Origins of BonesMineralization originated with mouthparts

The entire skeleton was mineralized much laterGnathostomes are vertebrates that have jaws

Jaws evolved from skeletal supports of the pharyngeal slitsAlso have enhanced sensory systems, mineralized endoskeleton, and paired appendages

Gill slits Cranium

Skeletal rods Mouth

Fig. 34.13

0.5 m

Fig. 34.14

Gnathostome EvolutionPlacoderms - extinct lineage of armored vertebratesAcanthodians - radiated during the Devonian period (closely related to osteichthyans)

(a) Coccosteus, a placoderm

(b) Climatius, an acanthodian

Class ChondrichthyansSkeleton composed primarily of cartilageCartilaginous skeleton evolved secondarily from an ancestral mineralized skeletonReproductive tract excretory system and digestive tract empty into a common cloacaIncludes: sharks, rays, and ratfish

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

(a) Blacktip reef shark (Carcharhinus melanopterus)

(b) Southern stingray (Dasyatis americana)

(c) Spotted ratfish (Hydrolagus colliei)

Dorsal fins

Pectoral fins Pelvic fins

Fig. 34.15

1

2

3

OstiechthyesNearly all have a bony skeletonWe informally call them fishControl their buoyancy with an air sac known as a swim bladderBreath by drawing water over gills

Located in chambers covered by a protective bony flap called the operculum

Fig. 34.16

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Nostril

Brain Spinal cord

Swim bladder

Dorsal fin

Adipose fin Caudal fin

Cut edge of operculum

Gills Kidney

Heart

Liver

Stomach

Intestine

Gonad

Pelvic fin

Anus

Anal fin

Lateral line

Urinary bladder

OstiechthyesClass Actinopterygii

Ray-finned fish - fins supported by long flexible rays modified for maneuvering, defense, and other functions

Class Sarcopterygii - have muscular, pectoral fins (ex. Coelacanths, lungfish, tetrapods)

Figs. 34.17 & 34.19

Yellowfin tuna (Thunnus albacares)

Red lionfish (Pterois volitans)

Common sea horse (Hippocampus ramulosus)

Fine-spotted moray eel (Gymnothorax dovii)

Lower jaw

Scaly covering Dorsal

spine

5 cm

TetrapodsGnathostomes that have limbs and feetOne of the most significant events in vertebrate history was when the fin of lobe-fins evolved into the limbs and feet of tetrapods

Fins became more limb-like

Have four limbs and feet with digitsHave ears for detecting airborne sounds

Figs. 34.20

& 34.21

Flat skull

Eyes on top of skull Head

Neck

Shoulder bones Ribs

Scales

Fin Fin skeleton

Elbow Radius

Humerus Ulna “Wrist”

Scales Fins Gills and lungs

Neck Ribs Fin skeleton Flat skull Eyes on top of skull

Tetrapod Characters

Fish Characters

Lungfishes

Limbs with digits

Amphibians

Amniotes

Silurian PALEOZOIC Devonian Carboniferous Permian

415 400 385 370 355 340 325 310 295 280 265 0 Time (millions of years ago)

Key to limb bones

Ulna Radius Humerus

Eusthenopteron

Panderichthys

Tiktaalik

Acanthostega

Tulerpeton

4

5

6

Class Amphibia4,800 speciesMost have moist skin that complements the lungs in gas exchangeName means “two lives” - undergo metamorphosis from aquatic larva to terrestrial adultOrder Urodela (salamanders) - have tailsOrder Anura (frogs, toads) - lack tailsOrder Apoda (caecilians) - legless and resemble worms

Figs. 34.20-34.21

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

(a) Order Urodela (salamanders)

(b) Order Anura (frogs)

Order Apoda (caecilians)

(c)

(a) Tadpole

(b) During metamorphosis

(c) Mating adults

ANCESTRAL AMNIOTE

Parareptiles

Turtles

Crocodilians

Pterosaurs

Ornithischian dinosaurs Saurischian dinosaurs other than birds Birds

Plesiosaurs

Ichthyosaurs

Tuataras

Squamates

Mammals

Reptiles

Synapsids

Diapsids

Archosaurs

Lepidosaurs

Dinosaurs

Saurischians

Fig. 34.25

AmniotesTetrapods that have a terrestrially adapted eggLiving members are reptiles, birds, and some mammalsNamed for the major derived character (amniotic egg)

Amniotic egg contains specialized membranes that protect the embryo

Also have relatively impermeable skin and the ability to use the rib cage to ventilate the lungsAppeared in the Carboniferous period

Fig. 34.26

Extraembryonic membranes

Shell

Amniotic cavity with amniotic fluid

Embryo

Amnion Allantois Chorion

Yolk sac

Yolk (nutrients)

Albumen

7

8

9

ReptilesIncludes tuatara, lizards, snakes, turtles, crocodilians, birds, and dinosaursHave scales that create a waterproof barrierLay shelled eggs on landMost are ectothermic - absorb external heat as main source of body heat (Birds are endothermic - keep body warm through metabolism)Date back to about 300 million years ago

First major group were parareptiles (large, stocky herbivores)As parareptiles dwindled, diapsids were diversifying (lepidosaurs and archosaurs) One surviving lineage of lepidosaurs is the two species lizard-like reptiles called tuataraThe other lineage are lizards and snakes

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Fig. 34.28

ReptilesSnakes - legless lepidosaursTurtles - have boxlike shells with upper and lower shields that fuse the the vertebrae, clavicles, and ribsCrocodilians - belong to the archosaur lineage that dates back to the TriassicBirds - archosaurs (almost every reptilian feature has undergone modification in adaptation to flight

(a) Tuatara (Sphenodon punctatus)

Australian thorny devil lizard (Moloch horridus)

(b)

(d) Eastern box turtle (Terrapene carolina carolina)

(c) Wagler’s pit viper (Tropidolaemus wagleri)

(e) American alligator (Alligator mississippiensis)

Fig. 34.27

BirdsMost obvious adaptations are wings and feathersProbably descended from theropods (group of small, carnivorous dinosaurs)

150 millions years ago - Arhaeopteryx (oldest known bird)

Order Struthioniforms (flightless birds)Demands of flight have caused a general body form to evolveFoot structure also shows variation Figs. 34.30-34.34

(a) Wing

Vane

Shaft

Forearm Wrist

Shaft Barb Barbule Hook (c) Feather structure

(b) Bone structure

Finger 1

Finger 2

Finger 3

Palm

Airfoil wing with contour feathers

Long tail with many vertebrae

Toothed beak Wing claw

10

11

12

MammalsAmniotes that have hair and produce milkGenerally have larger brains than other vertebrates of equivalent sizeEvolved from synapsids in the late Triassic

Jaw was remodeled (two bones that were part of the jaw joint were incorporated into the middle earLiving lineages originated in the Jurassic but did not undergo significant adaptive radiation until after the Cretaceous

Fig. 34.32

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Key

Articular Quadrate Dentary Squamosal

Biarmosuchus, a synapsid

Temporal fenestra

Jaw joint

(a) Articular and quadrate bones in the jaw

Eardrum Middle ear

Stapes Inner ear

Sound

Present-day reptile

(b) Articular and quadrate bones in the middle ear

Sound

Present-day mammal

Eardrum Middle ear

Inