like muscles and organs are rarelypreserved in fossils, but their probablestructures can be inferred by comparing theanatomy of fossil animals with living ones.

MUSCLES AND ORGANSScars, crests, and ridges on fossil bones canshow where muscles were attached in life –something that can be tested by looking atthe muscles and bones of living animals.The positions and sizes of muscles in fossilanimals, and the amount of movementpossible at bony joints are measured.These are used to reconstruct the way the

animal might have moved and what it wascapable of when alive. Internal organs

are more difficult to reconstruct,although some exceptional fossils can

preserve traces of these structures,and comparisons with living

animals can also be valuable.

SKULL AND TEETHBy looking at the evidence for eyeballs,nasal tissue, and ears, paleontologists canlearn about a fossil animal’s senses. Teethprovide an indication of lifestyle –carnivorous animals typically have sharp-edged or conical, pointed teeth, whileherbivores typically have leaf-shaped orflattened chewing teeth. The arrangementof teeth in the mouth can also provideinformation about the animal’s feedingstrategy – for instance whether a carnivorewas a predator or scavenger.

REFERENCE SECTION

Long neck forsnapping upinsects andother smallprey

Internal anatomy basedon a modern bird’s

Tail musclesreconstructedfrom ridges ontail vertebrae.

Birdlike muscular gizzard forcrushing food, based on findingsof gizzard stones associatedwith dinosaur fossils

Hip acted as a pivot point –Gallimimus’s tail balancedthe rest of its body.

Large forward-facing eyesindicatestereoscopic(3-D) vision.

Large nostrilsshow a keensense ofsmell.

Saber teethshow theanimal wasa fearsomehunter.

Saber-toothedcat skull

Shins longer than thighsare similar to those foundin ostriches, so Gallimimuswas a fast runner.

Sharp foot claws wereprobably used asdefensive weapons.

Long arms could havebeen used to collectvegetation or grab prey.

Birdlike beak indicates Gallimimusmay have had birdlikefeeding habits.

Anatomical modelof Gallimimus

Skin coveringbased on modernreptile – dinosaurskin is rarelypreserved.

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LOOKING CLOSERMicroscopy has been used to study fossils

since the earliest days of paleontology, butrecent advances have allowed scientists tolook much more closely at prehistoricevidence. Scanning electron microscopesallow far more detail to be seen in fossilbones. They have also revealed fossilizedmicroorganisms for the first time, helpingpaleontologists to learn more about theenvironment the larger animals lived in.Tomography involves the use of X-rays to lookinside an object. It has been used to look atstructures such as the complex hollow tubeswithin the skull of duck-billed dinosaurs.

PALEOPATHOLOGYThe study of ancient diseases and injuriesis called paleopathology. These can berecognized by preserved changes orpeculiar growths in bones and mayindicate that fossil animals endureddisease or injury when alive. Featuresseen regularly in many members of afossil species – such as injured horns in fossil antelopes or broken teeth incarnivores – indicate that these structureswere often used in combat or defense.

CT SCANSCT (computerized tomography) scans enablepaleontologists to look inside fossil skulls andother structures without destroying them. In

conventional X-rays, objects are compressed intoa single plane, but in CT, the X-rays are used toproduce a three-dimensional computer model

that can be manipulated within digital space.Detailed structures that can only normally be

examined when a fossil is broken open, such asthe shape of the brain or the location of nerves

and blood vessels, can be viewed in this way.

MICROSCOPYBy examining fossils with microscopes,paleontologists can study fossilmicroorganisms, like bacteria andplankton. Paleobotanists routinely use microscopes to analyse the cellsand spores of fossil plants. Scanningelectron microscopes (SEMs) arepowerful tools that can magnify theimage of an object a million times.

STUDYING FOSSILS

Swollen areaof tumorgrowth

SEM image of fossil pollen grain

CT scan of a theropod dinosaur skull

Hip joint

Point where bonefractured

Vertebral spines

Body ofvertebra

Hadrosaur backbone

Iguanodon ischium (hipbone)

Thickening of bone aroundbreak shows that dinosaursurvived the fracture.

Shaft bent forwardafter repair

IDENTIFYING FOSSIL PLANTSLarge plants often become fragmented duringfossilization. Scientists then face the problem ofmatching the separate plant parts. Frequently,individual names are given to the various parts of the fossilized plant, such as its roots and cones.Many fossilized parts of the Carboniferous club mossLepidodendron have been found. Sometimes the samepart appears fossilized in different ways, such as in animpression or a cast. Scientists combine informationon each part, drawn from a variety of fossil types, to build a picture of the complete plant.

COMMON FOSSIL PLANT PARTSMost of the plant fossils that are found were depositednear lakes and swamps. Parts such as leaves, roots,fruit, and seeds are frequently preserved in detail.Windborne spores and pollen are tough because theyare composed of a resistant organic material. Theirmicrofossils are often found in rocks with no otherevidence of life. Fragile petals are rarely fossilized.

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Lepidostrobusencased in ironstone

The fossilized cone of theclub moss Lepidodendronis called Lepidostrobus.

The fossilized root-bearingbranches, or rhizophores,of Lepidodendron arecalled Stigmaria.

PALEOBOTANY

Fossilized tree stumpof Lepidodendron

Cycad

THE STUDY OF FOSSIL PLANTS, or paleobotany, is the means by which scientists understand plantevolution. Fossilized plants are used by scientists toreconstruct prehistoric environments, and tounderstand the relationship among seed plants.Since the fossil record for plants is less completethan for animals, many questions about plantevolution are still unanswered. The oldest fossilplants are Precambrian calcareous algae, whichlived in shallow seas and built stacked “mats”known as stromatolites. Plants did not begin to spread onto the land until about 410 millionyears ago. Early land plants were no more thansimple shoots with a creeping root system. Fernsappeared in the Devonian period, while conifersand palmlike cycads appeared in the Mesozoic era.The flowering plants, which dominate the worldtoday, did not appear until the Cretaceous period.

REFERENCE SECTION

Woody plants, suchas this cycad, areeasily fossilized.

A cast of the inside of thestump and roots, createdwhen fine sediment filledthe hollow stump.

Fossilized bark of Lepidodendron

Fossil pollen grain magnifiedhundreds of times

Glossopteris coveredthe continents oncejoined as Gondwana.

FOSSIL POLLENThe specialized study of fossilizedpollen and spores is known aspalynology. Pollen grains havedistinctive shapes, so they areuseful for identifying plants.Pollen and seeds can evenprovide information on thereproductive structure ofancient plants. Fossil pollen is also vital in dating rocksfrom which no other fossilremains have been recovered.

BIOGEOGRAPHYThe mapping of plant fossils is very useful in proving themovement of continents. For example, if finds of the Permianplant Glossopteris are plotted on a modern map, its distribution ismeaningless. It is hard to understand how the same plant could be scattered over such vast distances and contrasting climates.However, if the Glossopteris finds are plotted on a reconstruction of the Permian world, they form a relatively continuous belt thatruns across the cooler latitudes found in the southern continents.

RECONSTRUCTING ANCIENT CLIMATESPlant fossils can be used as indicators of prehistoricclimates. Scientists study the density of stomata – poresthrough which gases pass in and out of plants – onfossilized leaves. The greater the density of the stomata,the lower the level of carbon dioxide in the atmosphere.Pleistocene pollen can be used to identify ice ages.During cold phases, arctic plant species predominated,while warm interglacial phases were reflected in a preponderance of subtropical species.

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PALEOBOTANY

The fossil remains of planetrees are found in LateCretaceous rocks of thenorthern hemisphere.

Distribution ofGlossopteris duringthe Permian period

Eocene daisypollen grain

Cretaceousplane tree

pollen grain

Lepidodendron grewto a height of morethan 165 ft (50 m),and had rhizophoresthat could spreadout for 40 ft (12 m).

PAST ENVIRONMENTSFrozen air bubbles trapped deep withina glacier reveal the makeup of ancientatmospheres. Similarly, the analysis ofoxygen molecules trapped in the shellsof marine organisms can indicate thetemperature of the oceans and theatmosphere when the animal was alive.The distribution of plants can provideinformation about ancient climaticconditions. When the global climate was warmer than it is today, forestscovered much of the globe and warm-habitat plants were found at higherlatitudes. Finds of certain plant fossilscan therefore give clues about theEarth’s temperature at a particular point in global history.

ANCIENT SEASFossils of marine organisms can reveal much about Earth’schanging coastlines. They alsoindicate fluctuating sea levelsduring Earth’s history. Theshallow seas of the Cretaceouscan be traced in deposits of chalk – the compressedbodies of millions of tiny algae called coccolith. Fossilscan also provide more specificinformation. The shells ofForaminifera – Pleistocenemarine protozoans – coiled tothe left when sea temperatureswere below 9°C (48°F), andcoiled to the right when seatemperatures were higher.

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SCIENTISTS USE FOSSILS to reconstructancient communities and environments.By closely examining fossil organisms andthe rocks in which they were deposited,paleoecologists can understand theenvironment in which the organismslived. Paleoecology uses knowledge of modern ecological patterns toreconstruct past lifestyles. As in themodern world, ancient environmentsconsisted of a range of habitats thatincluded valleys, deserts, swamps, forests,reefs, and lakes. Each habitat contained a range of ecological niches, and eachniche was inhabited by an animal orplant that had adapted to specificenvironmental conditions. Examinationof a collection of fossils from a certainhabitat allows scientists to reconstruct an entire ecosystem and to understandthe ways in which extinct organisms may have coexisted and survived.

Scientist with an icecore sample

Canis dirus, the direwolf, a North Americanplacental mammal

REFERENCE SECTION

Thylacinus, anAustralian marsupial

Thylacinuswalked on itstoes, just likeCanis dirus.

PALEOECOLOGY

Glacial icecontains frozen airbubbles that giveinformation onpast atmospheres.

Analysis ofCambriantrilobites showsthat the seaswere rich incarbonates and phosphates.

PROVINCIAL ECOLOGYComparison of ancient ecosystems found in similar physicalenvironments but different provinces (locations) can show howorganisms adapted to environmental conditions. Life in Australiaevolved in geographic isolation for millions of years, yet somemarsupial mammals evolved so that they resembled placentalmammals that lived in similar ecological niches on other continents.

Specialized shearingteeth called carnassialsare unique to wolvesand other carnivorans.

Trilobite XystriduraCanis dirus and Thylacinusevolved lean bodies thatenabled them to pursue prey over great distances.

RECONSTRUCTING ECOSYSTEMSPaleoecologists piece together a prehistoric landscape by interpretingthe fossils found in a particularhabitat. Occasionally, scientistsunearth a fossil site where extensiveremains of plants, vertebrates, and invertebrates enable them to reconstruct an entire ecosystem with great confidence. At a quarry in Messel, Germany, scientistsdiscovered fossils that allowed them to reconstruct an almost complete EarlyTertiary community. The Messel site yieldedfossils of more than 60 species of plant, as well as fossils for a complete succession of plant-eating insects, insect-eatingvertebrates, and carnivorous predators.

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PALEOECOLOGY

LIVING TOGETHER Fossils can preserve evidence of physicaland biological activity within a prehistoricpopulation. Fossilized trackways showwhether animals lived alone, in smallgroups, or in herds. Rare finds of dinosaur eggs and babies can indicatewhether dinosaurs nested together, and can suggest how long the young

remained in the nest. Fossilizedanimal droppings provide

information on an animal’s diet.

FROZEN IN TIMEFossils can reveal interactions

between ancient populations.Sometimes confrontations

between species may bepreserved – a predator’s teeth marks can be visible on an animal’s bones. In rare instances, fossil

organisms are found joined in mortal combat.The stomach contents of a fossilized animal mayyield an example

of the species upon which it preyed. The Cretaceous

fish Rhacolepis is often foundpreserved in the stomachs of

larger fish, such as Notelaps.

Fossils of Velociraptor andProtoceratops locked in battle

Plant-eating dinosaurs suchas Corythosaurus may havelived in herds to increasetheir protection againstcarnivorous predators.

Velociraptor aimed itsfeet at Protoceratops’sneck in an attempt to slash its throat.

Corythosaurus herd grazing

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COMPARATIVE DATINGTO FIT A FOSSIL into the wider picture ofprehistory, paleontologists must know howold it is. In most cases, they work this out by studying its relationship to surroundingrocks and other fossils. Fossils only form insedimentary strata – accumulated layers of rock formed by layers of compressedsediment. More recent strata, normally thoserelatively closer to the surface, will naturallycontain younger fossils. Some fossils can alsobe important dating tools themselves – theycan display distinctive changes in shape andstructure over comparatively short timescales.Changes in fossils found within rock stratadivide the part of the geologicaltimescale covered in this book intothree great eras, subdividedinto periods.

BIOSTRATIGRAPHYGeological changes mean that a stratigraphic “column”does not always reflect a neat chronological sequence.Fossils of established agefound in the rocks can be vitalin establishing the history andcurrent arrangement of thestrata. They can also help toestablish links between stratafrom very different localities, aprocess known as correlation.By matching and comparingrock and fossil samples fromdiverse locations, geologistshave been able to devise ageneral stratigraphic history.

STUDYING STRATAUnconformities (breaks in a layered sequence of rocks)complicate the structure of rock strata, but also giveimportant clues to geological history. An unconformityis an old, buried erosion surface between two rockmasses, such as where a period of uplift and erosiononce removed some layered rock before the build upof sediment resumed.

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A missing layer of stratashows a gap in sedimentation,perhaps caused by a fall inwater level.

Eroded outcropof igneous rock

Parallelunconformity

Disconformity – anirregular, eroded surfacebetween parallel strata

Unconformity

Limestone containingEocene Alveolina fossils

STRATIGRAPHYThe examination of rock strata, called stratigraphy, is a vitaltool for interpreting Earth’s history. The basic principle ofstratigraphy is that younger rocks are deposited on top ofolder ones – but unfortunately strata do not always lieneatly on top of each other in the order in which theyformed. Continental drift and mountain building fold,fault, and contort rock strata, sometimes turning themcompletely upside down. Changing sea levels can accelerateor halt the build up of sediments, and upwelling moltenrocks can also disrupt the sediments. Any interruption tothe steady sequence of strata is called an unconformity.

Sediments aboveunconformity indicatethat it was under water –perhaps in a riverbed.

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INDEX FOSSILSScientists subdivide the geologicaltimescale into many units: aeons, eras,periods, epochs, ages, and zones. Azone is a small unit of geological time,defined by the evolutionary history ofcertain organisms, known as indexfossils. The most useful index fossils areorganisms that evolved rapidly and spreadwidely so they define a limited time zoneover a large geographical area. Commonfossils, such as ammonites, brachiopods,and trilobites are used as index fossils.They are widely distributed and areeasily recovered from marinesediments, and they show enoughvariation over time to provide easilyrecognizable chronological markers.

MICROFOSSILS AS DATING TOOLSThe smallest of fossils can also be

used as index fossils. They areparticularly useful for datingrocks that have been recovered

from boreholes such as thoseused in oil exploration. A very

narrow rock core can yield a largenumber of useful fossils. Datingrocks and correlating finds betweenboreholes is a vital tool in findingand recovering mineral wealth fromgreat depths.

COMMON INDEX FOSSILSIndex fossils are used to date rocks on aworldwide basis. A number of distinctiveorganisms are closely associated withdifferent geological periods. Trilobites areused for dating in the Cambrian,graptolites in the Ordovician and Silurian,ammonites and belemnites in the Jurassicand Cretaceous. Microfossils becomeimportant in the Mesozoic era, and smallunicellular fossils called foraminiferans are usedin the Cenozoic. In some periods, such as theTriassic, index fossils are rare because of a lack ofmarine sediments. The history of these periods istherefore particularly hard to decipher.

COMPARATIVE DATING

Disconformity showswhere a riverbedonce ran.

Dyke of igneousrock intrudinginto older strata

Angular unconformity –rocks below tilt atdifferent angles fromthose above.

This unconformity isthe eroded surfaceof folded strata,once mountaintops.

Cretaceousbelemnite

Derbiya –Carboniferousto Permian

Ordovician graptolite

Early Jurassic ammonites

Paleocene nummulite microfossils

Fossil brachiopods

Pleuropugnoides –Carboniferous only

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THE DISCOVERY OF NATURAL RADIOACTIVITYhas revolutionized dating in geology andpaleontology. By measuring the rate at whichcertain elements in rock formations decay intoother forms, the age of the rocks can becalculated. This “chronometric” dating methodconverts the sequence of rock formations,established by stratigraphy and comparativedating, into an absolute scale measured in millionsof years. For example, it has established that theoldest-known rocks on Earth, from northwesternCanada, are about 4,000 million years old. Otherchronometric dating methods track changes in theplanet’s magnetic field, or measure traces left bythe decay of radioactive uranium. Chronometricand fossil dates are complementary – fossils are still used to measure fine divisions, whilechronometric dates provide a broad framework.

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PREPARATION AND MEASUREMENTIn order to measure the proportions of different isotopes in a sample, scientists use a machine called a mass spectrometer,which measures the relative amounts of isotopes with differentmasses. The proportion of radioactive isotopes left in themineral indicates how much time has passed since itsradioactive clock was set. Scientists measure a number ofdifferent decay processes. The decay of uranium-235 is usedfor measuring the oldest rocks because it involves a slow seriesof decays through several forms. Potassium-40’s decay intoargon is also widely used because potassium is so widespread.

Computerdisplays results.

RADIOMETRIC DATINGRadiometric dating measures the proportions ofisotopes (atoms of different atomic weight) in so-called radioactive elements. When a molten rockcools and hardens, the isotopes in its radioactiveelements decay into lighter ones at a steady rate,so their proportions slowly but steadily change.The amount of an isotope left in a sampleindicates how much time has passed since thisradioactive clock was set to zero. The decay rateof a specific isotope is measured by its half-life –the time taken for half of the parent atoms in a sample to decay. After one half-life, only 50 percent of the parent isotopes will be left.After two half-lives, 25 percent, and so on.

ISOTOPES AND RADIOACTIVITYThe central nucleus of any atom is made up of two typesof subatomic particle – protons, which govern its chemicalbehavior and determine which element it forms, andneutrons, which give it extra mass. But most elements canexist in different isotopes – atoms with the same numbersof protons but different numbers of neutrons andtherefore different weights. Radioactivity occurs when anexcess of neutrons in a parent isotope makes the atomunstable. It splits or decays into other elements, releasingradioactivity in the process.

CHRONOMETRIC DATINGParent isotopecontains more protonsthan neutrons.

Decay transformsneutron into proton,releasing radioactivity.

Daughter isotopecontains equal numbersof protons and neutrons.

Decay of carbon-14 tonitrogen-12

Proton

Neutron

Preparing a sample for radiometric dating

Measuring isotopes witha mass spectrometer

Sample injectedin liquid form

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PALEOMAGNETISMThe Earth’s magnetic field has reversed at irregularintervals throughout its history – magnetic Northperiodically becomes magnetic South. Magneticminerals in rocks become aligned with the Earth’s

magnetic field and become fixed in that magneticorientation when the rock is formed. By

studying the volcanic rocks steadilyproduced over millions of years at the

spreading centers of Earth’s oceanfloors, scientists have built up acomplete record of Earth’s magneticreversals. Rock samples fromelsewhere – for example volcanic flowswith fossil footprints in them – can bematched with this overall record ofEarth’s magnetism to determine wherethey fit into the sequence.

RADIOCARBON DATINGOne of the most successful radiometric dating methods is basedon the decay of the radioactive isotope carbon-14 (C-14). Thisisotope is constantly absorbed from the atmosphere by livingthings, and a fixed proportion of the carbon in any livingorganism will be radioactive. But when a creature dies, it no longerabsorbs carbon, and the C-14 within it starts to decay. Radiocarbondating is used to provide accurate dates for organic materials, suchas shells, bones, and charcoal. However, because C-14 decaysrelatively quickly (its half-life is 5,730 years), it cannot datematerial more than around 70,000 years old – there is simply notenough C-14 left in older organisms. The method is very accurateand has revolutionized studies of early humans. It can be used, forexample, to date isolated sites – such as abandoned campfires –where no other remains have been found.

FISSION-TRACK DATINGThis dating method measuresthe spontaneous fission(breaking apart) of theradioactive isotope uranium-

238 within minerals such aszircon. In this unique type

of radioactive decay, thenucleus of a single

parent uraniumatom splits into twofragments of similarmass with such forcethat a trail of crystaldamage, known as afission track, is made in the mineral. The numberof tracks present increases over time, at a ratedependent on the mineral’s overall uraniumcontent. A microscope is used to measure the number of fission tracks and theuranium content of a mineral, and the age of therock is calculated from these measurements.

CHRONOMETRIC DATING

Mid-ocean ridgesshow where newbasaltic rock formsas the seafloorspreads apart.

Satellite map ofmid-ocean floor

Zircon crystal

Close-up of fission tracks

Ridges fartherfrom the centerwere formedfurther back in time.

Basaltic rock preservesthe direction and strengthof the Earth’s magnetismas it solidifies.

Sample of material isscraped off, powdered, anddissolved into liquid formfor mass spectrometry.

Reindeer bone from ancienthuman settlement

THE DETECTIVE WORK REQUIRED to put a fossilanimal back together can be very complex.Usually, only the hard parts of an organismbecome fossilized, and often only smallfragments of these are found. Paleontologistshave to identify the fossil from remains suchas shells, teeth, or bones. They usually assumethat the missing pieces, with few exceptions,will resemble those of the animal’s closestrelatives, and use these as a guide for makingreplacement parts. Once a complete skeletonhas been assembled, scientists can reconstructthe size, shape, and posture of the livingcreature. By examining fossil remains ofplants and other organisms, they can evenreconstruct the entire ecosystem where the animal once lived. Nevertheless,reconstructions are only models,representing our current state ofknowledge – our picture of extinctlife forms changes with each new find, and many fossilreconstructions undergosubstantial revisions.

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RECONSTRUCTING FOSSILS

MAKING A REPRODUCTIONMost excavated fossils are toodelicate or too cumbersome to put back together and display in a museum. Many fossils are also only impressions rather than exactreplicas of the original structure thatformed them, and so could not berebuilt anyway. For reconstruction of a skeleton, replica bones areusually cast in materials that arelight, strong, and durable. The first step in reproducing a fossil is to make a mold from the original,which can then be used to castreplicas. When parts of a fossilanimal are missing, skilled sculptorsrecreate bones based on the animal’srelatives, and the mold is then madefrom these clay sculptures.

MAKING THE MOLDThere are manytechniques for copyingfossils. Generally, a moldis made by painting theoutside with layers oflatex or silicone rubber,which sets into a solidbut flexible mirror-imageof the original. This canthen be peeled away to reveal an impressionof the original fossil.

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Latex coating painted ontofossil Barosaurus pelvis

CASTINGThe mold is now filled witha modeling material, suchas fiberglass-reinforcedplastic, or plaster of Paris.This hardens as it dries. If the fossil in question is already an impression,the molding substance can be poured directly into it. When the fossil is more fragile than thesurrounding rock, acid isused to dissolve the fossiland create a rock mold.

Liquid resinpoured into moldforms a cast.

Hollow moldpeeled awayfrom bone

REMOVING THE MOLDThe mold is now gentlyseparated from the cast. Anyrough edges on the replicafossil are carefully filed away,and the replica is painted sothat it resembles the originalfossil. In some cases, casts ofsculpted replacement bonesare deliberately coloreddifferently in order to highlight them.

Mold is removed fromcast for finishing.

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FINAL ASSEMBLYFrequently fossil reproductions are made in special laboratories, and have to beshipped, piece by piece, to museums for display. Using photographs anddetailed plans as a guide, museumtechnicians first arrange the piecesin the correct position on thedisplay floor. The model is then assembled from the base upward. As the parts are mounted, the steelframework is weldedtogether to ensure thatthe reproduction is stable.

MAKING THE FRAMEWORKSteel supports for bones of a

reproduction are designed by astructural engineer. They must

be as light and slender aspossible, yet carry the

finished model’s weightwhen it is mounted into a

realistic posture. Theframework is prepared

by blacksmiths andmetalworkers, and

each bone cast is cutand drilled so steel

tubes can runthrough the center.

Long steeltubes linkneckvertebrae.

AMNH Barosaurus display

Barosaurus’s centerof mass is very farback over its hips –evidence that it mayhave reared.

Steel joiststhrough legbones support

weight.

CONNECTING THE PIECESOnce the bones of an animal have beenreplicated, they are laid out in relation to each other. A mount maker then reconstructsthe animal’s posture based on availableevidence such as fossil footprints andcomputer models of how the animal mayhave moved. Sometimes, reconstructionscan put forward new and controversialideas – for example, the huge Barosaurusat the American Museum of NaturalHistory (AMNH) in New York ismounted rearing on its hind legs.Paleontologists are still arguing aboutwhether Barosaurus could really have

done this, but the reconstructionspeaks volumes about the way

our view of dinosaurs haschanged since the 1970s.

Predatory Allosaurus –several dinosaurs 0are often displayedtogether in a scene.

Baby Barosaurus hidesbehind its mother.

RECONSTRUCTING FOSSILS

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FLESHING OUT THE BONES of a fossil animal to restore its appearance when alive is apainstaking scientific process. Paleontologistshave to combine information from other,comparable finds with a detailed knowledgeof the anatomy of modern animals. Theycomb their excavation sites for extra clues,which can reveal the terrain in which theanimal lived, the food it ate, and itsinteraction with other animals. Despite thiscareful detective work, some of the choicesmade when restoring extinct animals aresimply a matter of educated guesswork – skintexture and color, for example, can rarely be confirmed by fossil finds. The history

of paleontology has been one ofcontinual revision – as more

information is gathered aboutextinct life-forms, restorationsare updated and, in some cases,

radically reinterpreted.

RESTORINGA FOSSILMost restorationsare based onfossilized bones,since soft parts arerarely preserved. Bonescan give an expert detailedinformation about the creature’s anatomy, size, andstance, while muscle attachment points can alsoindicate the design of the musculature. A detaileddrawing or model of an accurately reconstructedskeleton is the starting point for any full-scalerestoration. Using this as a framework, specializedartists and sculptors can, in consultation withpaleontologists, reconstruct the layers of muscleand flesh that overlaid it in life.

EARLY ATTEMPTSThe first dinosaur restorations to gain public attention were thelife-sized models exhibited at London’s Crystal Palace in 1854.Designed by paleontologist Richard Owen, they showeddinosaurs as lumbering, elephantlike creatures walking on fourlegs. This view was overtaken in the early 20th century by thework of artists and illustrators. They used their skills asdraftsmen, and their understanding of wild animals, to creatememorable illustrations of extinct animals, placed within thecontext of fully-imagined prehistoric landscapes. Among thepioneers of this new type of dinosaur restoration were ErwinChristman and Charles Knight, who worked at the AmericanMuseum of Natural History.

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Megalosaurus jaw

Megalosaurusrestoration

RESTORING FOSSIL ANIMALS

RESEARCH Reconstruction is based on thebest available research about theanimal and its relatives. Fossiltrackways reveal informationabout stance and movement.Fossilized stomach contents,teeth, and claws can alsoprovide useful informationabout diet and lifestyle. Skinimpressions are rare, but thefew finds indicate thatdinosaurs were covered withnon-overlapping scales. Skincolor is a matter of guesswork,based on our understanding of howcamouflage and display coloring worksin living animals. Fossilized

dinosaur skin

COMPUTER MODELINGIn recent years, paleontologists, artists, and filmmakers havebegun to use computers to reconstruct prehistoric animals.In the laboratory, reconstructions of skeletal joints andmusculature can show the range of movements possible foran animal, helping to reveal its possible lifestyle. In print, 3-Dmodeling can give images a new level of realism, while onfilm, computer generated imaging (CGi) has allowed thecreation of images that were previously impossible. Theseadvances are now widely used for both entertainment (theJurassic Park movies), and education (the Walking withDinosaurs documentaries).

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RESTORING FOSSIL ANIMALS

MAKING A MODELLifelike models can be built to any scale. Theyfrequently form part of displays in museums andexhibitions, and can be designed to reveal details ofthe animal’s internal anatomy. Models can also beequipped with sophisticated electronics and pneumaticmachinery, enabling them to move their limbs andheads, and even to roar. A reconstruction begins withan accurate scale drawing, and the dinosaur’s anatomy

is built up layer by layer arounda simple framework.Details of internal andexternal features aresculpted, and the finishedclay model is used tomake a mold. This canthen be used to createone or more resin casts.

Painted and finished cast

Rubber mould

Preliminary sketch

Wire and woodarmature

Finished clay model

ROUGH OUTLINEAn accurate scale drawing of the creatureincludes detailed muscles and internalorgans based on those of living animals.The next step is the construction of a fullyarticulated cardboard “skeleton,” which isused as a rough guide for modelconstruction. An armature of wire andwood is based on this skeleton, and formsthe body framework, which is then bulkedout with modeling clay, fabric, and plaster.

MOLDING AND CASTINGOnce the basic shape has been builtonto the armature in modeling clay,details of skin texture are workedinto the clay surface. A rubber moldis made from the clay sculpture. Acast, made of a special mixture ofmineral and polyester resin, is madefrom the mold. The final stage ofpreparation is the hand-paintingand airbrushing of the model.

FOSSIL HUNTING can be a rewarding pastime –where it is allowed. In some countries,collecting fossils is illegal on public, andsometimes even on private, land. Elsewhere,fossil hunters are allowed to collect and keepthe fossils they find. Before hunting for fossils,you must find out which rules apply in the areayou will be searching. The following 10 pagesprovide all the information an amateurcollector needs to get started. The first twopages explain how to find suitable sites to lookfor fossils, what to wear and take on a fossilhunt, and safe practices to follow in the field.The next two pages describe how to collectfossils, and how to prepare finds for storageand display. The six pages that complete the

fossil hunter section provide a mini fossilidentification key for vertebrates,

invertebrates, and plants.

RESEARCH AND REFERENCEFossils are not found in every rock, so before a fossil hunt can begin it is vital to research, not just the fossil-collecting rules of that area, but the geology of the area. Maps, guides, and other fossil hunters are all useful sources ofinformation. Many fossil sites are listed anddescribed in geological guidebooks, at regionalmuseums, and at tourist information centers.Famous fossil sites, or those that are known toyield scientifically valuable specimens, are usuallyprotected, and collecting fossils at these places is strictly prohibited. When out on a field trip, a field guide is useful to help you identify and understand the fossils you might see.

MAP MATTERSA geological map shows thepattern of rock formations in different areas. Each band of color on this type of maprepresents a different geologicalunit – rock of a certain age –and shows what type of rock is at the surface. Units may be named after the site wherethey were first described. Fossilsusually occur in sedimentaryrock, such as chalk, limestone, and sandstone. A regular mapprinted on top of the geologicalmap helps the user establish a unit’s location.

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FOSSIL HUNTERA field guide containspictures of many fossils,to help the collectoridentify finds.

Upper chalk

Clay

Lower chalk A plastic sieve is used to sift finesand and dirt, andleave larger items.

Key to geological units

Geological map

This geological mapshows the site of the local village.

FOSSILSFOS

SILSFOS

SILSFOSSILS

WHAT TO WEARMost fossils are found in rough, rocky terrain, so fossilhunters should wear sturdy boots for walking. It is wiseto check weather forecasts before setting off, and towear clothing that is suitable for the climate. In coldor wet weather, collectors should take sufficient warmand waterproof clothing. If it is going to be sunny, a long-sleeved shirt and high-protection sun creamwill provide added protection. Field equipment can be carried in a knapsack, along with adequatesupplies of food and water. Most importantly, thecareful collector should take a small first-aid kit, in case of cuts or grazes.

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SAFE PRACTICESBefore starting a fossil hunt, collectors should ensure thatthey will not trespass and should obtain permission to visit a site, if necessary. Children should always be accompaniedby an adult. There is a danger of rock fall at cliff faces, socollectors should stay away from overhangs. When huntingat coastal sites, collectors should be aware of incomingtides, which can be dangerous. It is vital to check safetyguidelines at quarries before venturing on-site.

EQUIPMENTTools can only be used at sites where fossilcollecting is permitted. They should be kept to a minimum to reduce weight. Whenworking in soft sediment – such as sand or clay– a trowel can be used to clear the area aroundthe fossil. Sieves are used for separating fossilseasily from sand and gravel. Newspaper orplastic bags can be used to protect fossil finds.A notebook, pen, magnifying glass, andcamera will help the collector to examine,identify, and record finds.

A paintbrush is used to gentlyremove dust anddirt from finds.

FOSSIL HUNTER

Long, waterproofjacket for

protection during wet

weather.

Protective suncream is appliedto the skin insunny weather.

Tough pantsor jeans are

practical.

A woolly hatkeeps the

head warm.

Sturdy boots

Thick socks make boots more comfortable.

A notebook andpencil are usefulfor recording notesand sketches offinds in the field.

Adult supervising child collector

Tape measurefor measuringthe size of finds.

Compass

Camera fortaking picturesof a locationor find.

magnifying glass

Summer clothes Winter clothes

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HIDDEN TREASURE

OUT AND ABOUTHunting is easiest in placeswhere rocks have becomeexposed to reveal their fossil wealth, such asbeaches, road cuttings,quarries, and the banks of streams that cut intorock. Fossils found loose on the seashore are usuallyheavier than shells and are of a uniform color –generally dark gray or white. Fossils found inlandare often embedded withina lump of rock called anodule, which can be gentlyeased out of surroundingrocks. It is important thatrecords are kept of exactlywhere and in what kind ofrock each fossil was found.Finds should be wrapped inpaper towels or newspaperfor protection.

Sieving can be done with an ordinary fine-mesh garden sieve.

ONCE THE AMATEUR FOSSIL HUNTER has identified a likely fossil site, the process of scanning thelandscape for fossils can begin. If the amateurhunter is allowed to take samples away, findsshould be carefully wrapped and takenhome, where the next part of the fossil-hunting adventure takes place. Thefirst task is to carefully clean fossilfinds and to strengthen any fragilespecimens. Then, fossils should be identified by comparing finds with illustrations and detaileddescriptions, which can befound in many specialist books.Once identified, the specimensshould be labeled and catalogedin a card index on whichinformation about individualspecimens can be recorded. Fossils canbe stored in special collection cabinets or in plastic boxes and cardboard trays.

An ammonite fossil can clearly be seen embedded in seashore rocks.

SIFT AND SORTA sieve is an effective way to carefullyseparate fossils from sand and gravel. It is often the best way to find fossils ona riverbank. Sieves with either plastic orwire mesh screens can be used. Two orthree shovelfuls of sand should be dugup and tipped into the sieve. Using a

gentle circular motion, the sandshould be gradually allowed to

run through the sieve, leavinglarge fragments of rock and

fossil, which can beeasily sorted out.

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FOSSIL HUNTER

IDENTIFICATION AND STORAGENotes taken in the field are useful when identifying fossilfinds. These notes can be checked against information inreference books to confirm a fossil’s identity. Fossils shouldbe stored in a cool, dry place. Specially designed woodendisplay cabinets can be used, but most collectors opt forsimpler storage arrangements, such as cardboard boxes, jamjars, and matchboxes. Each find should be carefully labeled.A good method is to give the fossil a number that refers to its record in a catalog or card index. Records should hold as much information about the fossil as possible, including its name, where it was found, and the date of its collection.

A CLOSER LOOKFossils are often very small, so it may be difficult to seefine detail with the nakedeye. A magnifying glass is

useful for examiningfinds up close.

The most usefulmagnification is x8 or x10. In someplaces, such asnational parks,fossils cannot bepicked up. Whenthe handling offossils is allowed, the magnifying glassshould be held 2 in (5 cm) from the eye,

with the fossil held thesame distance from the glass.

MAKING A MODELSometimes a fossil takes the form of an imprint in the rock. It is then possibleto make a plaster of Parismodel, using the fossil as a mold, to see what thecreature looked like. First,the fossil should be cleanedand the surface brushed withpetroleum jelly to prevent

the plaster fromadhering. Plaster ofParis should be mixedand spooned onto the fossil, ensuring allindentations are filled.The mold should beleft to set. Then thecast can be pryed away

from the fossil toreveal the replica.

CLEANING AND MENDINGIt is best to practice cleaningtechniques on unimportantfossils. Brushes can be used toremove any dirt that surroundsa fossil. Vinegar, a weak acid,will remove rock from chalkyspecimens. Forceps or tweezerscan be used when handling tinyspecimens. Fragile fossils canbe strengthened with a coatingof a 10 percent solution ofwater-soluble glue in water witha drop or two of detergent. If a sample is retrieved in pieces,it can be glued together usingan acetone-soluble glue.

Plaster castof the fossil

Fossil

Fossil is protectedin cotton balls in a shallowdisplay box.

Spoon plasterinto the fossil,ensuring allcracks are filled.

Brightly colored string tied to the magnifyingglass makes it easy to find if dropped in the field.

A toothbrush or paintbrushshould be usedcarefully toremove dust.

CORAL

The most numerousorganisms of the EarlyPaleozoic, trilobite fossilsare common in Cambrian,Ordovician, and Silurianrocks worldwide. Theirremains can be found in all types of sedimentaryrock. They ranged fromseveral inches to about 35 in (90 cm) in length.Many fossil finds areexoskeletons discardedduring molting, not fossilsof the animals themselves.

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Coral are marineanimals with a skeleton of calciumcarbonate, saclike body(polyp), mouth,and tentacles.Many coralspecies live inbranching coloniesand form large,moundlike coral reefs in tropical oceans. Othercoral forms remain relativelysolitary and are often foundfossilized in shale, whichindicates that they preferred the muddy ocean bed. Coral areamong the most common fossilson Earth. They are abundant inPaleozoic limestone and shale.Fossilized coral can be hornlike,tubelike, or treelike. The size of a colony varies from less than0.3 in (1 cm) to several feet.

Ammonites are extinct invertebrates whosechambered shells were straight or coiled.

Some shells had wavy sutures (joins).Ammonites were abundant and

diverse in Mesozoic seas, but they suffered a marked decline in diversity in the Late Cretaceousand became extinct by the end

of the Cretaceous. Ammoniteswere creatures of open tropicalseas and their fossils are foundin great numbers in limestonefrom tropical reefs. Their fossils are also found in shale

from lagoons and deeper water.The smallest ammonites were

only about 0.1 in (3 mm) inwidth, although coiled

ammonites over10 ft (3 m)

in diameterhave beenfound.

Bryozoans live in coloniesthat are made up ofthousands of individualorganisms. Most colonies areabout 1.2 in (3 cm) across,but they may reach widths of 24 in (60 cm). Branching,twiglike bryozoans are found in limestone and may be preserved in surfacesthat have weathered away.

BRYOZOANS

AMMONITES

INVERTEBRATESTHE MOST ABUNDANT FOSSILS are of invertebrateanimals. Invertebrates lived in high concentrationsand frequently in conditions where fossilizationwas likely to occur, such as shallow seas and reefs.Hard invertebrate shells are able to withstand therigors of fossilization. Arthropods and molluscs are well-represented in the fossil record, whilemore delicate, land-dwelling creatures are not very well preserved.

TRILOBITES

Alternate longand short ribs

Female shellis largerthan its malecounterpart

Elrathia

Mantelliceras

Schizoretepora

These tiny

fossils are best

seen with ahand lens.

Trachyphyllia

External wall of thissolitary coral

Bivalves include oysters, clams, and mussels.The bodies of bivalves are held within twosymmetrical, chalky shells (valves) that arejoined by an elastic ligament. Shells may growto over 12 in (30 cm) in diameter. Bivalves aremost abundant in shallow marine waters, wherethey burrow in soft sediment. Fossil molds of shells are frequent finds, as many shellsdissolved after being encased in rock. Singleshells are also common, since shells oftenseparated after the creature’s death.

Gastropods are successful molluscs that use a flattened foot forcrawling. They have a head witheyes and a mouth, and carry their

viscera (abdominal organs)coiled in a spiral shell.Evolutionary changes can

be traced in the shape of the shell. The mostancient gastropod

shells show no coiling.Eventually, shells began

to coil on a single plane.Later forms had complex,

three-dimensional coils that twist and spiral. Marine

gastropods live mainly in shallowwaters, though some have beenfound at depths of over 3 miles

(5 km). Gastropod fossils are usuallypreserved in certain limestone, either

intact or as empty molds. They range in size from 0.7 to 4.7 in (2 to 12 cm).

The brachiopod body is surrounded by two shells (valves) joined by a hinge. Fossils can befound attached to the seafloor, in muddy shale, andin mudstone. Brachiopodshells are often found injoined pairs, since shellstend to stay closed afterthe animal’s death. Fossilshells average 0.7 to 3 in (2 to 7 cm) in length.

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Crinoids, or sea lilies, consist of a cup, a number offeather arms that catchfood, and a longstem that anchorsthem to the seafloor or driftwood.Crinoids were so abundant inPaleozoic seas thattheir calcite stemsformed vast massesof limestone. Thetypical diameter of acrinoid cup was 1 in (2.5 cm), and whole specimensaverage about 6 in (15 cm) inlength. The best specimens are found in limestone, such as the Silurian rocks ofEngland and the Mississippian rocks of the US. A complete fossil crinoid is rarely found, as the bodyseparates when the animal dies. Crinoid stems, withtheir button-shaped discs, are often found under logs.

Echinoids, or sea urchins,have rigid calcite skeletonscovered by spines fordefense. Their geologicalrecord stretches back tothe Ordovician, but it wasnot until the Mesozoic thatthey proliferated. They areabundant in Jurassic andCretaceous rocks. Isolatedspines are common finds.

BRACHIOPODS CRINOIDS

Belemnites had an internal, chambered shell that was enclosed by soft, muscular tissue. Their strong,cylindrical guards preserved well, and are abundant in Mesozoic marine rock. Fossilized guards vary in length from 0.3 in (1 cm) to specimens tens of inches in length. These guards are a fraction of the size of the living animal, whose body and long tentacles extended beyond the guard.

BELEMNITES

ECHINOIDS

BIVALVESGASTROPODS

Branchingarms

The spiral whorlsof the shell areencircled byridges, or keels.

Concentricridges

Platystrophia shell

Crassatella shell

Ecphora shell

Hemiaster

Belemnitellaguard

Guardmade ofcalciumcarbonate

Cyathocrinites

Cup

Cartilaginous fish have a skeleton thatconsists of tiny prisms made of calciumcompounds. Living examples includesharks, skates, and rays. Cartilage isnot usually preserved, but teeth anddorsal-fin spines are common fossils.

Single, bladed shark’s teeth and themollusc-crushing teeth of bottom-

dwelling rays are common findsin Mesozoic and younger

rocks. Cartilaginous fishrange from 5 ft (1.5 m)

to 43 ft (13 m) in length.

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VERTEBRATESTHE EARLIEST FOSSILS of vertebrates are tiny “scale bones” that belonged to jawless fish and are found in Late Cambrian rocks.Despite their long evolutionary history and great abundance, complete fish fossils are rather rare – sea water, currents, andswirling sediment break up and disperse fossilremains. Although higher vertebrates, such as reptiles and mammals, live in a wide rangeof environments, their fossil remains are alsouncommon. The best sites for preservationare in shallow marine rocks, along old riverchannels, and in caves. The most commonvertebrate parts to be fossilized are teeth,which are made of durable enamel.

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ARMORED FISH

The oldest fossil fish lackjaws – the mouth is simplyan opening – and they are covered by thick platesand scales. They had heavyhead skeletons, but theircartilaginous internalskeletons were lighter. Early species lived in the sea,but by the Silurian, jawlessfish had moved into freshand brackish (somewhatsalty) water. These heavilyarmored fish make robustfossils. Headshields are well-represented in the fossilrecord, and are particularlycommon in red rocks fromthe Silurian and Devonian.

Fish that belong to this class are characterized by a bonyinternal skeleton. The majority of living fish are part

of this group, although they do not share commonancestors. The complex classification of bony fishis based on fin structure. Ray-finned fish havefins supported by bony rods, while lobe-finnedfish have fleshy fins, supported by a single boneat the base. This group includes the coelacanth,

the most famous “living fossil.” Ray-finned fish are very diverse and abundant, yet they have left

comparatively few remains, as water breaks up anddisperses fish skeletons. Fish fossils can be found in shale,

especially in marine black shale or in shale deposited in lakes.

JAWLESS FISH

Armored fish, orplacoderms, first appearedin the Devonian and arenow extinct. They weredistinguished by theirprimitive jaws, which were armed with slicingplates. They also hadheavily armored headshields and trunks. Smallscales protected the rest of the body and the tail.Armored fish lived on the seabed in marine and fresh water. Althoughtheir average length was no more than 5.5–16 in(14–40 cm), some speciesgrew to a great size –Dunkleosteus was more than 10 ft (3 m) long.

Upper tooth of the shark Hemipristis

BONY FISH

CARTILAGINOUS FISH

Triangular tooth hasserrated cutting edge.

A series of immovable bony plates formed an effective defense.Head shield of Pteraspis

Bothriolepisbody shield

Overlappingbony plates

Priscacaraskeleton

Mammals are animals that suckle their young. Early mammals were present in the Triassic period. During the Cenozoic era, mammals have becomethe dominant group, and have colonized mostof the Earth’s surface. Teeth make up mostmammal fossil remains. Their variety reflectsthe specialized nature of mammal teeth, which have evolved to carry out differentactivities. Repositories for fossil teeth include the sediment that fills caves and fissures in limestone. Otherfossil finds include jaw bones and other skeletal parts,

and horns. Hair israrely fossilized.

The Diapsida evolvedduring the Carboniferous,and achieved maximumdiversity during theMesozoic era, when diapsidreptiles, such as dinosaurs,marine reptiles, andpterosaurs, dominated lifeon Earth. Fossils are foundworldwide, and includeskeleton parts, teeth, and body armor.

Reptiles are traditionally grouped according to the number of skull openings behind the eye socket. Turtles and otherswith no openings are known as anapsids (“without arches”).The earliest reptiles were anapsid forms. Appearing by 300million years ago, the first kinds were small, lizardlikecreatures derived from a tetrapod ancestor. Anapsids adaptedto many environments, but fossil finds are rather rare.Terrestrial surfaces are not conducive to preservation, andfossils frequently became scattered and fragmented.

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DIAPSID REPTILESAMPHIBIANS ANAPSID REPTILES

MAMMALS

The diapsid reptiles called birds evolved fromone of the carnivorousdinosaur families. Theearliest bird remains come from Jurassic rocks.More modern birds quicklydiversified at the end ofthe Cretaceous, whenmany other reptilesbecame extinct. Fossilizedbirds are very rare becausethe evolution of flight led to generally light and fragile skeletons.

BIRDS

Scutes of crocodileGoniopholis

Frog fossil

The Carboniferous ispopularly known as the“age of the amphibians,”since the group achieved an unequalled dominancein the vertebrate world at that time. Mostamphibian fossils are of wholly or partiallyaquatic amphibians, and are found in rocksformed from Carboniferouscoal swamps. Fossils of land-dwelling Paleozoicamphibians are recognizedby their distinctive teethand flattened skulls.

Shell of turtle Trionyx

Highlytexturedsurface

Hesperornis vertebra

Lower jaw of bear

The jaw and teeth ofthis bear are well-adapted for crushingand chewing.

Club mosses date from the Late Silurian. ManyCarboniferous trees wereclub mosses, and theirtrunks were important in coal formation. Clubmosses have long, narrowleaves, and produce sporesfrom their cones. Theirextensive root systems were often fossilized.

The fossil record of ferns extends back to the Mid Devonian, and they thrived during the Carboniferous. Ferns were found

in a wide range of environments – from tropical forests totemperate zones – but they required a humid environment

for reproduction. Ferns are characterized by delicatefronds, or leaves. They reproduced by means of minutespores, which formed in clusters on the underside

of the fronds. Although many ferns were small, theyoccasionally grew to the size of trees, extending toheights of 13–16 ft (4–5 m). Tree ferns broke apartafter fossilization, and today are only represented by fragmentary fossils of fronds and trunks.

Horsetails were oncewidespread and varied, andeven included trees thatreached up to 66 ft (20 m)in height. Fossils of thesejointed plants, with theirfeatherlike appearance, are easy to recognize.Horsetails thrived in theCarboniferous and arefrequently found in thesoft, dark shale associatedwith coal seams. They arealso found in freshwatersediment from the Jurassicand the Cretaceous.

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PLANTSLAND PLANTS BEGAN TO EVOLVE in the Silurian, initially in bogs, rivers,and lakes. By the end of the Devonian, plants occupied almost everyterrestrial habitat. Plant fossils are very common in Carboniferous and Cenozoic rocks. Much of the coal (rock formed from fossilplants) that is mined comes from Carboniferous rocks, and plantfossils are usually found in coal beds. Plant fossils are commonlyfound in rocks that were once part of freshwater lakes or river deltas,and in the fossilized remains of peat. The chance of fossilization ismuch better in low-lying, swampy areas, and in temperate climates.Plant fossils are usually separated into seeds, leaves, and stems – findsof complete plants are extremely rare. Many plants are preserved as three-dimensional casts or as carbonized impressions.

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FERNS

HORSETAILS

Algae vary from unicellular to multicellular plants,

but fossil finds are rare. A few algae,

which date back to the Cambrian,had hard, chalkyskeletons. Theywere abundantenough to formsmall underwatergardens and wereoften part ofreefs. Theirremains are an

important part of much of the

limestone found in northern latitudes.

ALGAE

The earliest land plants,found in Silurian andDevonian rocks, weresimple stalks that emergedfrom ground-huggingstems. Spore-bearingcapsules appeared alongthe sides or at the tips ofupright, spiked branches.These early plants vary in size from no more than3 in (7.5 cm) to about 3 ft 3 in (1 m) tall. Thebest fossil remains of theseearly land plants occur asdark markings on shale.

CLUB MOSSES

Asterophyllites

Lepidodendronbark

Leaf bases were preserved in this silicifiedfossil – silica became incorporated into the decaying wood as it fossilized.

EARLY LAND PLANTS

Carbonizedbranches attachedto jointed stems.

Section of Osmunda stem

Hexagonal,honeycomb pattern Mudstone cast

of Mastopora

Spore capsule

Zosterophyllum

The fossilized trunks of thebennettitaleans – an extinctMesozoic group of cycad-like plants – are amongthe most spectacularfossils. Bennettitaleans aredistinguished by theirpalmlike leaves and star-shaped flowers. Some of the trees of these tropicalplants reached heights of about 10 ft (3 m).

This extinct group ofplants shared a commonancestor with ferns. Theybore true seeds, whichhung from the undersideof fronds, and could be several inches long. Fossilized seeds are common in LatePaleozoic rocks, but are rarely found attachedto plants. Most seed fernswere bushy shrubs, butsome were climbers ortrees, and could reachheights of 26 ft (8 m).

The palmlike cycads grew in the forests of theMesozoic era. They weredistinguished by leaflessstems that were crowned by a mass of stiff, largeleaves. A cycad plantreproduced by means of a large, seed-bearing cob,which emerged from thecrown of the tree. Fossilfinds of cycads are likely to come from Triassic,Jurassic, and Cretaceousrocks. Living cycad speciescan still be found.

Fossils of angiosperms(flowering plants) are

common in Tertiary rocks, although some fossils date from the Cretaceous.Fossilization preservedleaves, seeds, wood,and even pollen.Delicate plant

remains were bestpreserved in deposits

laid down in lakes andriverbeds, such as shale.

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ANGIOSPERMS

SEED FERNSCYCADS

Amber is the hardened, resinoussap of a tree. This sap wasusually produced by conifers,although some angiospermsalso exuded amber-producingsap. Most amber is less than 70 million years old, althoughsome types may be more than 100 million years old. In many cultures, amber is valued as a precious stone. Amber is also vitallyimportant because it acts as a fossil trap. Smallinsects and animals thatbecame embedded in thesap while it was still viscouswere preserved in exquisitedetail. Amber frequentlypreserved the remains ofdelicate insects that areotherwise very poorlyrepresented in the fossilrecord. This fossil resin is usually associated withcoal and shale deposits. TheBaltic coast, the Isle of Wight,and New Zealand are well-known amber locations.

The ancestry of the conifers stretches back tothe forests of the Carboniferous, and thesetrees are still very much in evidence today.Conifer trees grew to an average height of 98 ft (30 m), and had long, slendertrunks. Some ancient conifers, such asSequoia, reached heights of about 230 ft(70 m), and formed extensive forests in subtropical regions. Today, theseconifers are restricted to coastalCalifornia. In temperate climates,conifer trunks terminated in needle-shaped leaves, while in tropical climatesthe leaves were flat and broad. Seedswere contained in cones, which oftenbecame carbonized (reduced to carbon)or silicified, and preserved as robustfossils. Some species of conifer, such as the Araucaria, or monkey puzzle tree, have survived with little changesince the Jurassic.

CONIFERS

Star-shaped flower

Clear amber

Trigonocarpus seeds

Silicified palm tree stem

Cycad leaves

AMBERBENNETTITALEANS

Diamond pattern ofwoody bracts on cone

Carbonized spruce cone

Carbonized flowerof Williamsonia

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REFERENCE SECTION

Swiss-American naturalist who made important studies of fossilized fish. In 1826,Agassiz was chosen to classify a large collection of fish that had been captured in theAmazon River region of Brazil.He then undertook a detailedstudy of the extinct fish ofEurope. By 1844, Agassiz hadnamed nearly 1,000 fossilfish, a pioneering work inthe study of extinct life. Bystudying the movements ofSwiss glaciers, Agassiz provedthat large sheets of ice hadcovered much of Europeduring a recent ice age.

A pioneering English fossilcollector, Anning was born inLyme Regis, England, an areafamously rich in fossils. Herfather was a carpenter andseller of fossil specimens. In 1811, Anning discovered the fossil skeleton of a Jurassicichthyosaur. This skeleton canbe seen in London’s NaturalHistory Museum. Anning went on to discover the firstplesiosaur in 1821 and the firstpterodactyl in 1828. Most of the fossils collected by Anningwere sold to institutions andprivate collections, but often no record was kept of her role in their discovery.

DOUGLAS AGASSIZ1807–73

An American father and sonteam who, in 1980, publicizedthe discovery of a worldwidelayer of clay rich in the rareelement iridium, which waspresent in rocks from the K-Tboundary, the border betweenthe Cretaceous and Paleogeneperiods. Luis (1911–88) andWalter (born 1940) argued that about 66 million years agothe iridium was deposited bythe impact of a meteorite. Theyspeculated that the catastrophicmeteoritic impact might havebeen responsible for theextinction of the dinosaurs.Luis was an experimentalphysicist who wasawarded theNobel Prize forPhysics in 1968for his work onradioactive decay.

An American paleontologistcredited with bringing aboutthe so-called dinosaurrenaissance. Bakker haspromoted a number ofrevolutionary ideas, includingthe theory that dinosaurs arehot-blooded relatives of birds,rather than cold-blooded giantlizards. His reconstructions ofdinosaurs show them standingupright, not dragging theirtails. Bakker views dinosaurs as intelligent, well-adaptedcreatures, whose extinction is problematic and intriguing.As part of his mission topopularize dinosaurs, Bakkeracted as consultant on the 1993 epic dinosaur film Jurassic Park.

ROBERT BAKKERBORN 1945

MARY ANNING1799–1847BIOGRAPHIES

A naturalist, explorer, and author who led anumber of pioneering expeditions to centraland eastern Asia. He acquired an outstandingcollection of fossils for the American Museumof Natural History (AMNH), and was itsdirector from 1934 to 1941.

After Andrews’ graduation in 1906, his firstexpeditions, undertaken for the AMNH, were toAlaska and Japan, where he studied aquatic mammals.Andrews’ most important expeditions, however, tookplace between 1919 and1930, when he traveled tothe Gobi Desert, OuterMongolia. Duringthese expeditions,Andrews’ teamsdiscovered the firstknown fossilized dinosaurnests and hatchlings. Histeams also discoveredprehistoric mammals andmany new dinosaurs,including Protoceratops,Oviraptor, andVelociraptor.

ROY CHAPMAN ANDREWS1884–1960

LUIS AND WALTERALVAREZ

An American paleontologistwho, in 1956, discovered the two-billion-year-oldPrecambrian gunflint fossils.The silica-rich flint rocks ofOntario contain some of thebest-preserved Precambrianmicrofossils in the world. In1968, Barghoorn showed thatfossils of biomolecules, such asamino acids, can be preservedin three-billion-year-old rocks.

ELSO BARGHOORN1915–1984

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BIOGRAPHIES

A Harley Davidson-riding fossil collector, who played akey role in the excavations at Home Quarry, Wyoming – oneof the world’s greatest deposits of dinosaur bones. In the 1930sand 1940s, Bird worked for theAmerican Museum of NaturalHistory as a field collector. In 1938, he found sauropodtracks near the Paluxy River,Texas. This find indicated that sauropods walked on land and refuted the beliefthat these giant animals were aquatic dinosaurs. Bird was also one of the firstscientists to find evidence of herding behavior amongthe dinosaurs.

ROLAND T. BIRD1899–1978

Briggs is known for hiswork on the Burgess Shale, a 530-million-year-old mudstone deposit inBritish Columbia, Canada.He described a number of arthropods found there, including Perspicarisand Sanctacaris. He alsodiscovered, with others, a number of new BurgessShale sites, which showedthat these animals werecommon inhabitants of the Cambrian seas. Briggs has also pioneered research into the fossilization of soft-tissue animals.

The Austrian geologist andpaleontologist Barrandeworked as a tutor to the Frenchroyal family, and followed theminto exile in Prague in 1830.Barrande dedicated himself to the study of the Paleozoictrilobite fossils of Bohemia. Hepublished the first volume ofhis life’s work – The SilurianSystem of Central Bohemia – in1852. The initial publicationwas followed by 23 volumes of text and plates.

JOACHIM BARRANDE 1799–1883 Mongolian paleontologist

and director of the Institute of Geology at the MongolianAcademy of Sciences, Barsbold discovered many new dinosaurs, namingAdasaurus and Enigmosauridae in 1983, Conchoraptor in 1985, Anserimimus in 1988, and Nomingia in 2000. Barsboldia, a 30-ft (10-m) long,duck-billed dinosaur, which lived in Mongolia in the LateCretaceous, was named afterBarsbold in 1981 by his fellowscientists Teresa Maryanska and Halszka Osmólska.

RINCHEN BARSBOLD BORN 1935

The greatest dinosaur hunterof the 20th century, whose mostfamous discovery was the firstspecimen of Tyrannosaurus rexever found. From 1910 to 1915,Brown recovered a spectacularvariety of complete dinosaurskeletons from the Red DeerRiver in Alberta, Canada. Thesediscoveries amounted to severallarge skeletons, representing 36 species of dinosaur and 84 species of other vertebrates. In the 1930s, Brown excavateda wealth of Jurassic fossils at Howe Ranch, Wyoming. Always impeccably dressed,Brown combined a greatenthusiasm for dinosaur fossils with a canny businesssense. He could generate hugepublicity and, with it, funding.As a representative of theAmerican Museum of NaturalHistory, Brown acquired fossilsfrom all over the world.

BARNUM BROWN1879–1968

An enthusiastic fossil collector from an early age,Beebe became curator of ornithology at New YorkZoological Gardens in 1899. In 1909, he embarked on a 17-month-long journey to 22 countries to studypheasants, and produced a monumental work on the subject. In 1915, Beebe described a hypotheticalancestor to Archaeopteryx, which he called Tetrapteryx.He also proposed that ornithomimosaur dinosaurswere insectivores. Beebe became an enthusiastic diver in the late 1920s. He designed the bathysphere –a steel-hulled diving sphere moored to the ocean’ssurface – to allow the exploration of deep waters.

A noted American biologist and explorer, and a writer on natural history who proposedtheories about birds’ early ancestors. In 1934,he descended, along with Otis Barton, in abathysphere to a record depth of 3,028 ft(923 m) in the waters off Bermuda.

WILLIAM BEEBE1877–1962

Beebe in 1932,standing next tohis bathysphere.

DEREK BRIGGSBORN 1950

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English paleontologist whorevolutionized theories abouttetrapods, the first vertebrateanimals with legs. Clack’sexamination of Devonian fossilsrevealed that legs evolved fornavigating in water and laterbecame adapted for walking on land. Clack discovered a complete specimen ofAcanthostega in the 1980s, andin 1998 she described Eucritta.

English biophysicist who, alongwith James Watson and MauriceWilkins, won the Nobel Prizefor Physiology and Medicine in 1962 for his determinationof the molecular structure ofdeoxyribonucleic acid (DNA).This was one of the mostimportant scientific discoveriesof the 20th century. Theirdouble-helix model of DNAhelps scientists track theevolution of extinct creatures.DNA can be used to test therelationships between animalslong extinct and to comparethem with modern relatives.From 1976 until his death,Crick was distinguishedprofessor of biological studiesat the Salk Institute, California.

JENNIFER CLACKBORN 1947

FRANCIS CRICK1916–2004

Argentinian paleontologist who is curator of vertebratepaleontology at the Los AngelesCounty Museum. Chiappe isone of the world’s leadingauthorities on ancient birds,and on the relationshipbetween birds and dinosaurs.In 1998, while working in the Río Colorado region ofPatagonia, Chiappe’s teammade a major discovery. They unearthed thousands of dinosaur eggshells, alongwith the first dinosaur embryosto be found in the southernhemisphere, and the firstconclusively identified eggsbelonging to sauropods.

ERIC BUFFETAUTBORN 1950

LUIS CHIAPPEBORN 1962

GEORGES-LOUIS DE BUFFON1797–1888

French naturalistand popularizer

of naturalhistory. His treatiseHistoireNaturelle(NaturalHistory) hasappeared

in severaleditions, and

it has beentranslated into

many languages.

Buffon’s skill was to express complex ideas in a clearform. In 1739, he became keeper of the Jardin du Roi and the royal museum in Paris, and began tocollect materials for his great work. The volume of his celebrated Natural History that appeared in 1749 was the first of 44, their publication extending over 50 years. Beautifully illustrated, the volumes are highlyprized by collectors, but the work caused a sensationwhen it was first published. The most famous volume,Epoques de la nature (Natural Epochs), was the fifth in the series and appeared in 1799. The final eightvolumes did not appear until after Buffon’s death.

EDWARD DRINKER COPE1840–97

A prolific American paleontologist whodiscovered more than 1,000 species of extinct vertebrates in the US.

From 1864 to 1867, Cope was professor ofcomparative zoology and botany at Haverford College,Pennsylvania. He devoted the next 22 years toexploration and research, concentrating on the areabetween Texas and Wyoming, where he discoveredseveral extinct species of fish, reptiles, and mammals.While working for the US Geological Survey as apaleontologist, Cope studied the evolutionary historyof the horse and of mammal teeth. Cope publishedmore than 1,200 books and papers, and contributedgreatly to the understanding of Tertiary vertebrates.

Leading French paleontologistwho has worked on developing acomplete picture of dinosaurevolution in Thailand. In thatcountry Buffetaut discovered theoldest known sauropod dinosaurof the time, Isanosaurusattavipachi from the UpperTriassic, and also numerousdinosaur footprints. In his workon the Late Cretaceous dinosaursof southern France, he found thefirst European remains of agigantic pterosaur, whose wingspan was 29.5 ft (9 m). He also discovered the first LateCretaceous birds from France.Buffetaut has worked in anumber of countries, includingSpain, Canada, and Pakistan.

French mineralogist andgeologist who devised a divisionof reptiles into four orders –saurians, batrachians,chelonians, and ophidians.Working alongside GeorgesCuvier, Brongniart pioneeredstratigraphy, the examinationof successive rock layers toreveal past environmentsand life forms. In 1822,Brongniart and Cuviermapped the Tertiary strata of the Paris basin, andcollected local fossils.

ALEXANDREBRONGNIART

1770–1847

English clergyman andgeologist who dedicatedhimself to a systematicexamination of the geology of Great Britain. In 1819,Buckland discovered the firstMegalosaurus. His first greatwork, Observations on the OrganicRemains contained in caves,fissures, and diluvial gravelattesting the Action of a UniversalDeluge, was published in 1823.Buckland’s treatise Geology andMineralogy (1836) went throughthree editions. In 1845,Buckland was appointed Deanof Westminster Abbey.

WILLIAM BUCKLAND1784–1856

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BIOGRAPHIES

EDWIN H. COLBERT1905–2001

Canadian professor of dinosaurpaleobiology at the University ofAlberta, and research scientistat the Royal Tyrell Museum of Paleontology in Drumheller.He was one of the describers of Caudipteryx, and has written a number of accessible dinosaurbooks, including DinosaurRenaissance (1994) and Newestand Coolest Dinosaurs (1998).Currie’s research specializes inPermian fossil reptiles includingdiapsid reptiles from Africa and Madagascar, and earlykinds of synapsids from Europeand the US.

CHARLES DARWIN1809–82

English naturalist who influenced scientificthought through his theory of evolution.

In 1831, Darwin traveled to the Galápagos Islandsaboard the HMS Beagle, as naturalist for a surveyingexpedition. His observations on the relationshipbetween living animals, newly extinct animals, andfossil finds led him to speculate that species evolved bya process of natural selection. When Darwin’s theorieswere first published in 1859, in On the Origin of Speciesby Natural Selection, a storm of controversy arose. Thescientific debate increased when Darwin developed hisideas in The Descent of Man (1871). Darwin’s theoriesare now a cornerstone of paleontological research.

PHILIP J. CURRIEBORN 1949

French naturalist and founderof comparative anatomy who led the way in thereconstruction of vertebrateanimals, and was an earlyproponent of stratigraphy.Cuvier dedicated himself tocomparative anatomy and tothe systematic classification of mollusks, fish, and fossilmammals and reptiles. Heproduced a number ofcomprehensive works on thestructure of living and fossilanimals, and believed that thedevelopment of life on Earthwas greatly affected by periodiccatastrophes. With AlexandreBrongniart, he explored thegeology of the Paris Basin using the newly developedprinciple of stratigraphy.

American geologist,mineralogist, and zoologistwho made important studiesof mountain-building, volcanicactivity, and the origin andstructure of continents andoceans. Dana was a geologist on a US expedition to thePacific Ocean during 1838–42,and later became a professorat Yale University. Dana’sreputation was made by a number of definitive texts, including System ofMineralogy (1837) and Manual of Geology (1862).

South African anthropologistand paleontologist whosediscovery of fossil hominids in Africa greatly contributed to an understanding of humanevolution. In 1924, Dartrecovered the “Taung” skullfrom a region near the KalahariDesert. He recognized itshumanlike features and namedthe new species Australopithecusafricanus. His claim that thisspecies had dental features and an upright posture thatapproached that of humans wasinitially met with scepticism.Later finds in South Africa andin Tanzania’s Olduvai Gorgeconfirmed Dart’s theory.

RAYMOND DART1883–1988

JAMES DWIGHT DANA1813–95GEORGES CUVIER

1769–1832

American paleontologist, whose research into vertebratepaleontology took him all overthe world, and made him oneof the foremost paleontologistsof the 20th century. Colbert’sWandering Lands and Animals(1973) studied fossils of similar land animals on differentcontinents, and addedbiological support to the theoryof continental drift, proposedby Alfred Wegener. In 1947, he excavated the Ghost Ranchsite in New Mexico, where hefound more than 500 skeletonsof Coelophysis, which lived some220 million years ago.

Skull of Homo erectusfrom Kenya, also called H. ergaster.

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Belgian paleontologist who was responsible for the firstreconstruction of Iguanodon. In1878, Dollo worked alongsideLouis De Pauw to study thefamous Iguanodon skeletonsfound in a coal mine at thevillage of Bernissart in Belgium.In 1893, Dollo proposed the Law of Irreversibility

in Evolution, which argues that complexstructures cannotbe regained intheir originalform once thatform is lost.

Welsh paleobotanist whodiscovered the earliest fossils ofvascular plants in Silurian rocksin Britain. Edwards studies theSilurian and Devonian plantfossils found in South Wales,the Welsh Borders, andScotland. She has shown howvascular plants, which use rootsto obtain water and nutrients,evolved and colonized the land.

LOUIS DOLLO1857–91

Chinese paleontologist and prolific dinosaur hunter. As a student in the 1950s, Dong studied under the fatherof Chinese paleontology, Yang Zhongdian. Dong hasbecome China’s most famouspaleontologist, and has ledfossil-finding expeditions to the Gobi Desert, Mongolia, and China’s Yunnan province.Among Dong’s many Asian discoveries areYangchuanosaurus (1978),Chungkingosaurus (1983),Alxasaurus (1993), andArchaeoceratops (1998).

DIANNE EDWARDSBORN 1942

American paleontologist who, while working for the Carnegie Museum inPittsburgh, discovered 350 tons(355 tonnes) of fossilizeddinosaur skeletons at theCarnegie Quarry in Utah (nowrenamed the Douglass Quarry).He spent many years diggingup the skeletons and shippingthem to Pittsburgh. Among his discoveries were specimensof Allosaurus, Apatosaurus,Diplodocus, and Stegosaurus.

EARL DOUGLASS1862–1931

American paleontologist and zoologist who researchedthe function of Stegosaurus’splates, and the shape andfunction of theropod teeth.Farlow is also interested in dinosaur footprints,

and has measured the feet of bird, theropod, and ornithopod skeletons inmuseums all around the world.

JIM FARLOWBORN 1951

English paleontologist who has named a number of dinosaurs, includingLesothosaurus (1978) andAliwalia (1985). Galtonsuccessfully demonstrated that hadrosaurs did not dragtheir tails, but used them tocounterbalance their heads. In the 1970s, Galton suggestedthat birds and dinosaurs shouldbe grouped as the Dinosauria.

PETER GALTON BORN 1942

American paleontologist who is professor of geology andgeophysics at Yale University,and curator of vertebrates inthe Peabody Museum. Gauthierhas worked extensively on the evolution of lizards, birds, and crocodilians.Gauthier has examined many characteristics of birds to show that they are part ofthe dinosaur family tree.

JACQUES GAUTHIERBORN 1948

EUGENE DUBOIS1858–1940

Dutch anatomist and geologist whodiscovered the remains of Java Man, the first-known fossils of the early human Homo erectus.

NILES ELDREDGEBORN 1943

American paleontologist whose work focuseson achieving a better “fit” between the fossilrecord and evolutionary theory.

In 1972, Eldredge and Stephen Jay Gould launchedthe theory of punctuated equilibria, which proposesthat new species are created from a series of rapidbursts interposed with long periods of little change,rather than by steady evolution over time.

Originally an anatomy lecturer, Dubois becameincreasingly interested in human evolution. In 1887,he traveled to the East Indies to look for hominidremains, and in 1891, at Trinil, Java, he found ahominid jaw fragment, skullcap, and thighbone. The million-year-old specimen had distinctive brow ridges and a flat, receding forehead. Dubois named itPithecanthropus (“apeman”) erectus, to show that itrepresents an intermediate stage in human evolution.

Lower toothof Iguanodon

DONG ZHIMINGBORN 1937

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BIOGRAPHIES

American paleontologist whostudied North American andAsian dinosaurs, and workedextensively in the Gobi Desert.Gilmore named severaldinosaur genera, includingAlamosaurus and Bactrosaurus.The dinosaur Gilmoreosaurus,found in China in 1979, wasnamed in his honor.

CHARLES WHITNEYGILMORE1874–1945

Australian geologist whoproduced the first detaileddescriptions of the Ediacaranfossils from the FlindersRange mountains of southernAustralia. Glaessner was thefirst to make major inroadstoward understanding thePrecambrian record ofmulticellular life. In 1961, herecognized that the Ediacaranfossils were the oldest-knownmulticelled organisms.

MARTIN GLAESSNER1906–89

One of the first paleontologistsat the American Museum ofNatural History. Granger waschief paleontologist on themuseum’s Central Asiaticexpeditions of the 1920s. In1898, Granger led theexpedition that discovered the Apatosaurus skeleton thatbecame the first sauropod everto be mounted for exhibition.

WALTER GRANGER1872–1941

American paleontologist who was an outstanding field geologist, and became geologist for New York state.Hall’s masterwork is the book The Paleontology of New York (1847–94), acomprehensive review of thePaleozoic invertebrate fossils ofthe state of New York.

JAMES HALL1811–98

German biologist andoutstanding field naturalist whowas the first prominent Germanto support Darwin’s theories ofevolution, which he promotedenthusiastically in Germany.Haeckel was the first to draw up a genealogical tree layingout the relationship betweenthe various orders of animals.He coined the word “phylum”for the major group to whichall related classes of organismsbelong. He traced the descent

of humans from single-celled organisms

throughchimpanzees and so-calledPithecanthropuserectus, which

he saw as the linkbetween apes andhuman beings.

ERNST HAECKEL1834–1919

STEPHEN JAY GOULD1941–2002

American paleontologist, biologist, andscience writer, whose popular books tracevarious controversies in the history ofevolutionary biology and paleontology.

Gould’s early work at Harvard University focused on the evolution of West Indian land snails. He laterdeveloped the theory of punctuated equilibria withNiles Eldredge, which proposes that new species arecreated from a series of rapid bursts interposed withlong periods of little change. Gould wrote many

popular works, including Time’s Arrow, Time’sCycle (1990), which examines the

measurement of Earth history.

Gould explored the reasons for the extinction ofdinosaurs in his

book Bully forBrontosaurus

(1991).

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REFERENCE SECTION

Paleontologist fromQueensland, Australia, best known for her work on Paleozoic corals. In herearly fieldwork, Hill outlinedthe structure of Mesozoicsediments in the BrisbaneValley. She became interestedin corals while working on a Carboniferous fossil reef at Mundubbera. Hill went on to write three volumes of The International Treatise on Invertebrates, which wonscientific acclaim worldwide.

GERHARD HEILMANN1859–1946

Scottish geologist who soughtto understand the history of the Earth by studying theorigins of minerals and rocks.In his Theory of the Earth (1785),Hutton argued that the presentrocks of the Earth’s surfacewere formed from the waste of older rocks. He traced thedynamic processes that shapethe land and the processes of erosion that flatten it.

JAMES HUTTON1726–97

DOROTHY HILL1907–97

The first great, moderndinosaur tracker, Hitchcockdescribed thousands ofdinosaur tracks, many from his native New England, but he never attributed thesetracks to dinosaurs. Instead,Hitchcock theorized that thetracks belonged to large extinctbirds. In the late 20th century,it was argued that birds are thedirect descendants of a groupof carnivorous dinosaurs knownas coelurosaurs. Hitchcock hadstumbled onto a connection –his tracks were in fact made bythe ancient theropod relativesof birds. In his work Hitchcockaccumulated an impressivecollection of Early Jurassictracks, many of which are stillon display at Amherst Collegein Massachusetts.

EDWARD HITCHCOCK1793–1864

WILLI HENNIG1913–76

A German zoologist and supporter of thetheory of cladistics, which groups organismsaccording to the historical sequence by whichthey descended from a common ancestor.

Hennig used his early research on the larvae ofDiptera, an order that includes flies and mosquitoes,to refine his cladistics theory. In 1949, Hennig becamehead of the systematic entomology department inLeipzig. In 1950, he proposed his cladistics principlesin the book Phylogenetic Systematics. The erection of the Berlin Wall in 1961 drove him to West Germany,where he became director of phylogenetic research at the Museum of Natural History in Stuttgart.

FERDINAND HAYDEN1829–87

American geologist whose bold exploration of the western territories of the US led to the first finds of horned dinosaurs.

Hayden’s love of exploration began in the early 1850s.During his geological surveys conducted for the USgovernment, Hayden collected fossils and recordedthe geological composition of the western territories.

His geological survey of theUpper Missouri in 1855produced the first finds ofTroodon and Palaeoscincus.

Danish doctor who wrote TheOrigin of Birds (1916), whichexamined the similaritiesbetween theropod dinosaursand birds. Heilmann thoughtthat theropods lackedcollarbones, and concludedthat they could not be birds’ancestors since a feature couldnot vanish and later reappearduring evolution. His theorywas unchallenged by scientistsuntil the discovery of dinosaurswith collarbones.

Hayden atcamp duringa survey,

c. 1874

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BIOGRAPHIES

Vertebrate paleontologist andprofessor in the department of organismal biology andanatomy at the University of Chicago, Hopson hasresearched the evolutionaryhistory of the synapsids, a majorbranch of the vertebrates. He is interested in tracing thestructural changes thatoccurred during the evolutionfrom Late Paleozoic synapsidsto the more modern mammalsof the Late Mesozoic. In hiswork, Hopson has estimateddinosaur brain size and hasproposed theories on thefunction of hadrosaurid crests.

JAMES HOPSONBORN 1935

American paleontologist and Curator of Paleontology at the Museum of the Rockiesin Montana. In 1978, Hornerdiscovered the fossilizedskeleton of a duck-billed baby Maiasaura dinosaur in Montana. He also excavateda cache of dinosaur nests found at Egg Mountain,Montana. Horner has proposeda number of new theoriesabout dinosaurs, most notablythe idea that some dinosaurparents nurture theirhatchlings. He has also arguedthat Tyrannosaurus rex was not adeadly hunter, but was, in fact,a scavenger that ate carrion.

JOHN HORNERBORN 1946

Physical anthropologist whodiscovered the first knownskeleton of Australopithecusafarensis. In 1973, Johansonfound the knee-joint of anaustralopithecine in Ethiopia.He was able to demonstratethat these hominids walked in an upright fashion, likehumans. The following year, he discovered “Lucy”, the oldest fossilhominid ever found.

DONALD JOHANSONBORN 1943

Polish paleontologist who was the first woman toorganize and lead fossil-huntingexpeditions to the Gobi Desert,conducted from 1963 to 1971.In Mongolia, Kielan-Jaworowskadiscovered Cretaceousdinosaurs and rare finds ofMesozoic mammals. Her bookHunting for Dinosaurs (1969)popularized the paleontologyof the Gobi region. She haspublished more than 200scientific papers, as well as many books and articles.

ZOFIA KIELAN-JAWOROWSKA

BORN 1925

Famous dinosaur illustratorwho worked at the AmericanMuseum of Natural History’sdepartment of vertebratepaleontology during the 1920sand 1930s. Knight’s interest indrawing wild animals eventuallyled to his association with themuseum, where he studied andreconstructed the appearanceof extinct animals. His mostfamous murals are Life in an Ice Age (1911–21) and The Ageof Mammals in North America,which was completed in 1930.

CHARLES KNIGHT1874–1953

Pioneering Canadianpaleontologist and fossil hunter who investigateddinosaur fossils in the Albertaregion for the CanadianGeographical Survey. Lambenamed Euoplocephalus (1910),Chasmosaurus (1914), andEdmontosaurus (1917). Thedinosaur Lambeosaurus lambei,which was discovered byCharles H. Sternberg in 1913,was named in Lambe’s honour.

LAWRENCE LAMBE1863–1919

THOMAS HUXLEY1825–95

English biologist who supported the ideas of Charles Darwin, and recognized theanatomical links between birds and reptiles.

The young Huxley voyaged to the Torres Strait wherehe studied ocean life. Darwin’s theories enthused him,and he rebuffed many of Darwin’s critics in a series of papers and lectures. Huxley studied fossil reptilesand birds, and in 1867 he linked them in an orderthat he called Sauropsida to demonstrate their closerelationship. He listed several characteristics that areshared between typical dinosaurs and modern birds.

JEAN-BAPTISTE DE LAMARCK1744–1829

French naturalist who developed ideas oninvertebrates and the diversity of animal life.

As botanist to the king of France, Lamarck producedcomprehensive botanical works. He was the first to use the presence of a vertebral column to distinguishbetween vertebrate and invertebrate animals. Lamarck was also a pioneer in evolutionary theory. Hepromoted the idea that species were not unalterable,and that more complex forms developed from pre-existent, simpler forms. Lamarck also developed atheory on the inheritance of acquired characteristics.

Johansonholds the skullof “Lucy”, a3.1-million-year-oldhominid.

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Leading expert on dinosaurtrackways, professor of geologyat the University of Colorado,and curator of the DenverFossil Footprint Collection.Lockley’s primary researchinterests include fossilfootprints, dinosaur trackways,and paleontological history. Hisresearch has taken him fromhis home bases of Coloradoand Utah to Europe, andCentral and East Asia.

WILLARD LIBBY1908–80

MARTIN LOCKLEYBORN 1950

MARY AND LOUIS LEAKEY

A husband and wife team whose fossil findsproved that human evolution was centered

on Africa, and that the humanspecies was older than hadbeen thought.

CAROLUS LINNAEUS1707–78

American chemist whosemethod of radiocarbon dating proved an invaluabletool for paleontologists andarcheologists. As part of theManhattan Project (1941–45),Libby helped to develop amethod for separating uraniumisotopes. In 1947, he discoveredthe isotope Carbon-14. Itsdecay within living organisms isused to date organic materials,such as shell and bone. Libbywas awarded the Nobel Prizefor Chemistry in 1980.

American scientist who wasprofessor of anatomy at theUniversity of Pennsylvania. Awell-respected anatomist and aspecialist on intestinal parasites,Leidy became famous as avertebrate paleontologist. He examined many of thenewly discovered fossil findsfrom the western states and, ina series of important books andpapers, laid the foundations ofAmerican paleontology. HisExtinct Fauna of Dakota andNebraska (1869) containedmany species unknown toscience and some that werepreviously unknown on theAmerican continent.

An Italian dinosaur expert who became a paleontologistwhile studying to become apriest. Leonardi traveled toBrazil in the 1970s in search ofmeteorites, and later returnedthere to live. He has traveled to the most remote terrain inSouth America in search ofdinosaur tracks from differentperiods. He also discoveredwhat may be one of the world’soldest tetrapod tracks, datingfrom the Late Devonian. Hehas mapped remote sites ininaccessible locations, and has synthesized informationabout fossilized footprints on a continental scale.

JOSEPH LEIDY1823–91

GIUSEPPE LEONARDIDATES UNAVAILABLE

Louis Leakey (1903–72) was born in Kenya of Englishparents. In 1931, he began work in the Olduvai Gorge,Tanzania, aided by his second wife, Mary (1913–98),an English paleoanthropologist. In 1959, Marydiscovered a 1.7-million-year-old fossil hominid, nowthought to be a form of australopithecine. Between1960 and 1963, the Leakeys discovered remains of Homo habilis, and Louis theorized that their find was a direct ancestor of humans.

CarolusLinnaeus

Swedish botanist whose Systema naturae(1735) laid the foundations for theclassification of organisms.

Linnaeus was the first to formulate theprinciples for defining genera andspecies. He based a system of classification on his closeexamination of flowers. Thepublication of this system in 1735 was followed by the appearance of GeneraPlantarum (1736), a work that is considered the startingpoint of modern botany.

The Leakeys holda 600,000-year-old skull found inTanzania, CentralAfrica.

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BIOGRAPHIES

English naturalist and geologistwho catalogued the fossilmammals, reptiles, and birds inthe British Museum. Lydekker’smagnificent 10-volume set ofCatalogues was published in1891. In 1889, he published the two-volume A Manual ofPalaeontology together with H.A.Nicholson. Lydekker was alsoresponsible for naming thedinosaur Titanosaurus (1877).

STANLEY MILLER1930–2007

American chemist who conductedexperiments in the 1950s to demonstrate the possible origins of life on Earth.

While working in Chicago in 1953, the 23-year-oldMiller passed electrical discharges – equivalent to asmall thunderstorm – through a mixture of hydrogen,methane, ammonia, and water, which he believedrepresented the constituents of Earth’s earlyatmosphere. After some days, his analysis showed the presence of organic substances, such as aminoacids and urea. Miller’s experiments revolutionizedscientific understanding of the origins of life on Earth.

RICHARD LYDEKKER1849–1915

Scottish barrister and geologistwho studied the geology ofFrance and Scotland, and in1827 gave up a career in law fora life spent studying geology. Inhis work The Principles of Geology(1830–33), Lyell devised thenames for geological epochsthat are now in universal usage,including Eocene and Pliocene.His Elements of Geology, whichwas published in 1838, becamea standard work on stratigraphyand paleontology. In Lyell’sthird great work, The Antiquityof Man (1863), he surveyed thearguments for humans’ earlyappearance on Earth, discussedthe deposits of the last Ice Age, and lent his support toDarwin’s theory of evolution.

CHARLES LYELL1797–1875

American paleontologist whoworked extensively on the fossilrecord of mammals. Matthewwas curator of the AmericanMuseum of Natural Historyfrom the mid-1890s to 1927.One of his key theories, thatwaves of faunal migrationrepeatedly moved from thenorthern continents southward,mistakenly relied on the notionthat the continents themselveswere stable. Matthew also didearly work on Allosaurus andAlbertosaurus, and on the earlybird Diatryma. He namedDromaeosaurus in 1922. He was one of the first to study theeffect of climate on evolution.

German paleontologist who named and describedArchaeopteryx (1861),Rhamphorhynchus (1847), and Plateosaurus (1837). Meyerwas one of the first to viewdinosaurs as a separate group,which he called “saurians” in 1832. Meyer startedpublication of the journalPaleontographica in 1846, andused it to publish much of hisresearch on fossil vertebrates.

American paleontologist andpioneer of dinosaur studies.Marsh described 25 new generaof dinosaurs and built up oneof the most extensive fossilcollections in the world. After studying geology andpaleontology in Germany,Marsh returned to America and was appointed professor ofpaleontology at Yale Universityin 1860. He persuaded hisuncle, George Peabody, toestablish the Peabody Museumof Natural History at Yale. Onscientific expeditions to thewestern United States, Marsh’steams made a number ofdiscoveries. In 1871, they foundthe first American pterosaurfossils. They also found theremains of early horses in the US. Marsh described the remains of Cretaceoustoothed birds and flyingreptiles, and Cretaceous andJurassic dinosaurs, includingApatosaurus and Allosaurus.

OTHNIEL CHARLESMARSH1831–99

WILLIAM DILLERMATTHEW1871–1930

HERMANN VON MEYER1801–69

Stanley Miller with the glass apparatusused to recreate theconditions found on primitive Earth.

REFERENCE SECTION

American paleontologist who is chairman and curator ofvertebrate paleontology at theAmerican Museum of NaturalHistory, who has carried outextensive fieldwork inMongolia. In 1993, Norell andMichael Novacek discovered asite in the Gobi Desert calledUkhaa Tolgod, a basin rich in fossils. Therethey found an 80-million-year-old fossil oviraptorid embryostill cloaked in shatteredeggshell, as well as a matureoviraptorid that had beenburied while sitting on a nest of eggs. In 1995, Norell found a dromaeosaur nest containingeggs, which had been buried bya prehistoric sandflow. He hasworked with Chinese colleaguesto describe feathered dinosaursfrom Liaoning, China.

HENRY FAIRFIELD OSBORN1857–1935

American paleontologist who greatlyinfluenced the art of museum displayand made important contributions to the study of dinosaurs.

Osborn was president of the American Museum of Natural History (AMNH) from 1908 to 1935, andwas also professor of zoology at Columbia Universityfrom 1896 to 1935. During his tenure at the AMNH,he accumulated one of the finest fossil collections in the world and was a celebrated popularizer ofpalaeontology. In 1905, he described and namedTyrannosaurus rex. Osborn proposed the concept ofadaptive radiation – that primitive plants or animalsmight evolve into several species by spreading over alarge area and adapting to different ecological niches.

RODERICK MURCHISON1792–1871

Scottish geologist who pioneered the mapping and study of Paleozoic rocks. He also defined and named the Silurian and Devonian systems.

Originally a soldier, Murchison prepared his firstpaper for the Royal Geological Society in 1825. WithCharles Lyell and Adam Sedgwick as his companions,he explored France, Italy, and the Alps to study theirgeology. Investigations into the geology of the Welshborders led, in 1839, to his establishment of theSilurian system – a series of rock formations, each

containing distinctiveorganic remains,

which can be foundall over the world.

Investigations in southwesternEngland andthe Rhinelandled to thedefinition ofthe Devonian

system. Furthergeological

expeditions tookhim to Russia and

the Scottish highlands.

ALEXANDER OPARIN1894–1980

Russian biochemist who studiedthe origins of life from organicmatter. Oparin theorized that simple organic andinorganic materials might havecombined into complex organiccompounds, which, in turn,formed primordial organisms.His most important work is TheOrigin of Life on Earth (1957). In1935, Oparin helped to found abiochemical institute in honor of his mentor, the botanist A.N.Bakh. He remained director of the institute until his death.

JOHN OSTROM1928–2005

American vertebratepaleontologist who became professor emeritus of geologyat Yale University. Ostrom was a specialist in the evolution of birds, and argued that birdsevolved from warm-bloodeddinosaurs. He made a revolutionary study of thedinosaur Deinonychus, which he and others discovered in1964. Ostrom named thedinosaurs Microvenator,Tenontosaurus, and Sauropelta.

RICHARD OWEN1804–92

English anatomist andpaleontologist who coined the word “dinosaur” in 1842. Owen was responsible for the foundation of the Museum of Natural History in South Kensington, London. Trained as a doctor, he went on to become an expert incomparative anatomy. In 1856,he became superintendent ofthe natural history departmentof the British Museum. Hesupervised the removal of thecollections to a new building in South Kensington. A pioneerin vertebrate paleontology, heconducted extensive researchon extinct reptiles, mammals,and birds. His most importantwork in this field is his four-volume History of British FossilReptiles (1849–84). Owen wasresponsible for the first full-scale dinosaur reconstructions,which were displayed in CrystalPalace Gardens, London.

KEVIN PADIANBORN 1951

Professor of integrative biology who is curator in the Museum of Paleontology at the University of California. Padian is one of the world’sleading authorities on theevents that took place duringthe transition from the Triassicperiod to the Jurassic period, a time that signalled the rise of the dinosaurs. He has writtenextensively on the relationshipof birds to dinosaurs, andstudies pterosaurs to see whattheir anatomy illustrates aboutthe origins of flight. Padian also studies fossil footprints,and is interested in the history of paleontology.

MARK NORELLBORN 1957

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English clergyman andgeologist who became the Woodwardian professor of geology at CambridgeUniversity. Sedgwick carried out extensive fieldwork insouthwestern England, the Isle of Wight, and Yorkshire.Following fieldwork in Wales in 1831, he applied the nameCambrian to the oldest groupof fossiliferous strata. In 1836,while working with RoderickMurchison, Sedgwickdemonstrated that the fossilsof the Devon limestoneswere of an intermediate type,between those of the Silurianand Carboniferous systems.They introduced the nameDevonian for the slates andlimestone of southwesternEngland, and jointlypublished On the PhysicalStructure of Devonshire, a memoir.

An American paleontologist known for hisfieldwork and research on early dinosaurs.

Attached to the University of Chicago, Sereno hasworked extensively in South America, Asia, and Africa.He named one of the earliest dinosaurs, Eoraptor, andfound the first complete skull of Herrerasaurus. In

1994, Sereno found and named thepredatory African dinosaurAfrovenator. He has alsorearranged dinosaurcladograms – in particular, the ornithischian groupings.

PAUL SERENOBORN 1957

BIOGRAPHIES

ADAM SEDGWICK1785–1873

HARRY GOVIER SEELEY1839–1909

Seeley was the pioneer, in 1887, of a radical new dinosaurclassification scheme. Henoticed that all dinosaurspossessed a pelvis that followedone of two distinctive designs –birdlike or reptilelike. Hedivided the dinosaurs into two orders, Ornithischia (“bird-hipped”) and Saurischia(“reptile-hipped”). In his bookDragons of the Air (1901), Seeleyassessed early research andopinion on pterosaurs.

ALFRED SHERWOOD ROMER1894–1973

American paleontologist who is known for his theories about vertebrate evolution.

Romer saw anatomical adaptations to environmentalchange as the key to evolutionary progress. In 1933,he became professor of biology at Harvard Universityand published Vertebrate Paleontology, an importantwork that shaped academic thinking for decades.

French professor ofcomparative anatomy who is known for his research ondinosaur bone structure. Usingthe link between bone structureand rate of bone growth,Ricqlès examined the structureof fossil bones. His findings led him to suggest that certaingroups of dinosaurs might havebeen warm-blooded, a theorythat is a popular topic ofdebate among paleontologists.

ARMAND DE RICQLÈSBORN 1938

Paul Sereno studiesdinosaur skeletonsfrom around the worldto learn more aboutdinosaur evolution.

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REFERENCE SECTION

A Danish scientist andphysician to Ferdinand II who recognized the organicprocesses that fossilize bone, and contributed to thecreation of laws on the datingof sedimentary rock strata. In 1666, Stensen examined ashark’s skull and observed thatorganic processes had turnedthe teeth – which he called“tongue stones” – to stone.From these observations,Stensen developed anunderstanding of theprocesses of fossilization.Stensen also drew stratigraphicsections of the rocks in theTuscany region. He hastherefore been seen as the father of both modernpaleontology and geology.

American paleontologistand professor in thedepartment of ecologyand evolution at the University ofChicago, Van Valen has pointed out thesimilarities between themesonychid mammals

of the Paleocene epochand the early whalescalled protocetids. Hehas also proposed anecological successionmodel for the extinction of the dinosaurs.

NIELS STENSEN1638–86

An important paleontologistand the author of hundreds oftechnical papers and popularbooks, Simpson was curator ofthe department of geology andpaleontology at the AmericanMuseum of Natural Historyfrom 1945 to 1959. An experton the Mesozoic era and thePaleocene epoch, Simpson wasone of the first paleontologiststo make use of genetics andstatistical analysis. He studiedthe extinct mammals of SouthAmerica, and contributedmuch to the understanding of transcontinental migration.

Australian geologist whodiscovered the then oldest-known fossils in 1946. Spriggstumbled across the 560-million-year-old Precambrianfossils in the Ediacaran Hills of the Flinders Range in SouthAustralia. Since their discovery,“Ediacaran” fossils have beenfound all over the world. Sprigg continued to pursue his geological career, and ledoil exploration in Australia. He mapped the Mount Painteruranium field for the SouthAustralian Geological Survey in 1944.

Led by their father, Charles H.(1850–1943), the Sternbergfamily made many spectaculardinosaur discoveries in NorthAmerica. In the 1860s, CharlesH. discovered thousands of fossils, and developedtechniques for “jacketing” fossil bones in a protective cast. Charles M. (1885–1981)was famous for his ability to“read” the ground for dinosaurbones. George (1883–1959)discovered the duck-billedEdmontosaurus (1909). Levi(1894–1976) developed a latex casting technique that was used to duplicate fossils.

GEORGE GAYLORDSIMPSON1902–84

REG SPRIGG1919–94

THE STERNBERGFAMILY

WILLIAM SMITH1769–1839

English geologist who is known as the “fatherof English geology.” He was a pioneer ofgeological mapping and stratigraphic geology.

Smith was a canal engineer who studied rocks whilecarrying out engineering surveys around England. He realised that particular rock layers (strata) could

be identified by the fossils theycontained. By taking vertical

sections and identifying rockoutcrops at the surface, Smithwas able to produce three-dimensional geological maps. In 1794, he produced his firstgeological map, of the region

around Bath. In 1815, hepublished a 15-sheet

geological map ofEngland, Wales, andpart of Scotland.

English paleobotanist,suffragette, and pioneerof birth control.

In 1905, Stopes becamethe first female sciencelecturer at ManchesterUniversity. She was an experton fossil plants andprimitive cycads,and demonstratedhow plant remainsalter to becomecoal. Stopes’slater careerwas ruled byher interestin women’shealth issues.

LEIGH VAN VALENBORN 1935

MARIE STOPES1880–1958

Marie Stopesstudied botanyin England and Germany.

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BIOGRAPHIES

American geologist whodiscovered the Burgess Shale fossils. Walcott joined the US Geological Survey, andbecame its director in 1894. He described and interpretedthe great Paleozoic region ofcentral Nevada, and examinedthe Cambrian formations of theAppalachian Mountains. Later,he worked on the Cambrianformations of the RockyMountains. In 1909, Walcottmade his most famous findwhen he discovered the depositof Cambrian fossils known as the Burgess Shale in BritishColumbia, Canada. Walcott hadunearthed the largest find ofperfectly preserved fossils fromany era. He excavated some70,000 specimens and passedthem on to the SmithsonianInstitute, of which he hadbecome head in 1907.

American molecular biologistand discoverer, with JamesCrick and Maurice Wilkins, of the molecular structure ofdeoxyribonucleic acid (DNA).For this discovery Watson was awarded the Nobel Prizefor Physiology and Medicine in 1962. He wrote about hisresearch in The Double Helix(1968). From 1989 to 1992,Watson was director of the US National Center for Human Genome Research.

CHARLES D. WALCOTT1850–1927

ALFRED WEGENER1880–1930

JAMES WATSONBORN 1928

The father of German geology,who proposed a “Neptunist”theory of geology – that theminerals present in the ancientocean that once covered theEarth were gradually depositedas rock. Werner’s belief in aprimeval ocean as the origin of all of Earth’s rocks washighly influential. His followerswere called Neptunists, whileopponents, who recognized the importance of subterraneanheat in the formation of theEarth’s crust, were known asVulcanists. A mineralogist andteacher, Werner examined therocks of Saxony to demonstrategeological succession – the ideathat the rocks of the Earth arelaid down in layers that revealthe Earth’s history. Althoughhis Neptunist ideas have beendisproven, his work on thechronological succession ofrocks is still widely respected.

American biologist,paleontologist, andentomologist, who is chiefly remembered for hiscontributions to vertebratepaleontology, in particular his monumental research on Cretaceous and Permianreptiles and amphibians.Williston found the firstDiplodocus remains in 1877, and formulated a theory on theevolution of flight. He alsoconducted extensive researchinto the Diptera – an order of insects that includes flies,mosquitoes, and midges.

English professor who built anextensive collection of fossilsand minerals, and devised oneof the earliest classifications offossils. Woodward’s collectionwas left to the University ofCambridge, and is currently on display in the SedgwickMuseum, Cambridge, England.

ABRAHAM GOTTLOBWERNER1750–1817

JOHN WOODWARD1655–1728

SAMUEL WENDELLWILLISTON1852–1918

From 1924 Wegener held the chair in meteorologyand geophysics at the University of Graz, Austria. He began to develop his theory of continental driftfrom 1910, but it was not fully articulated until thepublication of his Origin of Continents and Oceans in1929. In that book he argued that India, Africa, SouthAmerica, Australia, and Antarctica were once united in a supercontinent, which he named Pangea. Thislandmass broke up and drifted apart 200 million yearsago. Wegener’s evidence for this theory was the jigsaw“fit” of separated continents, as well as matching finds of rocks and fossils. His ideas were initially met with hostility, and only gained support with the development of plate tectonics theory.

German meteorologist and geologist whodeveloped the theory of continental drift,which revolutionized the scientific study of the Earth in the 20th century.

Wegener died, aged 50,on his third expedition tothe Greenland ice sheet.

DISPLAYS IN THE USA

DISPLAYS IN THE UK

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THE PAST ON DISPLAYMILLIONS OF FOSSILS are displayed around the world in museumsof natural history. In some countries, amateur enthusiasts canalso visit sites where fossils are being excavated. Alternatively,travel back in time by exploring websites about prehistoric life.

REFERENCE SECTION

Robotic Tyrannosaurus rex at London’s Natural History Museum

Fossil bear at the AmericanMuseum of Natural History

NATURAL HISTORY MUSEUM

Cromwell Road, London SW7You will immediately be face-to-face with a huge 85-ft (26-m)long skeleton of Diplodocus as youenter the Life Galleries at thissuperb museum. Use the touch-screens, videos, and interactiveexhibits to learn about prehistoriclife and the theory of evolution.Don’t miss the amazing roboticdinosaurs, especially the anima-tronic T-rex with its terrifyinglysharp teeth. The museum’swebsite includes virtual realityfossils and a Dino Directory,which you can search by time,country, and body shape.

OXFORD UNIVERSITY MUSEUM

OF NATURAL HISTORY

Parks Road, OxfordDinosaurs and other Mesozoicreptiles found locally, dinosaureggs from China, and a dodo areamong the fantastic sights.

SEDGWICK MUSEUM

Downing Street, CambridgeHuge ammonites, giant marinereptiles, and a prehistorichippopotamus found in a localgravel pit are among the millionfossils that have been collectedby this museum.

HUNTERIAN MUSEUM

University Avenue, GlasgowCome here to see the first andsecond dinosaur fossils ever tobe found – a tooth each fromIguanodon and Megalosaurus. Plusview finds from the Gobi Desertin Mongolia, and lots more.

DINOSAUR ISLE

Sandown, Isle of WightAn animatronic Neovenator – ameat-eating dinosaur that onceroamed the Isle of Wight – isjust one of the exciting displays.Also go on fossil walks andwatch scientists at work.

AMERICAN MUSEUM

OF NATURAL HISTORY

Central Park West, New YorkThe displays include saurischianand ornithischian dinosaurs,and extinct mammals. “Ology”on the museum’s website isespecially for children, with greatquizzes, games, and activities.

DENVER MUSEUM OF NATURE

AND SCIENCE

Denver, ColoradoTravel through 3.5 billion yearsof time in the PrehistoricJourney exhibit, and learn moreabout prehistoric creatures,including the dinosaurs. Thisexhibit features an Allosaurusand Stegosaurus battling aDiplodocus, and continuesthrough the rise of mammalsand the coming of humans.Museum touch carts hold fossilsthat can be examined by hand.

SMITHSONIAN MUSEUM

OF NATURAL HISTORY

10th Street and ConstitutionAvenue, Washington, DCAmazing dioramas recreatescenes from the Jurassic andCretaceous periods, the last IceAge, and life in the ancientseas. You are also allowed totouch and examine fossils in theDiscovery Room, and arrange to watch scientists at work in theFossil Laboratory.

FIELD MUSEUM OF

NATURAL

HISTORY

1400S.LakeShore Dr,ChicagoExhibitscover 3.8billion years of life onEarth from single cells todinosaurs and humans. Besure to visit “Sue,” the world’slargest and best preservedTyrannosaurus rex, found in 1990in the badlands of South Dakota.

LOS ANGELES COUNTY MUSEUM OF

NATURAL HISTORY

900 Exposition Blvd, Los AngelesA cast of the complete skeletonof the largest-necked dinosaurever discovered – calledMamenchisaurus – is here, andthere are also dramatic modelsof Allosaurus and Carnotaurus.Activities include fossil rubbingsin the Discovery Center.

CARNEGIE MUSEUM

OF NATURAL HISTORY

4400 Forbes Ave, PittsburghBrontosaurus, Stegosaurus, andCamptosaurus are among displaysof the largest land animals everto live. Trace the evolution ofcamels and horses, and help out in the Bonehunters Quarry.

PREHISTORIC LIFE IN CYBERSPACEDISPLAYS AROUND THE WORLD

American Museum of NaturalHistory Fossil Timelinewww.amnh.org/exhibitions/permanent/fossilhalls/Travel through a geologicaltimeline and explore fossils byevolutionary relationships inthis informative site.

Dino Datawww.dinodata.netGreat site for serious dinosaurenthusiasts, with all the facts at your fingertips.

Dino Russ’s Lairwww.dinoruss.comInformation on dinosaurs,dinosaur eggs, exhibits, digs youcan join, and sites to visit.

Dinosauria On-Linewww.dinosauria.comAward-winning site forenthusiasts, with a gallery ofimages and discussion group.

Discovering Dinosaurswww.britannica.com/dinosaurs/dinosaurs/index2.htmlFrom Encyclopedia Britannica –how our ideas about dinosaurshave changed over the years.

Imax: T-Rexwww.imax.com/t-rexBecome a virtual paleontologistand travel back through time tosuch eras as that of thelegendary Tyrannosaurus rex.

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THE PAST ON DISPLAY

The Hall of Saurischian Dinosaurs at the American Museum of Natural History, New York

THE ROYAL TYRRELL MUSEUM

OF PALEONTOLOGY

Drumheller, Alberta, CanadaSee what the undersea worldwas like in the Cambrianperiod, with its strange andexotic creatures. Primitiveplants are grown in thePaleoconservatory, and thereare great displays of Alberta’srich fossil heritage. If you can’tvisit in person, try the virtualtour on the museum’s website,which also has an A-Zencyclopedia of fossils.

CANADIAN MUSEUM OF NATURE

Ottawa, Ontario, CanadaHorned, duck-billed, and“ostrich mimic” dinosaursfeature in the exhibits, whichwere found in the badlands ofSouthern Alberta and Saskat-chewan. On the website aregames presented by the VirtualMuseum of Canada including“Dig This! the CretaceousPeriod” and “Palaeo Pursuit.”

QUEENSLAND MUSEUM

Brisbane, Queensland, AustraliaLearn about the weird prehistoriccreatures that used to roamQueensland. Quizzes to test yourknowledge about Australiandinosaurs and a poster to coloron the website.

MUSÉE PARC DES DINOSAURES

Béziers, FranceThe largest museum-park of fossils in Europe, locatedwithin a paleontological site in Southern France. Excavationnews is posted on the website,which has an English version.

ROYAL BELGIAN INSTITUTE OF

NATURAL SCIENCES

Brussels, BelgiumExhibits include the world’slargest group of Iguanodon – 30skeletons discovered in a coalmine at Bernissart in 1878.

ZIGONG DINOSAUR MUSEUM

Zigong, Sichuan, ChinaExcellent museum that is builtover the site of some incredibleexcavations. Twelve dinosaurs in good condition are displayedhere, and some bones are stillin situ. The dinosaurs aresometimes taken out of Chinaand displayed at temporaryexhibitions round the world.

ARGENTINE MUSEUM OF

NATURAL SCIENCES

Buenos Aires, ArgentinaNumerous remarkable dinosaurfossils found in Patagonia areon show at this center ofpaleontological study.

Palaeoswww.palaeos.com/In-depth information andimages about most of the majorgroups of prehistoric animalsand the times they lived.

Prehistoric Illustratedwww.prehistoricsillustrated.comGallery of prehistoric creaturesplus the latest news andresearch on extinct animals.

Sue at the Field Museumwww.fieldmuseum.org/sue/index.htmlUncover the largest,best–preserved Tyrannosaurusrex specimen yet discovered.

University of CaliforniaMuseum of Paleontologywww.ucmp.berkeley.edu/exhibits/index.phpThousands of pages of contentcovering the history of lifethrough time.

Walking with Dinosaurswww.bbc.co.uk/dinosaurDiscover a wealth ofinformation, galleries, andanimations of prehistoric life.

Zoom Dinosaurswww.EnchantedLearning.com/subjects/dinosaursAsk questions and vote for yourfavorite dinosaur, plus gamesand the best dinosaur jokes ever!

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behind the eye. Besides extinctforms, anapsids may includeturtles and tortoises.

Ancestor An animal or plant fromwhich others have evolved.

Angiosperms (AN-JEE-o-spermz:“seed vessels”) Flowering plantswhich have seeds enclosed in anovary. The group includes broad-leaved trees and grasses.

Ankylosaurs (ANG-ki-lo-SORE-z or ang-KIE-lo-SORE-z: “fusedlizards”) Four-legged, armored,plant-eating, ornithischiandinosaurs with bony plates thatcovered the neck, shoulders, andback. A horny beak was used forcropping plants.

Annelids Worms with segmentedbodies. Because they lack skeletal structures, their fossilevidence is usually restricted to trails and burrows.

Anthracosaurs(an-THRAK-o-SORE-z) Extinctamphibious tetrapods, includingkinds that mainly lived on land,may have included the ancestorsof the reptiles.

Anthropoids/the AnthropoideaThe higher primates: monkeys,apes, and humans.

Anthropology The study ofhumankind. Anthropologistsexamine and analyze thestructure of human societies andthe nature of human interactionsand beliefs.

Antorbital fenestra A hole in theskull in front of each eye; ahallmark of the archosaurs.

Appendages Limbs, gills,antennae, or other parts project-ing from a creature’s body.

Araucaria A genus of largeevergreen conifers, characterizedby small leaves arranged inspirals. Living members includethe monkey puzzle tree andNorfolk Island pine.

Archaea Primitive single-celledorganisms, thought to be amongthe earliest life forms to haveevolved, over 3.5 billion yearsago. Many thrive in extremeconditions, such as scalding water.

Archaean/Archean The secondeon of the geological timescale,about 3.8–2.5 billion years ago.

Archaic Primitive, or of an ancient time.

Archosaurs (AR-ko-SORE-z: “ruling lizards”) A major groupof reptiles that originated in theTriassic. It includes dinosaurs,pterosaurs, and crocodilians.

Arthropods Invertebrates with

segmented bodies and a hard(outer) exoskeleton. They formthe largest phylum (majordivision) in the animal kingdom,with well over a million livingspecies. Extinct arthropodsinclude trilobites andeurypterids; living ones includeinsects and spiders.

Artiodactyls (AR-tee-o-DAK-tilz)Hoofed mammals (ungulates)with an even number of toes.Pigs, camels, deer, giraffes, andcattle are living examples.

Australopithecines(os-TRAL-o-PITH-e-seen-z:“southern apes”) Extinct apelike hominids including the ancestors of humans.

Aves Birds. Some scientists restrictthe name Aves to modern birds(see also Neornithes), calling themost primitive birds Avialae.Birds probably evolved fromtheropod dinosaurs in the Late Jurassic.

Belemnites An extinct group ofsquidlike creatures. They werecharacterized by an internalchambered shell, enclosedentirely by soft, muscular tissue.

Bennettitales An extinct group of plants with palmlike foliage,and similar in appearance to theliving sago palms, or cycads.They produced star-shapedflowerlike reproductive structures.

Bilateral Having two sides. Thewings of a butterfly are one ofmany examples of bilateralsymmetry in the animal kingdom.

Bipedal Walking on the hindlimbsrather than on all fours.

Biostratigraphy The branch ofgeology that examines the fossilcontent of rock layers.

Biozone A division of geologicaltime identified by the presenceof particular species fossilized inrock layers.

Bivalves Aquatic mollusks, such as clams, that are enclosed by a hinged shell. The two halves of the shell are usually mirrorimages of each other.

Blastopore An opening in anembryo. In some organisms, the blastopore will become themouth or anus, in others, part of the digestive system.

Bovoids (boe-VOYD-z: “oxlike”)Artiodactyl hoofed mammalsincluding pigs, hippopotamuses,camels, pronghorns, deer,

B

giraffes, cattle, and their kin.Brachiopods Marine invertebrates

with a two-valved shell. They areclassified by whether or not thevalves are hinged. They evolvedin the Cambrian period but arenow a minor group.

Bryozoans Marine invertebratesthat grow in branching or fan-like colonies measuring a few inches across. They haveflourished since the Ordovicianperiod, in bothdeep and shallow waters.

Burgess Shale The site in British Columbia, Canada, where an important discovery of Middle Cambrian fossilsoccurred. Among the 130 speciesidentified are sponges, jellyfish,worms, and arthropods.

Caecilians Burrowing, wormlikeamphibians, which have poorlydeveloped eyes and no limbs.

Calcareous Any rock containingcalcium carbonate.

Calcified To be converted tocalcium carbonate, such as when bones or shells haveformed chalk, limestone, or marble.

Calcite A widely distributed rock-forming mineral, commonin the shells of invertebrates. It is the chief constituent oflimestone.

Cambrian The first period of thePaleozoic era, about 542–488.3million years ago. This was whenmost of the main invertebrategroups appeared in the fossilrecord.

Carbonate A substance containingcarbon with calcium ormagnesium, for examplelimestone or dolomite.

Carboniferous The fifth period of the Paleozoic era, about359.2–299 million years ago. The period is divided in NorthAmerica into the Mississippian(359–318 MYA) andPennsylvanian (318–299 MYA). It was during the Pennsylvaniansubperiod that extensive forestscovered the land, and werecolonized by insects and four-legged vertebrates includingamphibious tetrapods, and thefirst reptiles and synapsids.

Carbonized Describing organicmatter that has decomposedunder water or sediment, leavinga carbon residue. The residuepreserves many features ofplants, insects, and fish.

Carinates A group of birds withdeeply keeled breastbones.

Carnassials The bladelike cheek

C

Acanthodians (ae-KAN-tho-DEE-anz: “spiny sharks”) Extinct fishthat had fins supported bystrong, immovable spines. Theirheyday was the Devonian period.

Acetabulum The hip socket. Actinopterygians (ak-tin-op-ter-IG-

ee-nz) The ray-finned fish, amajor group of osteichthyans(bony fishes).

Adaptations The ways in whichorganisms evolve in response to their environment.

Aerofoil The curved suface of awing that aids flight by creatingan upward force.

Agnathans (ag-NAY-thanz: “withoutjaws”) A class of primitivevertebrates, the “jawless fish,”that flourished mainly in EarlyPaleozoic times. They includeextinct groups and the livinghagfish and lampreys.

Algae Primitive plants and plant-like organisms that grow in wet conditions.Cyanobacteria (“blue-greenalgae”) were among the firstorganisms to evolve and helpedto create the oxygen-richatmosphere essential for other lifeforms.

Allosaurs (AL-o-SORE-z: “strangelizards”) Big, meat-eatingdinosaurs – a group of ratherprimitive tetanuran theropods.

Amber The fossil form of the stickyresin produced by trees. Perfectlypreserved insects and otherorganisms have been foundfossilized in amber.

Ammonites An extinct group ofcephalopods that teemed inMesozoic seas. They had a coiled,chambered shell.

Amniotes Tetrapod vertebrateswhose young develop within aspecial protective membranecalled the amnion. Amniotesinclude reptiles, birds, and mammals.

Amphibians Cold-bloodedtetrapod vertebrates whoseyoung use gills to breathe during the early stages of life.Living amphibians include frogs, newts, and salamanders,whose ancestors originated in the Carboniferous period.

Amphibious Inhabiting both water and land. Crocodiles andotters are amphibious (but theyare not amphibians).

Anapsids A group of primitivereptiles with no skull opening

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GLOSSARY

teeth of carnivorans, designed to slice meat into pieces.

Carnivora A group of sharp-toothed, meat-eating mammals,including cats, dogs, bears, andtheir relatives and ancestors.People often call other meat-eating animals carnivores, too.

Carnosaurs Large carnivorousdinosaurs with big skulls andteeth. All such theropods wereonce called carnosaurs. Thename is now used only forAllosaurus and its relatives.

Cartilaginous Having a skeleton of cartilage (a firm but flexiblesubstance) rather than bone.

Catarrhines Primates with down-pointing nostrils that are closetogether, for example monkeys,apes, and humans.

Caudal Of, or relating to, a tail.Cenozoic The era that covers the

last 65.5 million years. It is subdivided into the Paleogeneperiod (65.5–23 million years ago)and Neogene period (23 millionyears to the present). See alsoTertiary; Quaternary

Cephalopods Marine molluskswith big eyes and a well-developed head surrounded by aring of tentacles. Examplesinclude ammonites, belemnites,octopuses, squid, and cuttlefish.

Ceratopsians (ser-a-TOP-see-anz:“horned faces”) Bipedal andquadrupedal, plant-eating,ornithischian dinosaurs with adeep beak and bony frill at theback of the skull. They includethe horned dinosaurs.

Ceratosaurs (se-RAT-o-SORE-z orSER-a-to-SORE-z: “hornedlizards”) One of the twoproposed major groups of theropods.

Cetaceans (se-TAE-see-anz:“whales”) Marine mammals with a streamlined, fishlike body and limbs evolved asflippers. They include dolphins,whales, and porpoises.

Chelonians (ke-LO-nee-nz:“tortoises”) Broad-bodiedreptiles, protected by a rooflikeshell. They comprise turtles,tortoises, and their ancestors.

Chimaeras Cartilaginous fishcharacterized by long, taperingtail fins.

Chondrichthyans (kon-DRIK-thee-anz: “cartilage fish”) Sharks,chimaeras, and kin: fish with acartilaginous skeleton and jaws.

Chondrosteans (kon-DROS-tee-anz: “cartilage-boned”) Primitiveray-finned fish including thesturgeons and paddlefish.

Chordates Animals that have anotochord.

Chronological Arranged in orderof occurrence.

Clade A group of organisms (suchas dinosaurs) sharing anatomicalfeatures derived from the sameancestor.

Cladistic (kla-DIS-tik) Describing a method of classifying plantsand animals by grouping themin clades.

Cladogram (KLAD-o-gram) A branching diagram showingthe relationships of differentclades.

Class In the Linnaean system of classification, a group oforganisms containing one ormore related orders (sometimesgrouped in subclasses).Classesinclude Aves (birds), Reptilia(reptiles), and Mammalia(mammals).

Cold-blooded Depending uponthe heat from the sun for bodywarmth.

Continental drift The movementof continents across the surfaceof the Earth over time.

Cretaceous The last period of theMesozoic era, about 145.5–65.5million years ago.

Crinoids (sea lilies) Plant-shapedechinoderms that are either free-floating or anchored to thesea-floor by long stalks. Theyform an important fossil groupin Paleozoic rocks.

Crustaceans A large class ofarthropods named after the hardcarapace, or “crust,” that encasestheir bodies. Living examplesinclude crabs, shrimp, andwoodlice.

Cycads (sie-kadz) Palmlike, seed-bearing plants that are topped bya crown of fernlike leaves. Theymay be short and shrublike, orgrow as high as 65 ft (20 m).

Cynodonts (SIE-no-dontz: “dogteeth”) Extinct, doglike synapsidsthat included the ancestors ofmammals.

Descendant A living thing that isdescended from another.

Devonian period The fourthperiod of the Paleozoic era,about 416–359.2 million yearsago. In Devonian times, tetrapods(four-legged vertebrates) wereevolving from fish.

Diapsids (die-AP-sidz) A majorgroup of reptiles, typically withtwo holes in the skull behindeach eye. Diapsids include lizards,crocodiles, dinosaurs, and birds.Their ancestors originated inLate Carboniferous times.

Dicynodonts (die-SIE-no-DONT-z:“two dog teeth”) Extinct, four-legged therapsids with long,downward-pointing tusks.

D

Digit A finger, thumb, or toe.Dinosaurs (DIE-no-sore-z:

“terrible lizards”) A great group of advanced archosaurswith erect limbs.

Diplodocids (di-PLOH-do-sidz:“double beams”) A family ofhuge saurischian dinosaurs: long-necked, long-tailed, plant-eatingsauropods. Diplodocids includedDiplodocus and Apatosaurus.

Diprotodonts (die-proe-toe-DON-tz: “two first teeth”) The largest of the extinct giantmarsupials, diprotodonts wererhinoceros-like creatures, withhuge rodent-like incisor teethand massive skulls. These forest-dwellers browsed on low-growingtrees and shrubs.

Disconformity A break betweenparallel rock layers representinga time when no sediment wasdeposited. It indicates anenvironmental change in theaffected area.

Diversify To become more varied.In evolution, for example, whena few species evolve into manyspecies, which are adapted todifferent environments.

DNA Deoxyribonucleic acid,whose molecules carry geneticinstructions from one generationto the next. (See Genes.)The complex double-helixstructure of DNA was discovered in the 1950s.

Domesticated Bred to be tame, as with cows, sheep, and dogs,which now live alongside human beings.

Dominant and recessive Termsdescribing inheritedcharacteristics that depend onthe type of gene inherited fromeach parent. For example, inhumans brown-eye genes aredominant, while blue-eye genesare recessive.

Dromaeosaurids (DROH-mee-o-SORE-idz: “running lizards”)Bird-like, bipedal, carnivorousdinosaurs. Most grew no longer than 6 ft (1.8 m).Dromaeosaurids lived in all northern continents.

Echinoderms (i-KIE-no-dermz: “sea urchin skins”) Marineinvertebrates with a hard, chalky skeleton and a five-rayedsymmetry. They evolved during the Cambrian period and include starfish, sea lilies,sea cucumbers, and sea urchins.

Echinoids (I-KIE-noydz) Seaurchins – echinoderms with arigid, globular (rounded) outerskeleton of spiny plates, pierced

E

by narrow tube feet for walking.Ecosystem A natural system that

is made up of a community ofliving organisms and theenvironment in which they live.

Ectotherm A cold-blooded animal. Ediacarans Fossil organisms

named after those found in the Ediacaran Hills of SouthAustralia. These complex, soft-bodied animals were foundin rocks that were about 560million years old.

Elasmobranchii (ee-LAZ-mo-BRAN-kee: “metal plate gills”) The main group ofchondrichthyan fish, includingthe sharks, skates, and rays.

Elasmosaur (ee-LAZ-mo-SORE:“metal plate lizard”) A long-necked type of plesiosaur: abulky, Mesozoic marine reptilewith paddle-like limbs.

Elytra The hard outer wingcases ofbeetles and some other insects.

Embryo An animal or plant in its early stage of developmentfrom a fertilized egg or seed.

Eocene The second epoch of theTertiary period, about 55.8–33.9million years ago. Hoofedmammals, whales, and primatesdiversified in this epoch.

Eon The longest unit of geologicaltime. From oldest to youngest,the four eons are called Hadean, Archean (Archaean),Proterozoic, and Phanerozoic.The Phanerozoic eon comprisesthe Paleozoic, Mesozoic, andCenozoic eras.

Epoch An interval of geologicaltime that is longer than an age and shorter than a period.

Era A unit of geological time that ranks below an eon.

Erosion The wearing away of thesurface of the Earth by naturalforces, such as wind and movingice and water.

Eukaryotes (yoo-KARRY-oatz:“having a true nucleus”) All organisms made of cells witha nucleus. Eukaryotes evolvedfrom prokaryotes at least 800million years ago.

Eurypterids (yoo-rip-ter-idz: “wide wings”) Sea scorpions,living in salt- and freshwater inthe Paleozoic era. Some grewmore than 6 ft 6 in (2 m) long.

Evolution The process by whichone species gives rise to another.It occurs because individualorganisms pass on mutations(chance changes in genescontrolling such things as body size, shape, and color).Individuals with beneficialmutations pass these on, so their kind multiplies. In this way new species eventually arise.

Excavation Digging out and

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removing fossils or othersubstances from the ground.

Exoskeleton An external skeleton.External skeletons appearedamong various marineinvertebrates in Cambrian times.

Extinction The dying out of aplant or animal species. This maybe caused by increasedcompetition for resources, orunfavorable changes in theenvironment, such as alterationsin climate or sea level or anasteroid striking the Earth.

Fenestra A small hole, or opening,in a bone.

Flagellum A long, whiplikeappendage found on somemicroscopic organisms.

Foraminiferans Minute aquaticorganisms with a single or multi-chambered shell. Their fossilsare important indicators of theages of some rocks.

Fossil The remains of a prehistoricorganism preserved in theEarth’s crust.

Fossilization Any fossil-formingprocess. As organic substancesdecay, they may be reduced to acarbon residue, a process calledcarbonization. Bones and shellsmay be impregnated by mineral-bearing solutions, in a processknown as permineralization.Original hard parts may bedissolved away and entirelyreplaced by a mineral substance,in a process known as petrifaction.

Gastropods The largest, mostsuccessful class of mollusks. Their internal organs aregenerally carried in a spiral shell, they have a head with eyes and mouth, and a flattenedfoot for crawling. Livingmembers of the class includesnails, cowries, and limpets.

Genes Microscopic units of cellsthat control inheritedcharacteristics. They are passedon from parents to their young.

Genets Catlike mammals of thegenus Genetta, characterized byspotted fur and a long, bushytail. Native to Africa andsouthern Europe.

Genus (plural: genera) A group of related organismsranked between the levels offamily and species.

Geological Concerning geology,the scientific study of thecomposition, structure, andorigins of the Earth’s rocks.

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F

Gharial A large Indian reptilerelated to crocodiles. It has along, very narrow snout.

Giraffids (ji-RAF-idz: “giraffes”) A family of hoofed, plant-eatingmammals – artiodactyls with longnecks and forelegs.

Girdles (hip and shoulder girdles)The hip bones and shoulderbones of tetrapod vertebrates,forming structures that supportthe limbs.

Glossopteris (glos-OP-ter-is:“tongue fern”) A Permian seed-fern found on all southerncontinents when they weregrouped as Gondwana.

Glyptodonts (GLIP-to-dontz:“carved teeth”) Large, armadillo-like mammals from SouthAmerica with hard, thick, bonyshells; now extinct.

Gondwana The vast southernsupercontinent that includedSouth America, Africa,Antarctica, Australia, and India.Gondwana persisted fromPrecambrian times until theJurassic period, when these lands began to move apart.

Graptolites (GRAP-to-lietz:“writing on the rocks”) Extinct,tiny, colonial marine animalswhose branching tubularexoskeletons left impressions inshale. These fossils help scientistsdate others from the Ordovicianand Silurian periods.

Habitat The natural home of an organism.

Hadean The first eon of thegeological time scale, about4.6–3.8 billion years ago.

Hadrosaurs (HAD-ro-SORE-z:“bulky lizards”) The duck-billeddinosaurs – large, bipedal/quadrupedal Late Cretaceousornithopods that used theirducklike beaks for browsing.

Hagfish A living kind of jawlessfish (agnathan).

Hallux The innermost digit (“big toe”) of the hindfoot of tetrapod vertebrates.

Herbivore Any animal that eatsonly plants. The teeth, stomachand digestive system of herbivoresare adapted to breaking downfibrous plant material.

Hesperornithiformes(HES-per-OR-nith-i-form-eez:“western bird forms”) Toothed,flightless, foot-propelled divingbirds of Late Cretaceous times.

Holocene The most recent epochof geological history, lasting from10,000 years ago to the present.

Hominids The group of primatesthat includes humans and their

H

living and extinct relatives. Hybrid The offspring of two

species.

Iapetus Ocean The precursor ofthe Atlantic Ocean, between theancient continents of Laurentia(mainly North America) andBaltica (northern Europe). The ocean closed during theOrdovician period.

Ichthyosaurs (IK-thi-o-SORE-z:“fish lizards”) Fishlike Mesozoicmarine reptiles that resembledmodern dolphins.

Igneous rocks Rocks formed from magma: molten matteroriginating deep down in theEarth.

Iguanodontians (i-GWAHN-o-dont-i-anz: “Iguana teeth”)Large, bipedal/quadrupedal,plant-eating dinosaurs:ornithopods that flourished in the Early Cretaceous.

Ilium One of the three (paired) hip bones.

Inherited Passed down throughthe generations.

Insectivore Any insect-eatingorganism, including certainplants, but especially the groupof mammals including moles,shrews, and hedgehogs.

Invertebrates Animals withoutbackbones.

Ischium One of the three (paired) hip bones.

Jerboa A small desert rodent withlong hindlegs.

Jurassic The middle period of theMesozoic era, about 199.6–145.5million years ago. At this timedinosaurs dominated the land,the first birds evolved, andmammals began to diversify.

Juvenile A young or immatureindividual.

Kin Family – individuals that aregenetically related.

Lamprey A living type of jawlessfish, with a sucker mouth andhorny teeth.

Lancelets Small, invertebrate, fish-like chordates that burythemselves in the sand.

Lepospondyls (LEP-o-SPON-dilz)Small, salamander-like and

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snakelike amphibious andaquatic tetrapods that flourished in Carboniferous and Permian times.

Lissamphibians (LISS-am-FIB-ee-anz) Living amphibians and theirclosest ancestors. Lissamphibiansinclude caecilians, frogs, andsalamanders.

Lophophorates (LOF-o-FOR-aitz)Invertebrate animals that possessa lophophore, a fan of tentaclesaround the mouth. Thelophophorates include thebryozoans and brachiopods.

Lungfish A group of lobe-finned,bony fish that evolved in theDevonian. They have both gillsand lungs and can breathe inwater and air.

Mammaliaforms Mammals’ closest,extinct, relatives, differing frommammals only in smallanatomical details.

Mammals Warm-blooded, hairyvertebrates that secrete milk andsuckle their young. Livingmammals range from tiny shrewsto the blue whale, the largestcreature ever, and between themoccupy a great variety of habitats.Mammals originated in Triassic times.

Maniraptorans (man-i-RAP-tor-anz:“grasping hands”) Predatory dinosaurs includingbirds. They were advancedtetanuran theropods with long arms and hands.

Maneuverability An ability toperform complex movementswith ease and agility.

Marginocephalians(mar-JIN-o-se-FAL-ee-anz:“bordered heads”) Ornithischiandinosaurs with a skull ridge orshelf – the pachycephalosaursand ceratopsians.

Marsupials Mammals that givebirth to small, undevelopedyoung that grow and mature in a skin pouch on the mother’sstomach. Living examplesinclude kangaroos and wallabies.Marsupials survive only inAustralasia and the Americas.

Mastodons (MAS-to-dons) An extinct group of largemammals with trunks, tusks, and thick hair. They were related to the elephants.

Megalosaurs (MEG-a-lo-SORE-z:“great lizards”) A mixed group of large carnivorous dinosaurs.They were primitive tetanurantheropods less advanced than the carnosaurs.

Mesoderm The middle layer ofcells in an embryo. In vertebrates

M

363

GLOSSARY

the mesoderm develops intomuscles, bones, the circulatorysystem, and various internalorgans and glands.

Mesosaurs (MEZ-o-SORE-z:“intermediate lizards”) Primitive, somewhat lizardlikeaquatic reptiles of Permian times.They swam by waggling theirflattened tails.

Mesozoic The “middle life” era,about 250–65 million years ago,containing the Triassic, Jurassic,and Cretaceous periods. This was the Age of theDinosaurs – their extinction ismarked by the end of the era.

Metamorphosis Change of shape,as when the young of somecreatures take on adult form, forinstance a tadpole becomes a froglet, and a caterpillarbecomes a pupa and then a winged butterfly.

Metatarsals Foot bones betweenthe ankle and toes.

Metazoans Many-celled animals(this applies to the vast majorityof animals).

Microfossils Fossils too small to be seen with the naked eye. They include the shells ofsome microscopic, single-celledorganisms, plant spores, pollengrains, and the bony scales ofcertain fish.

Miocene The fourth epoch of thePaleogene period, about 23–5.3million years ago.

Mitochondrion A structure withina cell containing enzymes(special proteins) for energyproduction and respiration.

Mollusks A great group ofinvertebrates including bivalves,gastropods, and cephalopods,many important as marine fossils.

Monotremes Primitive, egg-layingmammals that evolved by theMid-Cretaceous. Only theplatypus and echidnas (spinyanteaters) survive.

Mosasaurs (MOZE-a-SORE-z)Large, Cretaceous marinereptiles – long-jawed aquaticlizards with slender bodies andflipperlike limbs. They werefierce predators.

Multituberculates Small, rodent-like mammals of Late Jurassic toEarly Cenozoic times. Many weremouse-sized, the largest as big asa beaver.

Natural selection The natural“weeding out” of weakerindividuals that guides evolution.As generations of individualsmutate, those whose mutationsare favorable (making them

N

stronger, faster, etc.) survive ingreater numbers to reproduceand pass on their mutations tothe next generation.

Nautiloids (NOR-til-OY-dz) A type of cephalopod living in a straight or coiled, chamberedshell. Nautiloids swim bysquirting water out of the bodycavity. They reached their peakin the Ordovician and Silurianbut only a single genus survives:the pearly nautilus of the Pacificand Indian oceans.

Neanderthal (nee-AN-der-taal) An extinct species of hominidthat is closely related to our ownspecies.

Nematodes Parasitic and free-living worms with a slender,unsegmented cylindrical shape;also called roundworms.

Neoceratopsians (NEE-o-sera-TOP-see-anz: “new horned faces”)Small to large, mainly four-legged ceratopsians, many with huge, horned heads.

Neogene The period of geologicalhistory covering the last 23 million years, divided into theMiocene, Pliocene, Pleistocene,and Holocene epochs. See alsoTertiary; Quaternary

Neornithes (nee-ORN-ith-eez:“new birds”) Birds of the moderntype, with a toothless beak, anddistinctive bones not found inearlier forms.

Neural Relating to the nerves or central nervous system.

Niche A set of environmentalconditions that are uniquely well suited to the survival of a particular species.

Nocturnal Relating to the night.Nocturnal creatures are activeduring the hours of darkness and sleep during daylight.

Notochord A flexible internal rodstiffening the body of chordates.It forms the basis of thebackbone in vertebrate animals.

Nummulites Foraminiferans withdisc-shaped and lens-shapedshells; plentiful in someCenozoic rocks.

Olfactory Relating to the sense of smell.

Oligocene The third epoch of thePaleogene period, about 33.9–23million years ago. Many of themodern animal familiesflourished, but with species thatare now extinct.

Onychophorans (ON-ik-o-FOR-anz)Long, wormlike invertebrateswith many stumpy limbs. Theyare closely related to arthropods.The earliest lived in the

O

Cambrian period.Ordovician The second period

of the Paleozoic era, about488.3–443.7 million years ago. Allcreatures known from this timelived in water.

Organelle A specialized structurewithin a cell.

Ornithischians (or-ni-THIS-kee-anz: “bird hips”) One of the twomajor dinosaur groups (see alsoSaurischians). The pelvis ofornithischians is similar to thepelivis of birds.

Ornithodirans (or-ni-thoe-DIRE-anz: “bird necks”) The group of archosaurs that includesdinosaurs, pterosaurs, and birds.

Ornithopods (or-ni-thoe-POD-z:“bird feet”) A group of large andsmall ornithischian dinosaurs:plant-eaters that walked on theirlong hindlimbs or at leasthurried along on them.

Ossicle A small bone or bonelikebody part, for instance the calciteplates of echinoderms.

Osteichthyans (OS-tee-IK-thi-anz:“bony fish”) Fish with a bony not cartilaginous skeleton. They include the ray-finnedactinopterygians and lobe-finnedsarcopterygians.

Osteostracans (OS-tee-o-STRAK-anz: “bone shields”) Early jawlessfish whose head and gills wereenclosed in a heavy bony shield.

Overburden Sediment or othermaterial that must be removed to reach an underlying deposit of fossils or minerals.

Oviraptorids (OH-vi-RAP-tor-idz:“egg stealers”) A family of long-legged, beaked, birdlikemaniraptoran theropod dinosaurs.

Pachycephalosaurs (pak-i-SEF-a-lo-SORE-z: “thick-headed lizards”)Bipedal ornithischian dinosaurs:marginocephalians withimmensely thick skulls.

Paleobotany The study of fossilplants. This is useful inunderstanding ancient ecology,and can also help scientists to match the dates of different rock samples.

Paleocene The first epoch of thePaleogene period, about65.5–55.8 million years ago.Large mammals appeared during this epoch.

Paleoecology The study of therelationships between fossilorganisms and their ancientenvironments. Comparisons areoften made with modernecosystems.

Paleogene The first period of the Cenozoic era, about

P

65.5–23 million years ago,divided into the Paleocene,Eocene, and Oligocene epochs.See also Tertiary

Paleontology The scientific studyof fossil plants and animals.

Paleozoic (“ancient life”) Thegeological era from 542–251million years ago, comprising theCambrian, Ordovician, Silurian,Devonian, Carboniferous, andPermian periods.

Palpebral A bony eyelid, as seen in some ankylosaurs.

Palynology The study ofmicroscopic pollen and sporesand their spread. Palynology is a branch of paleoecology andpaleobotany.

Pampas Treeless, grass-coveredplains.

Pangea (pan-JEE-a) The supercontinent formed atthe end of the Paleozoic era.Pangea consisted of all the majorcontinental blocks and stretchedfrom pole to pole.

Parareptiles (PAR-a-REP-tile-z:“near/beside reptiles”) Primitivereptiles, including the mesosaurs.Some people have used the termto include all the reptiles knownas anapsids.

Pareiasaurs (par-EE-a-SORE-z) A group of early reptilescharacterized by massive bodiesand strong limbs. Their skullshad many bony protuberances.

Peccary A piglike type of hoofedmammal native to the Americas.

Pelvis The hip girdle. (See Girdles.)Period The unit of geological time

between era and epoch. Periodsare an era’s main subdivisions.

Perissodactyls (per-IS-o-DAK-tilz)The “odd-toed” hoofed mammals,including horses, rhinoceroses,tapirs, their ancestors, andvarious extinct forms.

Permafrost Permanently frozenground. The surface thaws in thehigher temperatures of summer,but water cannot drain awaythrough the frozen subsurface.

Permian The last period of thePaleozoic era, about 299–251million years ago. The end of the Permian saw a worldwidemass extinction of life-forms.

Phalanges (singular: phalanx) Toe and finger bones.

Phanerozoic (“visible life”) Thecurrent eon of geological time,spanning the last 540 millionyears, characterized by theevolution of plants and animals.The Phanerozoic comprises thePaleozoic, Mesozoic, andCenozoic eras.

Phragmocone (FRAG-mo-kone)The cone-shaped internal shellof belemnites. It is divided intochambers.

364

REFERENCE SECTION

Phylum A major subdivision of the animal kingdom, comprisinga class or classes.

Phytosaurs (FIE-to-SORE-z)Heavily armored, semiaquaticTriassic archosaurs: reptilesresembling modern crocodilesand with similar habits.

Pikas Small, short-eared relativesof hares and rabbits. They live inrocky, mountainous parts of Asiaand North America.

Placentals Mammals whoseunborn young are nourished bya special organ called a placenta.Placental mammals havereplaced marsupials in mostparts of the world.

Placoderms (PLAK-o-dermz:“plated skins”) A class of jawedfish, protected by armorlikeplates. They flourished inDevonian times.

Placodonts (PLAK-o-dontz: “plated teeth”) Aquatic reptilesof the Triassic period. Some“rowed” with paddle-shapedlimbs, others swam with webbeddigits and by waggling their tails.

Planarian A type of flatworm oftenfound in freshwater.

Plastid In a plant cell, a structurecontaining pigments, food, orother substances.

Platyhelminthes Flat-bodiedworms, also called flatworms.

Pleistocene The third epoch of theNeogene period, 1.81 million to10,000 years ago. It was markedby a series of ice ages (really oneice age with cold and warmphases).

Plesiosaurs (PLEE-SEE-o-SORE-z)Large Mesozoic marine reptilesthat that swam with flipper-shaped limbs. Many were long-necked, reaching lengths of 10–40 ft (3–12 m).

Pliocene The second epoch of theNeogene period, about 5.3–1.81million years ago. The firstspecies of the genus Homoappeared in this epoch.

Precambrian The great span oftime from the Earth’s formationto the Cambrian Period.Scientists divide the Precambrianinto three eons. (See Eon.)

Predator Any animal or plant thatpreys on animals for food.

Prehensile Designed to graspsomething by wrapping aroundit. For example, South Americanmonkeys have prehensile tails.

Preservation Keeping something,for example a fossil, free fromharm or decay.

Primates The group of mammalsthat includes lemurs, monkeys,apes, humans, and theirancestors.

Primitive At an early stage ofevolution or development.

Proboscideans Elephants and theirextinct ancestors and relatives –mostly large mammals possessinga long flexible trunk.

Prokaryotes (pro-KARRY-oatz:“before a true nucleus”) Tiny,primitive organisms without a cell nucleus. They comprise the bacteria and archaea.

Pronghorns Antelope-like NorthAmerican mammals that shedtheir horns’ outer covering. Only one species survives today.

Prosauropods Early plant-eatingsaurischian dinosaurs includingbig four-legged forms resemblingthe sauropods that replacedthem. Prosauropods lived fromLate Triassic to Early Jurassictimes.

Proterozoic The third eon of thegeological timescale, from about2.5 billion to 540 million yearsago. The first eukaryotesappeared in this time.

Protozoans A great and variedgroup of tiny one-celledorganisms, for example theforaminiferans.

Psittacosaurs (SIT-a-ko-SORE-z or si-TAK-o-SORE-z: “parrotlizards”) Bipedal, plant-eatingCretaceous dinosaurs with a deepbeak somewhat like a parrot’s.They were ceratopsianornithischians related to the later neoceratopsians (horneddinosaurs).

Pterodactyloids (TER-o-DAK-tee-loidz) Short-tailed pterosaursthat replaced long-tailed earlyforms.

Pterosaurs (TER-o-SORE-z: “wingedlizards”) Skin-winged, Mesozoicflying reptiles – archosaurs relatedto the dinosaurs.

Pubis One of the three (paired) hip bones.

Pygidium The tail of a trilobite or certain other kinds of

invertebrate.Pygostyle The short tailbone of a

bird, formed of fused vertebrae.

Quadrupedal Walking on all fours.Quaternary In one dating scheme,

the second period of theCenozoic era, covering the last1.8 million years. See also Neogene

Reconstruction Rebuilding, forinstance reassembling scatteredfossil bones to reconstruct theskeleton of an extinct animal.

Reptiles Lizards, snakes, turtles,crocodiles, dinosaurs, and theirextinct and living relatives.

R

Q

Living reptiles are cold-blooded,scaly vertebrates that reproduceby laying eggs or giving birth on land.

Reptiliomorphs Small, lizardliketetrapods that gave rise to truereptiles.

Rhinocerotidae (“nose horns”) A family of plant-eating hoofedmammals related to tapirs andhorses. Living rhinoceroses arelarge, thick-skinned quadrupedswith a horn or two horns ontheir snouts.

Rhomboidal Having the shape of a rhombus (a sloping square).

Ribosome A type of particlemaking proteins in a cell.

Rodents A group of smallmammals including mice, rats,squirrels, porcupines, and theirextinct ancestors. Rodents havesharp front teeth used forgnawing grains, nuts, and seeds.

Sacrum Fused vertebrae that arejoined to the pelvis.

Sarcopterygians (SAR-KOP-ter-ig-ee-anz: “flesh fins”) The lobe-finned or fleshy-finned bony fish,comprising lungfish, coelacanths,and so-called rhipidistiansincluding the ancestors of all four-legged vertebrates.

Saurischians (sore-IS-kee-anz:“lizard hips”) One of the twomajor dinosaur groups (see alsoOrnithischians). The pelvis ofmost saurischians is similar tothat of lizards.

Sauropodomorphs (sore-o-POD-o-morfz: “lizard-foot forms”)Mostly large to immense, four-legged, long-necked, plant-eatingsaurischian dinosaurs. Theycomprised the prosauropods and sauropods.

Sauropods (SORE-o-podz: “lizardfeet”) Huge, plant-eating,quadrupedal saurischiandinosaurs, including the largest-ever land animals. They livedthrough most of Mesozoic time.

Sauropterygians (SORE-op-te-RIG-ee-anz) Mesozoic marine reptilesincluding the nothosaurs,placodonts, and plesiosaurs.

Scutes Bony plates with a hornycovering set in the skin of certainreptiles to protect them from the teeth and claws of enemies.

Sediment Material deposited bywind, water, or ice.

Silurian The third period of thePaleozoic era, about 443.7–416million years ago. It was namedafter the Silures, an ancient tribein Wales.

Sirenians (sigh-REE-nee-anz)Large plant-eating aquatic

S

mammals. Sea cows and dugongsare the only living examples.

Skull The head’s bony frameworkthat protects the brain, eyes, ears,and nasal passages.

Species In the classification ofliving things, the level below agenus. Individuals in a speciescan breed with each other toproduce fertile young.

Stegosaurs (STEG-o-SORE-z:“plated/roof lizards”) Four-legged ornithischian dinosaurs –plant-eaters with two tall rows ofbony plates and/or spinesrunning down the neck, back,and tail.

Stereoscopic A type of eyesight or photography where both eyesor two lenses slightly apart focuson an object to give a three-dimensional effect.

Stratigraphy The study of layers of sedimentary rock (strata).

Stromatolite A mound made ofblue-green algae interlaid withlime “mats.” Stromatolitesabounded in intertidal waters inPrecambrian times, before algae-eating sea creatures appeared.Fossil stromatolites are earlyevidence of widespread life.

Supercontinent A prehistoriclandmass containing two or more major continental plates.Examples include Gondwana and Pangea.

Symbiosis The living together ofindividuals of different speciesthat benefit from thisarrangement.

Synapsids The group of tetrapodvertebrates that includes theextinct pelycosaurs andtherapsids, and the therapsids’descendants – mammals.

Tardigrades Tiny invertebrateswhose bodies are composed offour segments, each bearing apair of unjointed limbs. They live in damp moss, on floweringplants, in sand, in freshwater,and in the sea.

Tarsiers Small nocturnal primateswith big eyes and ears, long tails,and long hindlegs for leapingfrom tree to tree. They live inSoutheast Asia.

Teleosts A great group of the ray-finned bony fish(actinopterygians). Most living fish are teleosts.

Temnospondyls (TEM-no-SPON-dilz: “cut vertebrae”) A group of early tetrapods includingweak-limbed aquatic fish-eatersbut also sturdier forms livingmainly on land.

Tertiary In one dating scheme, the

T

365

GLOSSARY

first period of the Cenozoic era,about 65–1.8 million years ago.See also Paleogene; Neogene.

Tetanurans (TET-a-NYOOR-anz:“stiff tails”) The major group oftheropod dinosaurs.

Tetrapods (TETRA-podz: “fourfeet”) Four-legged vertebratesand those two-legged andlimbless vertebrates descendedfrom them.

Thecodonts (THEEK-o-DONT-z:“socket-teeth”) A mixed group of archosaurs including variousextinct forms, among them theancestors of dinosaurs,crocodilians, and pterosaurs.

Therapsids (ther-AP-sidz:“mammal arches”) Prehistoricsynapsids that includedcynodonts, the immediateancestors of mammals. Theylived from Early Permian to Mid-Jurassic times.

Theropods (THER-o-podz: “beastfeet”) The predatory dinosaurs,many armed with sharp teethand claws. They ranged fromhen-sized creatures to thecolossal tyrannosaurids.

Thylacines (THIE-la-seenz:“pouched”) Also calledTasmanian wolves, these werefoxlike marsupials. Until about10,000 years ago, they werefound on the mainland ofAustralia and New Guinea. The last known thylacine wascaptured in 1930 in Tasmania.

Thyreophorans (THIHR-ee-OFF-o-ranz: “shield bearers”) Four-legged, plant-eating dinosaurscomprising the armoredankylosaurs, plated stegosaurs,and their close relatives.

Titanosaurs (tie-TAN-o-SORE-z:“gigantic lizards”) Very large,four-legged, plant-eatingdinosaurs. The titanosaurs weresauropods and included perhapsthe largest land animals ever.

Topography The surface of theland, including its variations in height.

Trace fossils Traces left byprehistoric creatures. Theyinclude fossil burrows, footprints,eggs, droppings, bite marks, andfossil impressions of skin, hairand feathers.

Triassic The first period of theMesozoic era, about 251–199.6million years ago. Dinosaursemerged in the Triassic period.

Triconodonts (try-KON-o-dontz“three cone teeth”) An extinctgroup of primitive mammals,known across North America,and from Europe to China.

Trilobites (TRY-lo-bite-z: “threelobed”) Paleozoic marinearthropods with externalskeletons divided lengthwise

into three lobes. Variations intrilobite shapes and features arean accurate indicator of the ageof the sediments in which theyare found.

Tylopods (TIE-lo-podz: “paddedfeet”) Artiodactyl (even-toed),hoofed mammals includingcamels, the llama, alpaca,guanaco, and vicuña, and their extinct relatives.

Tyrannosaurids (ti-RAN-o-SORE-idz: “tyrant lizards”) A family of huge, bipedal, carnivorousdinosaurs: tetanuran theropodswith large heads, short arms, two-fingered hands, and massivehindlimbs. They flourished in Late Cretaceous NorthAmerica and Asia.

Ungulates Hoofed mammals.Unspecialized Not specialized –

not adapted, or set apart, for a specific purpose.

Vendian The former name of thelast Precambrian period of Earth history, now called the Ediacaran, about 630–542million years ago. Many-celledEdiacaran-type creatures appearedin the sea during this period.

Vertebrates Animals with aninternal bony or cartilaginousskeleton including a skull and abackbone made up of vertebrae

Vertebrae (singular: vertebra) Thelinked bones forming thebackbones of vertebrate animals.According to what part of abackbone they form, scientistsdescribe them as cervical (neck),dorsal (back), sacral (hip), andcaudal (tail) vertebrae.

Viscera Organs inside the bodycavity, for example the intestines,heart, and liver.

Warm-blooded Keeping bodytemperature at a constant level,often above or below that of thesurroundings.

Zone fossils (index fossils) Typesof fossil useful for determiningthe relative ages of rocks, andmatching the ages of rocks fromdifferent parts of the world.

Z

W

V

U

Acanthostega(a-kan-tho-STEEG-uh: “spiky roof”)

Aepycamelus(ee-pi-CAMEL-us: “high/lofty camel”)

Archaeopteryx(AHR-kee-OP-ter-iks: “ancient wing, feather”)

Australopithecus afarensis(AWS-tra-lo-pith-ee-cus:“southern ape from Afar”)

Caudipteryx (kaw-DIP-ter-iks or kaw-dip-TAYR-iks or KAW-dee-tayr-iks: “tail wing, feather”)

Cheirolepis (kyr-o-LEE-pis)Cladoselache (clade-o-su-LAK-e)Coelurosauravus

(seel-uro-sawr-AV-us)Compsognathus

(komp-SOG-na-thus or KOMP-sog-NAY-thus: “elegant jaw”)

Confuciusornis(con-foo-shush-OR-nis:“Confucius bird”)

Corythosaurus(ko-RITH-o-SAWR-us or KOR-i-tho-SAWR-us: “helmet lizard”)

Daeodon (DAY-oh-don) or Dinohyus (dine-oh-high-us)

Deinonychus (dine-on-EE-kus:“terrible claw”)

Diadectes (DIE-a-deck-teez)Dilophosaurus

(die-loph-UH-saw-rus: “double-crested lizard”)

Diplocaulus (dip-low-COR-luss)Dunkleosteus (dunk-lee-OS-tee-us)Echioceras (eck-ee-o-SAIR-us:

“spiky horn”)Edmontonia

(ed-mon-TOHN-ee-a: “from Edmonton”)

Elephas falconeri (ele-FAS ful-con-ear-ee)

Epigaulus (ep-ee-GAW-lus)Eryops (eer-EE-ops: “long face”)Estemmenosuchus

(es-tem-EE-nah-soo-kus)Euoplocephalus

(YOO-o-plo-SEF-a-lus: “well-armoured head”)

Herrerasaurus(he-RER-a-SAWR-us: “Herrera’s lizard”)

Hylonomus (hiy-LON-uh-mus:“forest mouse”)

Icaronycteris(ick-ah-row-NICK-ter-is)

Ichthyosaurus(ick-THEE-uh-SAWR-us: “fishlizard”)

Lepidotes (lep-ee-DOTE-eez)Lesothosaurus

(le-SOH-toh-SAWR-us: “Lesotho lizard”)

Macrauchenia (mack-row-CHEE-nee-uh: “big llama” or “big neck”)

Mastodonsaurus (MAS-toe-don-saw-rus: “mastodon lizard”)

Meganeura (meg-uh--NUR-us)Megatherium

(meg-uh-THEER-ee-um: “big beast”)

Metriorhynchus(met-ree-oh-RINK-us)

Miacis (my-ASS-is)Moeritherium

(moh-rih-THEER-ee-um)Morganucodon

(more-gan-OOH-kud-don)Oviraptor (OH-vi-RAP-tor:

“egg robber”)Pachycephalosaurus

(pak-i-SEF-a-lo-SAWR-us: “thick-headed lizard”)

Panderichthys (pan-der-ICK-theez)Paraceratherium

(para-sair-uh-THEER-ee-um)Phacops (fake-OPS)Phenacodus (fenn-ah-co-DUSS)Plateosaurus (PLAT-ee-o-SAWR-us

“broad, strong lizard”)Platybelodon

(plat-ee-BELL-uh-don)Plesiadapis (ples-ee-ah-DAP-is)Psittacosaurus (SIT-a-ko-SAWR-us

or si-TAK-o-SAWR-us: “parrot lizard”)

Pteranodon (TAIR-an-oh-don:“wing, no teeth”)

Pteraspis (TAIR-as-pis)Pterygotus (tear-ee-GOTE-us)Scelidosaurus (SKEL-i-do-SAWR-us:

“hindleg lizard”)Sinokannemeyeria

(SIEN-o-kanna-may-urh-ee-a)Styracosaurus

(STIHR-a-ko-SAWR-us or stie-RAK-o-SAWR-us:“spiked lizard”)

Suchomimus (SOOK-o-MIEM-us:“crocodile mimic”)

Tanystropheus(tan-ee-STROFE-ee-us: “stretched joints”)

Therizinosaurus(THER-i-ZIN-o-SAWR-us:“reaping lizard”)

Theropithecus(THAIR-oh-pith-ee-cus)

Thrinaxodon (thrin-AX-uh-don)Thylacosmilus

(thigh-LACK-uh-smy-lus)Tuojiangosaurus

(too-JUNG-uh-saw-rus)Uintatherium

(u-IN-tah-theer-ee-um: “Uintah beast”)

Zalambdalestes(za-LAMB-duh-less-tees)

ADDITIONALPRONUNCIATION GUIDE

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INDEXIn this index mainentries for each subjectare shown in bold type.Scientific names aregiven in italics.

Aaardvark (living) 245Abel, Roberto 110abelisaurids 110–11, 117Abel’s lizard seeabelisaurids

Abelisaurus 110Abrigo do Lagar Velho,Portugal 236

acanthodians 46, 284Acanthostega 56, 58, 59,286

Acara (living) 51Acer 304Acheulian culture 233actinopterygians 48, 288

adapids 226, 227adaptive radiation 354Aegyptopithecus 304Aepycamelus 266, 267aerial photographs 312aetosaurs 90, 91Afrovenator 112Agassiz, Douglas 344Age of the Amphibians341

age of coal 289Age of Cycads 296Age of the Dinosaurs102

Age of Fish 42Age of Reptiles 294ages 327agnathans 38Ailuropoda melanoleuca311

Alberta lizard seeAlbertosaurus

Albertosaurus 125Alectrosaurus 125algae (singular alga)284, 322, 324, 342see also blue-greenalgae, green algae

Alioramus 125allosaurs 104, 116Allosaurus 116, 118, 119,149jaws 116skeleton 102–3, 116

Alphadon 208alula 138, 139, 143Alvarez, Luis and Walter344

alvarezsaurids 142Alxasaurus 126amateur fossil collecting

see fossil hunting,amateur

amber 343Ambulocetus 274American pouchedmammals (marsupials)208–9, 324

Ameridelphia 208amids 37amino acids 344ammonites 10, 13, 30–1,338

ammonoids 286, 289,294

amniotes 35, 57, 66,68–9, 194

amniotic egg 35, 68amphibians 341cladogram 56–7see also under individual names

Amphicoelias 155amynodontids 256anagalids 242Anapsida 341anapsids 341anatomy of fossils 159,319, 320

ancestral ox see Bos primigenius

ancient wing see Archaeopteryx

Andrews, Roy Chapman317, 344

Andrew’s flesh-eater see Andrewsarchus

Andrewsarchus 272, 273Andrias 64angiosperms 298, 343ankylosaurids 174, 176–7

ankylosaurs 168, 174,175

annelids 23Anning, Mary 344Anomalocaris 15Antarctica 305, 307anteaters (living) 210antelopes 270, 271anthracosaurs 57, 66Anthropoidea 228anthropoids 228antilocaprids 271Antilophrax 251antlers 268antorbital fenestra 71anurognathids 94apatemyids 227Apatosaurus 149, 153,155, 349

apes 228, 230, 232aquatic animalsfossil timeline 279–311

aquatic plantsfossil timeline 282

arachnids 289Araripemys 74

Araucaria 343archaea 14Archaeocetes 273archaeocyathans 280Archaeopteris 286Archaeopteryx 138, 140–1,297

Archaeotherium 264Archaoethyris 68Archelon 74, 75Archimylacris 29Archonta 224archontans 195archosauromorphs 88,89, 94

archosaurs 71, 76, 88,90, 92, 294

Argentavis magnificens144

Argentinosaurus 117, 160argyrolagids 209Argyrolagus 209arm lizard see Brachiosaurus

armadillos (living) 210, 211

armor plates/armoreddinosaurs 160, 161,164, 168–9, 174–5,176–7fish 34, 36, 40–1, 340glyptodonts 211placodonts 80, 81reptiles 91, 92trilobites 24turtles 74

arsinoitheres 250Arsinoitherium 250arthrodires 41Arthropleura 68arthropods 15, 23, 28,345Cambrian period 280,281Silurian 284, 286

artiodactyls 195, 264,266, 267

asioryctitheres 213Aspidorhynchus 297asteroid impact 300, 301Asterophyllites 342Atlantic Ocean 25, 297atoms 328neutrons 328nucleus 328protons 328

Auca Mahuevo,Argentina 161

aurochs 270Australiapouched mammals(marsupials) 206–7, 324

australopithecines230–1, 352

Australopithecus 230–1,232aethiopicus 231

afarensis 230, 231, 351africanus 230, 347boisei 231, 316habilis (formerly Homohabilis) 231, 316robustus 231

aye-ayes 227azhdarchids 99

Bbabiesdinosaurs 182ichthyosaurs 86, 87mammoths 262psittacosaurs 187see also eggs, hatchlings

baboons 229bacteria 14, 15Bakh, A.N. 354Bakker, Robert 344Balaenoptera musculus 311

Bambiraptor 136, 137baphetids 56Baragwanathia 285Barapasaurus 152Barghoorn, Elso 344bark (Lepidodendron) 322

Barosaurus 149, 154, 155making replica displaymodel 149, 331

Barrande, Joachim 345Barsbold, Rinchen 345Barsboldia 345Barton, Otis 345Baryonyx 114, 115Basilosaurus 274, 275,303

bathysphere 345Batodon 224bats 222–3, 224–5, 302fish-eating 225fruit-eating 225horseshoe 225vampire 225

Bavarisaurus 120HMS Beagle 16, 347beaksbird 303dinosaurs 103, 166,175, 178, 182ornithomimids 122rhynchosaurs 89pterosaurs 95turtles 74

bear-dogs 220bears (living) 214, 220,221

beast teeth see theriodonts

beavers 239, 305Beebe, William 345beetles, water 28

Beipiao lizard see Beipiaosaurus

Beipiaosaurus 127Belemnitella 339belemnites 30–1, 296,339

Belemnoteuthis 31bennettitaleans 296, 343Bennettitales 297Betula (living) 298Betulites 298Bible 10bichirs (living) 48Bienosaurus 168Bienotherium 203big leg lizard see Barapasaurus

big lizard see Megalosaurus

big llama see Macrauchenia

bilaterians 32biogeography 233biomolecules 344biostratigraphy 326bipedal plant-eaters166–7

birch tree (living) 298Bird, Roland T. 345bird-hipped dinosaurs see ornithischians

birds 35, 88, 142–3,144–5, 341and dinosaurs 133, 348,350, 354ancestors of 103, 120,133bones/skull 139cladogram 138–9closest relatives 138evolution 139, 296, 297flightless 144, 302, 303, 305, 308, 310living 139, 144skeleton 138

Birkenia 284Bison priscus 270bivalves 339blue-green algae 282blowholes 275body fossils 12Bonaparte, José 110bonesand diseases 321and injuries 321dinosaurs 102, 156, 158replica 330see also dentary bone,palprebal bone, pteroid bone, rostral bone

bony club see tail club

bony fish 48, 50, 286,288

367

INDEX

classification 340cladograms 34, 36, 37

bony plates ankylosaurs 168, 174,175, 176placoderms 40, 41spiny sharks 47stegosaurs 168, 170,172, 173thyreophorans 168

bony scutes 92, 160, 164,168, 169, 211

bony “swords” 114boomerang head see Diplocaulus

boreholes 327Borhyaena 208borhyaenoids 208saber-toothed 208

borophagines 220Bos primigenius 270, 271bosses, on skin 73Bothriolepis 40, 340bovoids 266, 269, 270bowfins 37brachiopods 23, 282,284, 288, 290, 339

brachiosaurids 158, 160Brachiosaurus 153, 158–9

brachyopoids 61Branchiostoma 33brainaustralopithecines 230dinoceratans 241 dinosaurs 136, 159, 171Homo species 233, 235mammals 213

Branisella 229breedinggenetic manipulation311see also cross-breeding

Briggs, Derek 345brithopodids 198, 199Brongniart, Alexandre346

Brontops 254, 255Brontosaurus 149, 155brontotheres 243, 254–5

Brown, Barnum 345browsers 267bryozoans 290, 338Buckland, William 113,346

Buettneria 60Buffetaut, Eric 346Buffon, Georges-Louisde 346

buoyancy 50Burgess Shale 15, 280,281, 345, 357

burrowingdicynodonts 201rodents 238, 239

buttercups 309

Ccaecilians 64Caipora 229Calamites 288calcichordates 32calcium carbonate 312Callixylon 286camarasaurids 157Camarasaurus 156, 157Cambrian and evolution 23common index fossils327explosion 15, 280period 278, 280–1plants 342

camels 266–7camera lucida 319Camptonotus 178Camptosaurus 178, 179Candiacervus 240caniforms 220–1canine-like teeth 70, 71canine teeth dinosaurs 167 mammals 196, 198, 199,200, 201, 242, 272see also carnassials

Canis dirus 220, 221, 324

capitosaurs 61captorhinids 70carbon-14 (C-14)isotope327, 352

Carboniferous period 278, 288–9plants 322, 342, 343swamp forest 11, 62–3trees 69

Carcharocles 45carcharodontosaurids117

Carcharodontosaurus 117Caribbean Sea 306Carinatae 139carnassials 214, 216, 217, 218 see also canine teeth

Carnegie Quarry, Utahsee Douglass Quarry,Utah

carnivorans 214-15carnivores 202, 213, 219cladogram 194 see alsomeat-eaters, predators

carnosaurs 116–117Carnotaurus 110, 111carpoids 32cartilage 36, 44cartilaginous fish 34, 36,340

casting see under modelscatarrhines 228catfish 307cats 216–17(living) 214, 217see also saber-toothed

spruce 308Confucius bird see Confuciusornis

Confuciusornis 142, 143

confuciusornithids 138

conifers 322, 342ancestors of 286fossil timeline 288, 290, 294, 296, 298, 302, 304

conodonts 33, 283continental drift 290,357

continentalplates/continents,movement of 13, 323Cooksonia 284Cope, Edward Drinker346

copying fossils see reconstructing fossils

coral 338fossil timeline 288, 292,293, 294

Cordaites 289Coryphodon 213Corythosaurus 182, 183,299, 325

Cothurnocystis 32, 33crabs 286, 298craniates 33Cranioceras 269Crassatella 339Crassigyrinus 66, 67creodonts 215crests see head crestsCretaceouscommon index fossils327mass extinction 300–1period 278, 298–9plants 298–9, 322, 323,342

Crick, James 346, 357crinoids 285, 288, 296,339

crocodiles 90, 115crocodylomorphs 71,92–3, 294

crocodylotarsians 90, 91Cro-Magnons 236cross-breedinggrasses 311

crustaceans 298cryptoclidids 84cryptodires 75Crystal Palace, London332, 354

ctenophores 22CT-scan images 318, 321Currie, Philip J. 347Cuvier, Georges 347Cyathocrinites 339 cycads 322, 342fossil timeline 288, 290,294, 296, 298

Cycas (living) 296Cylindroteuthis 31 cynodonts 195, 294,

catscattle 270–1wild (living) 270

Caudipteryx 132–3, 136cave paintings 263, 270

caviomorphs 238Cedarosaurus 158Cenozoic era 144, 278centipedes 284centrosaurines 190Centrosaurus 125, 190Cephalaspis 38cephalochordates 33cephalopods 30Cerapoda 165cerapods 165Ceratodus 52ceratopsians 165, 185,186

ceratopsids 188, 190ceratosaurs 104, 105,108, 110

Ceratosaurus 108, 110cereal crops 310, 311cetaceans 195, 274Cetiosaurus 152chalicotheres 126, 254–5

chalk 312, 324chambered lizard see Camarasaurus

chamosaurines 191Champsosaurus 77Chaoyangsaurus 186Charniodiscus 14Cheiracanthus 47cheirolepidids 37Cheirolepis 48, 49chelicerates 26chelonians 74chewing the cud 266,269

Chiappe, Luis 346chicken mimic see Gallimimus

Chicxulub Crater 301chimaeras 36chimps 230Chondrichthyes 44chondrosteans 37chordates 15, 22, 32, 280

choristoderes 76, 77Christmas, Erwin 332chronometric dating328–9

cichlid (living) 51Cistecephalus 201civets (living) 216Clack, Jennifer 346clades 17, 18, 19cladistics 18, 350cladograms 8, 17, 19amphibians 56–7birds 138–9early tetrapods 56–7fish 36–7invertebrates 22–3ornithischians 164–5reptiles 70–1

saurischians 104–5synapsids 194–5vertebrates 34–5

Cladoselache 44Cladosictis 208classes 18classification 18–19, 352

Claudiosaurus 77clawsBaryonyx 114hoatzin (living) 141hoofed mammal 255Plateosaurus 150retracted (carnivore)214celidosaurus 168Therizinosaurus 126Troodon 136

clays 312Cleveland-LloydDinosaur Quarry, Utah119

climate see Earth facts boxes infossil timeline 278–311

climate, reconstructingancient 323

Climatiiformes 46Climatius 46, 47cloning 311club mosses 68, 322, 342fossil timeline 288, 290

cnidarians 22coal 11, 62, 342coccolith 324cockroaches 29coelacanths 34, 298, 340(living) 52, 53

Coelodonta 257Coelophysis 108, 347coelurosaurs 105, 120,122

Coelurosaurus 76, 77Colbert, Edwin H. 347cold-bloodedcrocodilians 92

Collenia 279colobids 229common index fossils327

Como Bluff, Wyoming317

comparative dating 326Compsognathus 120, 121,297

computer generatedimaging (CGi) 333

computer modeling forreconstructions 333

computerizedtomography (CT) 321

concretions 312Condylarthra 244condylarths 245cones club moss 322conifer 342cordaite 289

368

REFERENCE SECTION

202–3Cynognathus 202, 294

Ddace (living) 306Daeodon (formerlyDinohyus) 264, 265

damselfish (living) 51Dana, James Dwight 347Dart, Raymond 347Darwin, Charles 16, 17,246, 347

datingchronometric 328–9comparative 326–7fission-track 329radiocarbon 329, 352radiometric 328using microfossils 327

Daubentoniamadagascariense 227

daubentoniids 227dawn little-wing bird see Eoalulavis

De Pauw, Louis 348deceptive lizard see Apatosaurus

decay processes 328deciduous trees 302, 304

deer 240, 268–9Deinogalerix 225Deinonychus 134–5Deinosuchus 92, 93deinotheres 259Deinotherium 259Dendrerpeton 60dentary bone 202, 203deoxyribonucleic acid see DNA

Derbyia 290derived characters 17, 18, 19

Desmana moschata 224desmans 224Desmatosuchus 91desmostylians 195, 251

deuterostomes 22Devil’s corkscrews 239Devonian age of fish 42period 278, 286–7plants 322, 342

Diadectes 66, 67diadectomorphs 35, 57, 66

Diadiaphorus 247Diapsida 341diapsids 71, 76–7Diatryma see Gastornis

Dicellopyge 294Dickinsonia 279dicynodonts 76, 200–1didolodontids 244Didolodus 244Didymictis 214

different lizard seeAllosaurus

different-tooth lizard see Heterodontosaurus

digits (fingers, toes) 56,58, 59, 98, 286

digs, fossil 313Diictodon 201Dilophosaurus 109“Dima” 262Dimetrodon 196–7, 199,203, 290

Dimorphodon 94, 95, 96–7

dinocephalians 76, 198dinoceratans 242–3Dinofelis 216, 217Dinohyus see Daeodon

dinosaur displays see reconstructingfossils, restoring fossils

Dinosauria 348dinosaurs 102–3, 298,344, 355and birds 144extinction of 300–1,344first 294heaviest 151, 158largest 152, 176longest 155rule of 296see also under individualtypes of dinosaur

Diplocaulus 64, 65diplodocids 149, 154–5Diplodocus 154–5diploe 258Diprotodon 206, 207, 309diprotodontids 206Diptera 350Dipterus 286Discosauriscus 67diversification 17DNA (deoxyribonucleicacid) 14, 17, 346, 357humans 236 mammoths/elephants 262whales/hippos 274

dodo 310Doedicurus 211dog jaw see Cynognathus

dog teeth see cynodonts

dogs 214, 220–1Dollo, Louis 348Dolly the sheep 311dolphin (living) 306Dong Zhi-ming 348dormice 240Dorudon 275double beams see diplodocids

Douglass, Earl 348Douglass Quarry, Utah348

Draco 77dragonflies 28

dromaeosaurids 134–5, 138

Dromiceiomimus 122dryosaurs 179Dryosaurus 178, 179dsungaripterids 98Dubois, Eugene 348duck-billed dinosaurs see hadrosaurs

duck-billed platypus(living) 205

dugong (living) 309Dunkle, D.H. 41Dunkle’s bony onesee Dunkleosteus

Dunkleosteus 41, 42Dutuitosaurus 60

Eear bones 194, 195, 200,302

early horns see protoceratids

earth lizard see Edaphosaurus

earth-shaking lizard see Seismosaurus

earthworms 23Eastmanosteus 287ecdysozoans 23echinoderms 22, 32, 288

echinoids 339Echioceras 30, 31echolocation 274ecological niches 324ecosystems 11, 324, 325Ecphora 339Ectoconus 245Edaphosaurus 197, 290Edentata 210Ediacara 279Ediacara fauna 14, 317,349, 356

Ediacara Hill, Australia 14, 317

Edmonton’s lizard see Edmontonia

Edmontonia 174, 175Edmontosaurus 103Edwards, Dianne 348egg-laying monotremessee monotremes, egg-laying

Egg Mountain, Montana351

egg thief see Oviraptor

eggs/eggshells 68dinosaur 130, 150, 161,182, 349, 351, 354

Elasmobranchii 36elasmosaurs 84Elsmosaurus 84, 85Elasmotherium 256Eldredge, Niles 348, 349

elegant jaw

see Compsognathuselements 328elephant bird 144Elephantidae 306elephant-shrews (living)212

elephants 240, 250,258–9, 306dwarf 241(living) 260, 262see also mammoths

Elephas falconeri 241Elginerpeton 58Elginia 72Elrathia 338elytra 28Emausaurus 168Embolotherium 255embryos 22, 68, 156, 354emmer 311emu mimic see Dromiceiomimus

enantiornithines 139,142

entelodonts 264, 265environments 11, 324Eoalulavis 143Eobasileus 242Eocene epoch 278,302–3

Eoraptor 106Epigaulus 238, 239epitheres 195epoccipitals 190epochs 327Equisetites 288Equisetum (living) 286Equus 243eras 278, 327Eremotherium 210Erlikosaurus 127erosion 10, 13, 313Eryopids 63Eryops 11, 63estemmenosuchids 199Estemmonosuchus 198, 199Estonioceras 282eukaryotes 14, 279nucleus 14organelles 14

eumetazoans 32Euoplocephalus 176, 177Euramerica 289, 291eurypterids 26Eurypterus 26Eusthenopteron 53, 58Eustreptospondylus 112Evernia prunastri 310evolution 14–15, 16–17,319birds 139by jumps 17Darwin’s theory 16, 347fish 37human 347, 349insects 28–9invertebrates 23limbs and digits 59living animals 16ornithischians 165plants 322

reptiles 71saurischians 105synapsids 194, 195tetrapods 57vertebrates 35

evolutionaryrelationships 320

excavation of fossilsprotective gear 314removing/freeing fromrock 314, 315, 318, 319techniques 314–15tools 314transporting fossils 314,315wrapping fossils 315see also stabilization offossils

expeditions, fossilfinding 312, 313

exposure of rocks 313extinction 10caused by humans 308,310see also mass extinctions

eyesichthyosaurs 87insects 28pterosaurs 95trilobites 25, 280Troodon (dinosaur) 136

Ffamilies 18fan sails 52Farlow, Jim 348feathers 132, 140Archaeopteryx 140dinosaurs 132–3, 134,135, 137evolution of 105

feathery filaments,dinosaur 127, 135

feet see hoofed mammals

feliforms 216–17Felinae 217fenestrae 72ferns 68, 322, 342fossil timeline 288, 296,298, 299see also seed ferns

Ficus 303figs 303filter feeders 282finding fossils see fossil finding

finger nails 229fingers see digits

fins 34, 37, 340fish 37, 41, 47, 49ichthyosaurs 86mosasaurs 79

first arrivals of differentprehistoric life onEarth 279

fish 304, 340, 344

369

INDEX

first 32cladograms 34–5, 36–7evolution of 37with “arms” 40see also under differenttypes of fish

fission-track dating 329Flaming Cliffs, GobiDesert 317

flat lizard see Plateosaurus

flatworms 22flightbats 224birds 139insects 28, 29

flippers 79, 82, 83flowering plants 183,309, 322

footprints 58, 148, 312,352

Foraminifera 324, 327forest mouse see Hylonomus

forests bamboo 311coniferous 308destruction of byhumans 310rain forests 308temperate 302, 304,305, 306, 307, 310tropical 288, 302

fossil anatomy 319, 320fossil animals, restoring332–3

fossil blocks 314, 315fossil collecting see fossil hunting

fossil deposit 11fossil digs 313fossil expeditions see fossil finding

fossil finding 10, 312–13see also excavation of fossils

fossil hunters see fossil finding

fossil hunting, amateur334–5, 336–7cataloging and labelingfossils 336, 337cleaning fossils 337clothing 335equipment and tools335, 337examining fossils 337field notes 337fixing fossils 337geological maps 334places to look for fossils336research and reference334safe practices 335sieving for fossils 336storage of fossils 337wrapping fossils 336

fossil sitesexcavating see excavation of fossils

famous 316–17mapping 315recording 315walking, to spot fossils33

fossil timeline 278–311fossils 12–13cataloging fossils 318cleaning fossils 318common 327displays in museums358–9finding age of 326formation of 13identifying fossils 337illustration of fossils319in the lab 318–19index 327mass death 60models of fossils

see models of prehistoric life

myths about fossils 10naming fossils 317, 319restoration of 319restoring fossil animals332–3scientific descriptionsof 319studying 320–1types of 12see also excavation offossils, stabilization offossils

fossilization 13, 356four-limbed vertebrates286, 287

frills 189, 190, 191frogs 64, 294, 341fur 92, 308fused lizards see ankylosaurs

GGalápagos Islands 16,347

Gallimimus 103, 123, 320Galton, Peter 348gars (living) 17, 49Gaston, Robert 176Gastonia 176Gastornis (formerlyDiatryma) 303

gastropods see under molluscs

Gauthier, Jacques 348Gavialis (living) 92gavials (living) 92gelada (living) 228Gemuendina 40Genasauria 164genealogical tree 349genera (singular genus)18, 352

Genera Plantarum 352genetics 17, 311genets (living) 216

geographic isolation 324

geological maps 312,334, 356

geological timechart/timescale 278,326subdivisons of 327

geology 313, 346, 353see also geological entriesand comparative dating

gharials (living) 92giant lizard see Titanisgigantic lizards see titanosaurs

giant pandas see pandas

giant southern lizard see Gigantosaurus

Gigantosaurus 117Gillicus 51Gilmore, CharlesWhitney 349

Ginkgo (living) 294ginkgos 290, 294, 296,298

Giraffa camelopardalis 269giraffes 268, 269giraffids 268, 269gizzard stones 159, 187,320

Glaessner, Martin 349gliding 77glires 194glossopterids 294Glossopteris 290, 323Glossotherium 210glyptodonts 210, 211gnathostomes 34, 36goats 270–1Gobi Desert, Mongolia317, 344

gomphotheres 259, 260Gomphotherium 259Gondwana fossil timeline 281, 283,285, 287, 289, 291

Goniatites 289Goniopholis 341good strong fin see Eusthenopteron

gorillas 230Gould, Stephen Jay 349Graeophonus 289Granger, Walter 349graptolites 283, 284grasses 304, 306, 310grasslands 248, 252, 304,306, 308

grazers/grazingmammals 270–1, 304,306living 267

Great auk 308green algae 282, 284groupings of livingthings 18, 19

guenons 229gymnosperms 288, 290,296, 298

Gyracanthus 46

Hhabitats 11, 324, 325hadrosaurs 182–3, 299Haeckel, Ernst 349hagfish 36, 38Haikouella 33Halecostomi 37halkieriids 281Hall, James 349Hallucigenia 15hand fin see Cheirolepis

handsCamptosaurus 179five digits 56Iguanodon 180psittacosaurs 186saurischians 104, 105see also digits

hatchlings (dinosaur)150, 182, 184, 344, 351

Hayden, Ferdinand 350head chordate see cephalochordates

head crestsdinosaurs 109, 117,183, 299pterodactyloids 98, 99

head shields 39, 281, 340

heavy lizard see Barosaurus

hedgehogs 224, 225Heilmann, Gerhard 350Heliobatis 45Heliospongia 293Hemiaster 339Hemipristis 340Hennig, Willi 18, 350Henodus 81herbivorescamels 266caniforms 220deer 268diprotodonids 206first (diadectomorphs)66horses 304Iguanodon 181xenarthrans 210see also plant-eaters

herds 344and trackways 325dinosaurs 162, 182, 191

Herrera’s lizard see Herrerasaurus

Herrerasaurus 106, 107Hesperocyon 220Hesperornis 142, 341hesperornithiforms 139Heterodontosaurus 164,167

Hexaprotodon 264hide crocodiles 168dinosaurs 168, 172,173, 175

high camel

see AepycamelusHill, Dorothy 350Himalayas 305, 307Hipparion 146, 252–3,304

Hippopotamus 264lemerlei 264

hippopotamuses(hippos) 240, 264–5

Histoire Naturelle (Natural History) 346

Hitchcock, Edward 350hoatzin (living) 141hollow-tail lizard see coelurosaurs

Holocene epoch 278holocephalans 36holochroal eyes 25Homalocephale 184Home Quarry, Wyoming345

hominids 232, 234, 236,347, 349, 351, 352

Homo 232–3, 308erectus 232, 233, 234,348ergaster 232, 233, 316,348habilis (nowAustralopithecus habilis)231, 316heidelbergensis 234, 236neanderthalensis 234,235rhodesiensis 234sapiens 234, 236–7, 308

Homotherium 217hooves/hoofedmammals camels 266even-toed 264odd-toed 254–5predators 272–3primitive 244–5South American 246–7three-toed 252ungulates 195

Hoplophorus 211Hopson, James 351horn coresbovoids 270

horned dinosaurs 17,165, 184, 185advanced 190–1early 188–9

horned lizard see ceratosaurs

Horner, John 351horns (dinosaurs)abelisaurids 110ankylosaurs 174, 176ceratopsomorphs 190ceratosaurs 108dinoceratans 242, 243Neoceratopsia 188, 189paleomerycids 269protoceratids 268

horns (mammal) arsinoitheres 250bovoids 270brontotheres 254,

370

REFERENCE SECTION

255dinocephalians 198lepospondyls 64meiolaniids 74mylagaulids 238pronghorns 271rhinos 256 see alsoantlers

horses 304, 252–3(living) 243, 253horseshoe crabs 286horsetails 68, 284, 288,290, 342

Hovasaurus 77Howe Ranch, Wyoming345

humans 226, 232, 236–7,306, 308ancestors of modern230–1art 236, 237

hunting/causingextinctions 308, 310,311origins in Africa 237tools 236see also hominids, Homo

Hutton, James 350Huxley, Thomas 351hyenas 214, 216Hyaeodon 215Hybodus 45Hydrodamalis gigas 309

Hydrophilus 28Hylonomus 68, 69, 70hyopsodontids 245Hyopsodus 245Hypacrosaurus 182Hypolagus 239Hypsilophodon 103, 166,186

Hypsognathus 72hyracodontids 256hyraxes 250, 251

IIapetus Ocean 25, 281,283

Icaronycteris 223, 224, 225

ice sheets 283, 292, 309ichthyornithiforms 139ichthyosaurs 86–7, 294,296, 344

Ichthyosaurus 86, 87, 296

Ichthyostega 56, 58, 59,287

Ictitherium 216igneous (volcanic) rock312, 326

Iguanodon 114, 178,180–1, 348

iguanodontians 178Imperial mammoth see Mammuthus imperator

inclined fish

see Climatiusindex fossils 318, 327Indosaurus 110Indosuchus 110inheritance 17insectivores 195, 224–5xenarthrans 210

insects 28–9, 286in amber 343largest flying 68

invertebrates 338–9, 351cladogram 22–3evolution of 23

iridium 301, 344Irritator 114Isan lizard see Isanosaurus

Isanosaurus 152attavipachi 346

island giants and dwarfs240–1

isotopes 328, 329half-life 328

JJacobson’s organ 78Java Man 348jawed fish 37, 40, 284,286

jawed vertebrates 36jawless fish 38–9, 284,286, 340cladograms 34, 35, 36,37

jaws 34, 37Australopithecus boisei231Carnotaurus 111Compsognathus 121cynodonts 203desmans 224dinosaurs 103, 113, 116,164, 165, 166elephants 260, 261Homo heidelbergensis234placodonts 80pterodactyloids 98Tyrannosaurus rex124see also skulls and teethentries

Jefferies, Richard 32Jeholodens 205jellyfish 22jet propulsion 30, 31Jobaria 112Joggins, Nova Scotia 69

Johanson, Donald 351

Jurassiccommon index fossils327period 278, 296–7plants 342

Jurassic Park 333, 344

Kkannemeyeriines 200Kentrosaurus 170, 171keratin 256Kielan-Jaworowska, Zofia351

king of the tyrant lizardssee Tyrannosaurus rex

kingdoms 18Knight, Charles 332, 351Kronosaurus 82, 83K-T boundary 344Kvabebihyrax 251

Llaboratory(paleontology) 318–19safety equipment 319use of acids 319

lagomorphs 212, 238,239

Lamarck, Jean-Baptiste351

Lambe, Lawrence 351lambeosaurs 183Lambeosaurus 183lambei 351lamp shells (living) 290lampreys 34, 36, 38lancelets (living) 32, 33

land animals first 284fossil timeline 286–311

land bridge 307land plants fossil timeline 279–311see also plants

langurs 229lateral lines 59Latimeria 53Law of Irreversibility inEvolution 348

Lazarussuchus 77Leakey, Mary and Louis316, 352

Leidy, Joseph 352Leithia 240lemurs 226lens eye see PhacopsLeonardi, Giuseppe 352Lepidodendron 68, 322,323, 342

Lepidostrobus 322Lepidotes 50, 114Lepisosteus 49lepospondyls 35, 64–5Leptolepides 50Lesotho lizard see Lesothosaurus

Lesothosaurus 166, 167Leuciscus (living) 304Lexovisaurus 170Libby, Willard 352lichens 308, 310

lignite 68limbs 56, 58first development 35,287

limestone 283, 312, 339,342

Linnaeus, Carolus 18,19, 352

Linné, Carl von see Linnaeus, Carolus

lions, marsupial 207Liopleurodon 82lipotyphlans 224Liquidambar 307lissamphibians 35, 57,64–5

litopterns 244, 246, 247little shield lizard see Scutellosaurus

liverworts 284living mammal groupsegg-laying monotremes204, 205, 212placentals 204, 210, 212pouched (marsupials)206, 207, 208, 209, 212

lizard-hipped dinosaurssee saurischians

lizards 71gliding (living) 77

Lizzie the lizard 67lobe-finned fish 35,52–3, 56, 58, 286, 340

lobe fins 52lobopods 15Lockley, Martin 352long-face see Eryops

lophotrochozoans 23lophotrophorates 23lorises 226lower hind limb lizardsee Scelidosaurus

“Lucifer” 230“Lucy” 351Lufengosaurus 148lungfish 34, 52, 286Lycopsis 208Lydekker, Richard 353Lyell, Charles 353Lyme Regis, England316, 344

Lystrosaurus 200, 201

MMachaeroprosopus 91machairodontines 218mackerel 302Macrauchenia 246, 248–9Macrocranion 225Macrogenis 265Macrones 307Macropoma 298magnetic field, reversalof 328, 329

Maiasaura 182, 351Majungatholus 110, 111mammalian features,

typical 194mammals 194ancestors of 202biggest known 256, 272first 204–5fossil timeline 341hoofed see hoofed

mammalsplacental see placental

mammals/placentalspouched see marsupials

(pouched mammals)second fastest 271strange joint see

xernarthranssee also living mammalgroups

mammoths 262–3, 316Mammuthusimperator 263primigenius 262, 263

mangabeys 229maniraptorans 105, 122,132, 135, 136, 140

mantle, belemnites 31Mantell, Gideon 180Mantelliceras 338maple trees 304mapping see under fossil sites

maps see geological mapsMarginocephalia 165,185

marginocephalians 103,165

marine reptiles 70, 80,82, 84, 86, 296

Mariopteris 291Marrella 15, 281Marsh, Charles Othniel353

marsupials (pouchedmammals) 309American 208–9, 324Australian 204, 205,206–7, 309, 324cladogram 194(living) 204, 205, 206,212see also under livingmammal groups

Martínez, Rubén 161Maryanska, Teresa 345mass extinctions 278Cretaceous 300–1, 344Ordovician 284Permian 290, 292–3

mass death fossils 60mass spectrometer 328mastodon lizard see Mastodonsaurus

Mastodonsaurus 60, 61mastodons 10Mastopora 282, 342Matthew, William Diller353

Mayulestes 208meat-eating bull see Carnotaurus

meat-eating dinosaurs106, 117, 124

371

INDEX

megabats 225Megacerops 243Megaladapis 226megalancosaurs 89Megaloceros 268megalosaurs 112Megalosaurus 112–13,180, 346

Meganeura 11, 28, 29, 62Megatherium 210, 211Megazostrodon 295meiolaniids 74melon (in whales) 274meridiungulates 246Merychippus 252Mesoleuctra 29mesonychians 272mesonychids 273, 274Mesonyx 273Mesopithecus 229mesosaurs 73, 290Mesozoiccommon index fossils327era 278plants 322, 343

Messel, Germany 316,325

metailurines 216Metaldetes 280metamorphic rocks 312metamorphosis 23Metaxygnathus 58metazoans 14, 15metoposaurs 60Metriorhynchus 92, 93Meyer, Hermann von353

Miacis 214, 215miacoids 214, 216microbats 225microfossils 322, 327,344

microorganisms 279, 280

Micropachycephalosaurus184

Microraptor 135microsaurs 64microscopes (in the lab)318, 320, 321, 327

microscopic life 14microscopy 320, 321middle nail see Mesonyx

Miller, Stanley 353milleretids 72millipedes 68, 284, 288Minmi 175Miocene epoch 278,304–5

moa 144Mobergella 281models of prehistoriclifecasting 333, 337from imprints in rocks337

making 333plaster of Paris 3373-D modeling 333

using computers 333see also under Barosaurus

Moeritherium 258, 259moles 224mollusks 23, 30, 284gastropods 298, 339swimming 288, 289

Mongolia see Gobi Desert

mongooses 216monkeys 228–9, 304monotremes, egg-laying194, 205(living) 204, 205, 212

Montanoceratops 188moonrats 225Morgan’s tooth see Morganucodon

Morganucodon 204, 205Moropus 255mosasaurs 78–9Mosasaurus 10Moschops 198, 199mosses 284, 308molding 333, 337mouse lizard see Mussaurus

mud 312mud trap 118–19mudstones 312, 314multicellular organisms14, 279, 310

multituberculates 204Murchison, Roderick354

museum displays 333,358–9

Mussaurus 150mylagaulids 238Myliobatis 43Myotragus 240

Nnaked seeds 289, 290see also cones

Nanshiungosaurus 127natural selection 16, 347natural variation 16nautiloids 282Nautilus (living) 282neanderthals 234–5, 236brow ridges 233

necksdinosaurs 152, 154,155, 158, 159, 160plesiosaurs 82, 84prolacertiforms 88

nectrideans 64nematodes 23Neoceratopsia 188neoceratopsians 188Neochoerus 238neodiapsids 76, 77Neognathae 144neopterygians 48, 50,291

Neornithes 139, 144neornithines 139, 144

Neptunists 357nesting colonies(dinosaur) 182

nests (dinosaur) 130,150, 182, 344, 351

Neusticosaurus 295New World monkeys228, 229

Nicholson, H.A. 353Ninjemys 74Nipa (living) 302 node lizard see nodosaurids

nodes 19nodosaurids 174Norell, Mark 354nostrils dinosaurs 115, 179Macrauchenia(litoptern) 246plesiosaurs 82whales 275

Notelaps 325Notharctus 227nothosaurs 80–1Nothosaurus 80, 81notochord 32, 33, 280notoungulates 247Novas, Fernando 110

Ooak mosses 310, 304, 305oak trees 303Obruchevichthys 58occipital chignon 235okapi (living) 269Okapia johnstoni 269Old World monkeys 228,229, 304

Olduvai Gorge, Tanzania316, 347, 352

olecranon process 56Olenellus 25Oligocene epoch 278,304–5

omnivores 212, 220Onychiopsis 299onychophorans 23Oparin, Alexander 354Ophiacodon 288opisthosoma 26opossums (living) 208orders 18Ordoviciancommon index fossils327period 278, 282–3

organelles 14organic materials, datingof 329

origins of life on Earth353, 354

Ornithischia 164, 355ornithischians(dinosaurs) 103, 106,148, 186cladogram 164–5evolution 165

hipbones 103skull 103

ornithodirans 71, 90Ornitholestes 120, 121ornithomimids 122–3ornithomimosaurs 105ornithopod dinosaurs103, 165, 166, 178, 186

Ornithoracines 138, 143Ornithorhynchus 205Ornithothoraces 138Ornithurae 139ornithurines 139Orthograptus 283Osborn, Henry Fairfield354

Osmólska, Halszka 345Osmunda 342Osteoborus 220osteoderm 12osteostracans 39ossicones 268, 269ostrich dinosaurs 122–3Ostrom, John 354Otlestes 224overburden 314Oviraptor 130–1, 344philoceratops 130

oviraptorids 130–1, 132Ovis canadensis 271Owen, Richard 152, 246,332, 354

ox 270Oxydactylus 267

P Qpachycephalosaurs 165,184

Pachycephalosaurus 184,185

Pachydyptes 305Pachypteris 295pacing 267Padian, Kevin 354Pakicetus 274, 275paleobotany 322–3Paleocastor 239, 305Paleocene epoch 278,302–3

paleoecology 324–5Paleognathae 144paleomagnetism 329paleomerycids 268, 269

paleoniscoids 48Paleoniscus 291paleontologistsfinding fossils 313in the laboratory318–19studying fossils 320–1

paleontology 10–11Paleozoic era 278Paleoparadoxia 251paleopathology 121Paleothyris 68palm trees 302, 343palpebral bone 178

palynology 323pampas 306panameriungulates 246pandas 311giant 221

Panderichthys 52Pander’s fish see Panderichthys

Pangaea 290, 291, 292,295, 297, 357

Panochthus 211pantodonts 212, 213,242

Paracarcinosoma 285Paraceratherium 256Paracolobus 229Paradoxides 25Paranthropus 231parareptiles 70, 72–3, 74Parasaurolophus 183pareiasaurs 72, 73Parka 284parrot lizards see psittacosaurs

Patagopteryx 139peat 68peccaries 264–5pecorans 264peer-review 319Pelecanimimus 123Pelorovis 270pelican mimic see Pelecanimimus

pelycosaurs 194, 196penguins 305periods 278, 327perissodactyls 195, 252, 254

permafrosts 312, 316Permianmass extinction 292–3

period 278, 290–1Phacops 24, 25, 287Phanerozoic Eon 12, 15phenacodontids 244Phenacodus 244, 245Phimnin 261Phiomia 258, 259Phoberomys 238Pholidocercus 225phorusrhacids 145Phosphatherium 258phyla (singular phylum)18, 349

phylogeny 319phytosaurs 90, 91Picea 308pigs 264–5Pikaia 15, 280pikas 238, 239, 240Pinguinus impennis 308Pisanosaurus 106Pithecanthropus erectus 349

placenta 210, 194placentalmammals/placentals194, 204, 210–11,212–13, 324

Placerias 201placochelyids 81

372

REFERENCE SECTION

placoderms 36, 40, 286,287armored 284

placodonts 80–1Placodus 80plankton 282plant-eatersdinosaurs 158, 162rabbits and rodents 238small bipedal 166–7see also herbivores

plants 342–3, 348, 356ancestors of 282evolution of 286, 322Carboniferous 62first 284flowering 183, 322identifying fossil 322see also land plants,paleobotany

plated dinosaurs 170–1Plateosaurus 103, 150,151

plates see armor plates, bony plates

Platybelodon 260–1platyhelminths 22Platypterygius 86platyrrhines 228Platystrophia 339Pleistoceneepoch 278, 308–9

protozoans 324plesiadapids 226Plesiadapis 226, 227plesiosaurs 295, 344long-necked 84–5short-necked 82–3

Plesiosaurus 82pleurodires 75Pliocene epoch 278pliosaurs 82–3polacanthids 174, 176pollen 232, 233populations, interactionbetween 325

poriferans 22posturesprawl (reptiles) 120upright (dinosaurs) 102

potassium-40 isotope 328pouch Pterandon 98

pouched marsupials see marsupials(pouched mammals)

prairie 304Precambrian time 279, 344algae 322

predators dinosaurs 106, 117, 124phorusrhacids 145

predentary bone (jaw)103, 164

prehensile tails 229prehistoric landscapesrestorations of 332

premaxillae 35, 57

Prenocephale 185Presbyornis 145Prestosuchus 90priapulids 15primates 302primitive 226–7see also apes, monkeys

Priscacara 51, 340proboscideans 195,258–9

procolophonids 72Prodinoceras 242Proganochelys 74prokaryotes 14, 279prolacertiforms 88, 89Prolagus 240Promissum 283pronghorn 271prosauropods 106, 148,149, 150–1key features 148, 150

prosoma 26Prosqualodon 275Protoceras 268Protoceratops 130, 135,188–9, 344

Protodonata 62Protohydrocoerus 238Protopithecus 229proto-pterosaur 94Protostega 299Protosuchus 93protozoans 324Psephoderma 81Pseudaelurus 218psittacosaurs 186Psittacosaurus 186–7Pteranodon 98, 99Pteraspis 38, 340pteridosperms 295pterodactyloids 98, 344Pterodactylus 296Pterodaustro 98pteroid bone 98pterosaurs 88, 346advanced 98–9, 296early 94–5, 96–7, 294

Pterygotus 26, 27punctuated equilibria17, 348, 349

Purgatorius 226pycnodontiforms 37Pygostylia 143pygostyle 138, 143Quercus 305Quetzalcoatlus 98, 99

Rrabbits 238–9 (living) 212

raccoons 220radioactive decay 328,329

radioactive uranium see uranium, radioactive

radioactivity 328radiocarbon dating 329,352

radiometric dating 328,329

Ramoceros 271Rancho La Brea tar pits,California 220, 317

Ranunculus 309Raphus cucullatus 310rat fish 44ratites 144rauisuchians 90ray-finned fish 34, 37,340advanced 50–1early 48–9fossil timeline 286, 288,291, 294

ray fins 52rays 36, 42–3, 294, 296sword 51

reconstructing ancient climates 323ancient communities324ancient environments11, 324ecosystems 11, 324, 325

reconstructing fossils330–1casting 330final assembly 331framework support 331molds 330see also restoring fossilanimals

Red Deer River, Alberta345

reef builders 282, 293reefs 289, 290algae 342

replica fossils see reconstructing fossils

reptiles 35, 68, 346anapsid 341cladogram 70–1diapsid 341early crocodile group90–1early ruling group88–9, 92evolution 71first 288skulls 70, 71see also marine reptiles

reptiliomorphs 35, 57,66–7, 68

resinous sap 343restoring fossil animals322–3

research 332see also models ofprehistoric life

Rhacolepis 325Rhamphorhynchus 95rhenanids 40rhinoceroses 256–7(living) 256

rhizomes 287rhizophores 322, 323rhynchosaurs 88, 89, 106Ricqlès, Armand de 355ridges

horned lizards 109Riojasaurus 151Riversleigh quarry,Australia 317

rock nodules 336strata 326, 356

rocks 12, 324, 350, 354age of 328chemical changes 12,13classification of layers278dating, using pollen323decay of elements 328erosion 10, 313exposure 313maps of 312oldest known 328types of 312see also rock strata

rodents 238–9, 302, 305Romer, Alfred Sherwood355

roof lizard see Stegosaurus

rostral bone 165, 186roundworms 23rumination 266ruminants 266runninghoofed mammals 244,247

rhinoceroses 256Russell, Dale andDonald 127

russellosaurines 78

Ssaber-teeth 208, 209saber-toothed cats 216,217, 218–19, 307

Sacabambaspis 38Sagenocrinites 285salamanders 64salmon 310Salta lizard see Saltasaurus

Saltasaurus 12, 160sand 312sandstones 312, 314sarcopterygians 34, 37,52

satellite images 312Saurians 353Saurischia 355saurischians 103, 106,148cladogram 104–5evolution of 105pubic hipbones 103

Sauropelta 175sauropodomorphs103,104, 148–9

sauropods 148, 149, 150early 152–3key features 149

Sauropsida 351Sauropterygia 80, 82sauropterygians 80, 295Saurosuchus 106savanna 304scale bones 340scalesadvanced ray-finnedfish 50Edmontonia 174enameled 48, 49, 50, 53glyptodonts 211 see also skin

scanning electronmicroscopes (SEMs)321

Scaphonyx 89, 106scavengers 30, 120, 219Scelidosaurus 103, 168,169

schizochroal eyes 25Schizoretepora 338scientific names 319scientific papers 319scombroids 302scorpions 68, 288, 284see also sea scorpions,whip scorpions

sculling 79scurfy scales see Lepidotes

Scutellosaurus 168, 169scutes see bony scutesScutosaurus 73scythe lizard see Therizinosaurus

sea floor, and formationof rocks 312

sea lilies 285sea lizards see mosasaurs

sea scorpions 26–7, 285,292

sea urchins 284, 298, 339

seabirds 142, 308seacows 250, 302hunting of 311

Steller’s 309sea lions 221seals 220, 221, 306hunting of 310

seas, ancient 324Sedgwick, Adam 355sedimentary rocks/strata10, 326fossils in 312, 316types of 312

sediments 11, 12, 13, 69seed ferns 286, 288, 295,343

seeds 322, 323, 343see also naked seeds

Seeley, Harry Govier 355Segnosaurus 127Seismosaurus 155Sequoia 343Sereno, Paul 355seymouriamorphs 35,57, 67

shale, fossils in 69, 338,

373

INDEX

342shared features 17sharks 36, 40, 44–5, 288,294first modern 296spiny 34, 36, 46–7, 284

Sharovipteryx 92sharp point lizard see Kentrosaurus

sheep 270–1shell, parts of 68amnion 68buoyancy 30, 31gas-filled chambers 30,289phragmocone 31

shells 68, 280, 338, 339shield bearers see thyreophorans

shield lizard see Scutosaurus

shielded lizard see Sauropelta

shovel-tusker see Platybelodon

shrew opposums 208,209

shrews 212, 222, 226Shokawa 77Shuo lizard see Shunosaurus

Shuvuuia 142Siamotyrannus 125Siberia 316Siderops 61Sigillaria 69Silurian 354common index fossils327land plants 342period 278, 284–5

Simpson, GeorgeGaylord 366

Simolestes 82single-celled organisms14

Sinokannemeyeria 200,201

Sinornithosaurus 135, 136sirenians 195site maps 315sivatheres 269skates 44skeletal reconstructions Cetiosaurus 152Oviraptor 131Therizinosaurus 126–7

skeletons (amphibians)emnospondyls 11, 60

skeletons (birds) 138Archaeopteryx 140Presbyornis 145

skeletons (dinosaurs)Albertosaurus 125Allosaurus 102–3Apatosaurus 148–9, 349Bambiraptor 137Camarasaurus 156Coelophysis 108Deinonychus 134Diplodocus 154

Herrerasaurus 107Lufengosaurus 148Ornitholestes 121Ornithominus 122Protoceratops 188Psittacosaurus 186Shunosaurus 153Stegoceras 184Triceratops 191Troodon 137Tuojiangosaurus 170Tyrannosaurus rex 124

skeletons (fish) cladograms 34, 36

skeletons (mammals)Edaphosaurus 197hominid 232Lycopsis 208Macrauchenia 246Megaladapis edwardis226Megaloceros 268Moschops 198neanderthal 235Notharctus 227Paracolobus 229Sthenurus tindalei 206Toxodon 247Ukhaatherium 213uranothere 251Ursus spelaeus 221Vulpavus 214

skeletons (marsupials)Diprotodon 309

skeletons (reptiles)crocodilian 92ichthyosaur 86mosasaur 79trilophosaur 88turtle 74

skin sails/skin fins 114,197, 290, 291

skin, scalydinocephalians 198dinosaurs 110, 134,161, 183ichthyosaurs 86pterosaurs 95

Saltasaurus 12temnospondyls 60see also feathers, hide

skull (amphibians)Acanthostega 59Diplocaulus 64, 65

skull (birds) 139skull (dinosaurs) 117,164, 165Baryonyx 115Brachiosaurus 159Camarasaurus 157Camptosaurus 178Centrosaurus 190Compsognathus 121Cynognathus 202Dilophosaurus 109Dimetrodon 203Edmontonia 175Edmontosaurus 103Euoplocephalus 176hadrosaurs 183Majungatholus 111

pachycephalosaurs 184, 185Protoceratops 188Psittacosaurus 187Shunosaurus 153stegosaurs 180titanosaurs 161Triceratops 191Tyrannosaurus rex 124

skull (mammals)Australopithecusafricanus 230Bienotherium 203bovoids 271Broken Hill 234brontotheres 254dicynodonts 200, 201dinocephalians 198,199elephants 259Equus 241hippos 264Homo erectus 233Homo ergaster 348Homo neanderthalensis233Hyaenodon 215Hypolagus 239Ictitherium 216mammoths 262mastodonts 195Megacerops 241mesonychians 272Neochoerus 238Osteoborus 220peccaries 265pelycosaurs 196protoceratids 268Smilodon 216Thalassoleon mexicanus221Thylacoleo 207Tremacebus 229Trogosus 213Uintatherium 240, 241whales 273, 275

skull (reptiles) 35, 70, 71amniote 69crocodile 15meiolaniids 74plesiosaurs 82, 84Procolophon 72rhynchosaurs 89younginiforms 76

slothsground 210, 211tree (living) 210

Smilodon 216, 217,218–19, 307

Smith, William 356snakes 71, 79, 298soft-bodied animals 13,279, 280

Solnhofen, Germany297, 316

sonar 224South Americahoofed mammals 246–7ungulates 195

Southern Cross lizard see Staurikosaurus

Struthiomimus 122Stupendemys 75sturgeon 49Styracosaurus 190, 191suborbital fenestrae 70Suchomimus 115suiforms 264, 265sun ray see Heliobatissupercontinent 357fossil timeline 290, 291,292, 295, 357

Supersaurus 155supramaxilla 37swamp forest,Carboniferous 11, 62–3

swampland, Cretaceous183

swim bladders 50, 52swimmingichthyosaurs 87jawless fish 38molluscs 282mosasaurs 79

sweetgum trees 307symbiosis 14Symmorium 288snyapsid opening 194synapsids 35, 68, 194,202, 351cladogram 194–5early 196–7, 288evolution of 194, 195fossil timeline 290, 294,296

Syndyoceras 268Synthetoceras 268Systema Naturae 18, 352

TTaeniolabis 204taiga 308tail chordates 33tail feather see Caudipteryx

tail spikesstegosaurs 172

tailsbirds 138dinosaurs 148, 152,154, 176, 177, 348early primates 226meiolaniids 74monkeys 229sauropods 153

tetanurans 112–13Tanystropheus 88, 89taphonomy 10tapinocephalids 198, 199tar pits (Rancho LaBrea) 317

Tarbosaurus 125, 128tardigrades 23tarsiers (living) 228Tatisaurus 168Taung skull 230, 347teethanthropoids 228bears 341

species 18, 19, 352change over time 16, 17

sphenacodontids 199spiders 286, 288spikesankylosaurids 176ankylosaurs 174centrosaurines 190parareptiles 72, 73stegosaurs 170turtles 74

spinesbarbed 43, 45fin 45, 46, 50mosasaurs 79ornithopods 179sharks 46, 4stegosaurs 171, 172Wiwaxia 281

spinosaurs 50, 114–15Spinosaurus 114, 115spiny sharks see under sharks

sponges 15, 22, 32, 290,293

spores 287, 322, 323, 342Sprigg, Reg 356Sprigginia 14squamates 76spruces 308stabilization of fossilsglue or resin 315, 318wrapping in plaster ofParis 315

stance see posturestarfish 22Staurikosaurus 107stay apparatus 253Stegoceras 184, 185stegosaurs 164, 168, 170,172

Stegosaurus 170, 172–3Stenomylus 266Stenopterygius 86Stensen, Niels 356steppe 306Sternberg family 351,356

Steropodon 205Stethacanthus 45, 288sthenurines 206Sthenurus tindalei 206Stigmaria 322stingrays 43, 45stomach contents 325of an ichthyosaur 86of a placoderm 286of a pliosaur 83of a younginiform 77

stomata 323stoneflies (living) 33Stopes, Marie 356strangler figs 303stratigraphic history 326stratigraphy 326, 347,356

stromatolites 14, 279,280, 322

Strophomena 282Struthiocephalus 198

374

caninelike 70, 71carnivores 214, 216conodonts 33, 283cynodonts 202, 203dicynodonts 201dinoceratans 242dinosaurs 165, 166,167, 170, 182horses 252Iguanodon 348mammals 196mosasaurs 78nothosaurs 80ornithischians 164, 165Panderichthys 52parareptiles 72Pelecaniminus 123Plateosaurus 151plesiosaurs 82, 84pterodactyloids 98pterosaurs 94rabbits/rodents 238sharks 45synapsids 290teleosts 296, 298Tyrannosaurus rex 124see also canine teeth,carnassials

Teleoceras 257teleosts 37, 50, 51, 297telson 26, 27Temnodontosaurus 87temnospondyls 35, 57,60–1, 64, 68

temperature control197, 290

tentacles, belemnites 31teratorn 144tergites 26terrapins 75terrible cat see Dinofelis

terrible claw see Deinonychus

terrible heads see dinocephalians

terrible horns see dinoceratans

terror crane see phorusrhacids

Tertiarycommon index fossils327plants 342

tetanurans 104, 105, 108,112–13, 120see also spinosaurs

Tethys, sea of 295tethytheres 195, 250Tetralophodon 306tetrapods 35, 36, 67early 58–9early, cladogram 56–7evolution 57, 356see also amniotic egg

Tetrapteryx 345Thalassocnus 210Thalassoleon mexicanus221

thecae 283Theosodon 247

therapsids 73, 202, 204,291see also dinocephalians

theriodonts 202therizinosaurs 126–7,128–9

Therizinosaurus 126–7,128–9

Theropithecus 228, 229oswaldi 228

theropods 103, 108, 140early 106–7, 148stiff-tailed 126trackway 12

thick-headed lizard see pachycephalosaurs

Thoatherium 247three knob teeth see tritylodonts

Thrinaxodon 202, 203thunder lizard see Brontosaurus

thunnosaurs 86thylacines 206Thylacinus 206, 324Thylacoleo 207thylacoleonids 207Thylacosmilus 208, 209thyreophorans 103, 164, 165, 168

tillodonts 212, 242time chart, geological278

timeline bar 9Titanis 145, 146–7Titanohyrax 251Titanophoneus 198, 199titanosaurs 160–1toes see digitstomography 321toolsin excavations 314in the laboratory 318,319

toothplates 45, 52tortoises 74, 75giant (living) 16

Toxodon 247toxodonts 247trace fossils 12Trachyphyllia 338tracks/trackways amphibians 352dinosaurs 179, 183, 352first four-footed 286sauropods 344theropods 12, 325

treesfossil timeline 286, 302, 304, 305, 307, 323, 343

Tremacebus 229Triadobatrachus 64Triassic period 278,294–5

Triceratops 191triconodonts 204, 205trident tooth see Thrinaxodon

Trigonocarpus 343trilobites 23, 24–5fossil timeline 280, 284, 286, 287, 288, 292, 338

trilophosaurs 88Trilophosaurus 83Trimerorhachis 60Trionyx 341Triticum 311tritylodonts 203trochozoans 23Trogosus 213Troodon 136, 137troodontids 136trunks amphibious rhinos 256elephants 258, 259, 261

tubers 288tunicates (living) 33Tuo River lizard see Tuojiangosaurus

Tuojiangosaurus 170Turkana boy (hominidskeleton) 232

turtles 74–5, 341ancestors of 72, 294(living) 75sea 299see also placochelyids

tusksdicynodonts 20, 201dinoceratans 242, 243dwarf elephants 241elephants 258, 259,261, 306mammoths 262temnospondyls 61

two dog teeth see dicynodonts

two-ridge lizard see Dilophosaurus

two types of teeth see Dimetrodon

tylopods 264Tylosaurus 78, 79tyrannosaurids 117,124–5

tyrannosaurs 126Tyrannosaurus rex 124–5,345, 354

tyrant lizard see tyrannosaurids

UUintah beast see Uintatherium

Uintatherium 242–3Ukhaatherium 213unconformities 326ungulates 195, 244uranium-235 isotope 328uranium-238 isotope 329uranium, radioactivedecay 328, 352

uranotheres 250–1Uranotheria 250urochordates 33

ursines 221Ursus spelaeus 221

VValen, Leigh van 356Valley of the Moon,Argentina 317

vascular plants 284, 349Velociraptor 135, 189, 344velvet worms 23Vendian fauna 14, 278,279

Ventastega 56, 58vertebraeof early placentals 210of Elasmosaurus 84of ornithopods 179

vertebrae, parts of 34, 56centrum/centra 53neural spines 149, 153tail/chevrons 149, 152,154zygapophyses 153

vertebrates 36, 340–1bird 341cladogram 34–5evolution 35, 286four-limbed 52, 286jawed 34limb-bearing see tetrapods

viverrids 216volcanic activity end of Permian period292rocks 312, 326, 329

volcano tooth see Vulcanodon

Vulcanists 357Vulcanodon 152Vulpavus 214

WWalcott, Charles D. 15,357

walkingaustralopithecines 230camels 266, 267Caudipteryx 133rausuchians 90sauropods 149

Walking with Dinosaurs333

walruses 221warm-bloodedcynodonts 202dinosaurs 102mammals 204pterosaurs 94

water bears 23Watson, James 346, 357

weasels 220websites 359Wegener, Alfred 357

weigeltisaurids 77well-armored head see Euoplocephalus

Werner, AbrahamGottlob 357

Westlothiana 67, 288Wetherellus 302whale lizard see Cetiosaurus

whales 264, 273, 274,303blue 311early 274–5modern 306Right 306

whaling 310, 311wheat 311whip scorpions 287Wilkins, Maurice 346,357

Williamsonia 297, 343Williston, SamuelWendell 357

wing shield see Pteraspis

wingsazhdarchids 99bats 222, 224, 302birds 144insects 28, 29pterosaurs 94, 95, 98

Wiwaxia 281wolves (singular wolf)dire 220, 221, 324marsupial (pouched)206

Woodward, John 357woollymammoths 262rhinoceroses 257

work person see Homo ergaster

wounding tooth see Troodon

X Y Zxenarthrans 194, 210–11Xenotarsosaurus 110Xiphactinus 51X-ray technology 318,320, 321

Xystridura 280Yang Zhongdian 348Yaverlandia 184Youngina 76younginiforms 76Zalambdalestes 212, 238,298

zircon crystal 329zones 327zooid 283Zosterophyllum 287, 342zygapophysis 56, 59

REFERENCE SECTION

375

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Position key: c=center; b=below;l=left; r=right; t=top; a=above; f=far

Aero Vironment Inc: MartynCowley 99bl;

American Museum Of NaturalHistory; 10clb, 45tl, 76bl, 93c,126bl, 155tl, 157cr, 161br, 208bl, 212-213b, 216bl, 220cl, 221tl, 221tr,226bl, 227bl, 238cl, 239tr, 239bc,246cb, 247br, 251br, 254tr, 263cr,264bl, 264br, 265tl, 271cr, 271bc,272bl, 313bl, 317tl, 319bl,321cr(below), 325tc, 332cr, 332br,344tl, 344bc, 349br, 351c, 352cl,355tl; A. E. Anderson 86bl, 257br;AMNH Photo Studio 196bl, 197bc,199br, 200tr; J. Beckett 134cr(above); J. Beckett/Denis Finnin90-91; Bierwert & Bailey 91bl;Blackwell/Finnin/Chesek 124bl; C.Chesek 2bl, 48bl, 60bl, 135cr,286-287c; Jim Coxe 28c; Mick Ellison130bl; D. Finnin/ C. Chesek 197t;D.Finnin 3b, 38b, 40cl, 40br, 44c,49tr, 95cr, 130tr, 135tr, 229tr 229cb,288c; Kirschner 78-79t; Menke317tr; Rota 79bl;

Ancient Art & ArchitectureCollection: 257tr, 263tc;

Aquila Photographics: J.J. Brooks141tr;

Ardea London Ltd: FrancoisGohier 199tc;

Barleylands Farm Museum: 35tr;

J. Beckett: 142tc;

BBC: 23tc;

Bridgeman Art Library, London/ New York: 237tl;

Bristol City Museum and ArtGallery: 168tr;

British Antarctic Survey: ChrisGilbert 324tc;

Carnegie Museum of NaturalHistory: Mark A.Klinger 148t,170bl, 205cr;

Jean-Loup Charmet: 10t;

Robert Clark: 161tl;

Cleveland Museum of NaturalHistory: 41bc;

CM Studio: 201br;

Bruce Coleman Collection: 248-249, 310-311t; Mark Carwardine310-311c; Sarah Cook 227tc; JanosJurka 172-173; Steven Kaufman

292bl; Hans Reinhard 49br; JensRydell 225tr;

S. Conway Morris: 279bl, 280bl,280-281c, 281tc, 281cr;

Corbis: 14cl, 16tr, 16cb, 16br, 18tr,18c, 18l, 252-253, 260-261, 292cl,335br, 336b, 345tr, 350bc, 351tr,352tc, 353bc, 355bc, 357bl;O.Alamany & E.Vicens 316br; TomBean 12br, 148br, 218-219;Jonathan Blair 316cla, 316clb;Gianni Dagli Orti 270bl; JuanEcheverria 10bc; Marc Garanger240-241; Derek Hall/Frank LanePicture Agency 312tr; DaveG.Houser 317tc; Peter Johnson122tc; Bob Krist 222c; DiegoLazama Orezzoli 317bc; ThePurcell Team 267tl; Charles O'Rear317br; Martin B.Withers/FrankLane Picture Agency 316bc;

Peter Cormack: James L. Amos280tr; Layne Kennedy 281tr;

Esto Photographics: ScottFrances 359br;

Mary Evans Picture Library:357tc;

Exhibit Museum of NaturalHistory, University of Michigan:292-293;

Getty Images Stone: EarthImaging 316cr;

Graves Museum: 137br, 137t;

Dr. Pat Herendeen: 321bc;

John Holmes: 103tl, 333tl, 333tc,333cl, 333cr;

Hulton Archive: 332tr, 345bc,346ct, 347cl, 347cb, 349tr, 354tr,354bc, 356cb;

Hunterian Museum: 2c, 11tr,34ca, 39bc, 279c, 302tc, 45br; Dr. Neil D.L. Clark 283tl;

Gerado Kurtz: courtesy ofUniversity of Madrid 143bl;

Dave Martill: 83tr;

Museo Arentino De CirendasNaterales, Buenos Aires: 150tr;

Muséum National d’HistoireNaturelle: Paleontologie (Paris),D. Serrette 11bl;

Museum of the Rockies: BruceSelyem 136br;

N.A.S.A.: 312b;

National Museum of NaturalHistory/SmithsonianInstitution: 167tr;

National Museum of Wales:

262bc;

The Natural History Museum,London: 3t, 13tr, 23tcr, 31tr, 32c,37tr, 45c, 45cr, 45clb, 64bl, 74bl,80b, 82tr, 87bl, 87tr, 89br, 94cl,124br, 140c, 155tr, 168bl, 168cr,194tr, 207br, 216cl, 217tr, 224bl,225bl, 230l, 231c, 231br, 233tc,233tr, 234bl, 235tl, 235tr, 236tr,242bl, 247tr, 261tr, 273tr, 275tl,279t, 282bl, 282t, 283bl, 284tc,284bl, 285cl, 285c, 286bc, 287bl,288bc, 289bl, 290tc, 290br, 291cr,291bl, 291t, 294tr, 294c, 294br,295tr, 295cl, 295bcb, 296c, 296t,297tr, 297cr, 297bl, 298c, 298bc,298tc, 299c, 299cr, 299bl, 302c,302br, 303c, 303bl, 303tr, 304tc,304c, 304br, 305cr, 306tc, 306cr,307cr, 307bl, 307t, 308c, 308b, 308tc,309t, 313br, 313tr , 318cr, 318bl,318br, 340cl, 340cr, 340bc, 340t,341tr, 341bl, 341br, 342tr, 342cl,342cr, 342bl, 343cl, 343b, 358bl;

Nature Magazine: 319br;

N.H.P.A.: 96-97; Daniel Heuclin300-301; Trever McDonald 44-45;

Oxford Scientific Films:Hjalmar R. Bardarson 292tr; MaxGibbs 48tr; Mark Jones 272tc;Maurice Tibbles 92br; Norbert Wu33tr;

Popperfoto: Reuters 316tc;

Dr. Mark A. Purnell, Universityof Leicester: 3bc;

Luis Rey: 127cr;

Royal British ColumbaMuseum: 195trc, 262-263;

Royal Museum of Scotland:34tr, 37cla, 59b, 286c, 288tr;

Science Photo Library: MartinDorhn/Stephen Winkworth 98-99;James King-Holmes 328bl, 329tl;David Parker 301tl; GeoffTompkinson 328cr;

Senckenberg Nature Museum:140l, 154c;

Paul Sereno/University ofChicago: 106bl, 117br;

J & B Sibbick: 14cb, 15cr;

Smithsonian Institute: 156tr;

South African Museum: CliveBooth 198bl, 201tr;

Topham Picturepoint: PressAssociation 311tr;

Royal Tyrell Museum: 136l,165tc;

University Museum, Oxford:19cl, 58c;

University Museum of Zoology,Cambridge: 58bc, 59t, 201c, 286tr,287tc;

Dr. RT Wells, FlindersUniversity: Photo by F. Coffa 206cl;

Professor Harry Whittington:319cr;

Yorkshire Museum: 153t, 200-201b, 230r, 231l, 232l;

Jerry Young: 57ca.

All other images © Dorling Kindersley.For further information see:www.dkimages.com

Specially commissionedillustraions:

Bedrock: 4bl, 5tl, 6tl, 7tl, 7tr, 11c,17tl, 21inset, 26-27, 29cl, 34ca,36ca, 37tl, 41c, 46-47, 55inset, 62-63, 65c, 68-69, 70tl, 70tr, 71tc, 71tr, 72-73, 74-75, 76-77, 78-79c, 80-81,82-83, 86-87, 88-89, 101inset, 104tl,104tr, 112-113, 116-117, 124-125,126-127, 128-129, 138tc, 143c, 143tr,145cr, 146-147, 150-151, 156-157,158-159, 160-161, 165tl, 178-179,184-185, 193inset, 194tl, 195tl,195tc, 196-197, 198-199, 202-203,204-205, 206-207, 208-209, 214-215,216-217, 217tr, 218-219, 220-221,222-223, 224-225, 226-227, 228-229,244-245, 246-247, 248-249, 252-253,254-255, 256-257, 260-261, 265r,266-267, 268-269, 270-271, 272-273,277inset, 332cr, 333br;

Tim Brown: 11cr, 14tr, 14bl, 64c,67c, 123tc, 140b, 144t, 145tr, 328tr,329cr;

Peter Bull: 17br, 19cb, 19la, 19fl,22-23bl to br, 25cr, 25tr, 30bl, 33tcr,34-35bl to br, 36-37bl to br, 47cb,56-57bl to br, 70-71bl to br, 90br,91t, 98bl, 98br, 99tr, 99tr, 104-105blto br, 138-139bl to br, 164-165bl tobr, 194-195bl to br, 255br, 256tr;

Gary Cross: 212-213tc;

Encompass Graphics: 236cr;

Malcolm McGreggor: 58c, 61rc,66-67t, 77c, 112bl, 127tl, 152b,208tl, 209l, 209br, 269tr, 274cr;

Luis Rey: 20-21, 52-53c, 54-55, 100-101, 192-193, 276-277;

Peter Visscher: 19tc, 19tl, 22cc,19ca, 34tc, 37tc, 56cl, 56tl, 56tla,57tc, 104tc, 138tr, 139tl, 139tc,139tca, 164tl, 195tl, 213cr, 213tr,324bl, 336t, 337tl, 337bl;

Robin Carter/Wildlife Art Ltd:81tl, 81bl, 82bl, 89bl, 94bl, 244bl,245tl, 245br.

PICTURE CREDITS

PICTURE CREDITS

376

ACKNOWLEDGMENTSWith special thanks to:

the American Museum of Natural History for their patient help and expert advice. In particular: Maron Waxman,

Editorial Director, Department of Special Publishing; Mark Norell,Curator of Vertebrate Paleontology; Jin Meng, Assistant Curator of

Vertebrate Paleontology

Special Photography:Denis Finnin, Roderick Mickens, and Megan Carlough for photography at the American Museum of Natural History;

Trish Gant of Dorling Kindersley for photography at the Yorkshire Museum

Dorling Kindersley Picture Library:Sally Hamilton, Rachel Holt,

Diane Le Grande

Jacket Design:Nicola Powling, Dean Price

Additional Editorial Assistance:Margaret Hynes, Carey Scott

Additional Design Management:Julia Harris, Gill Shaw

Additional Picture Research:Marie Osborn, Sarah Pownall

Additional DTP Assistance:Siu Yin Ho

Proofreading: Lee Simmons, Claire Watts

Design Assistance:Polly Appleton, Sheila Collins, Venice Shone

Index:Lynn Bresler

Documents

Dinosaurs and Prehistoric Life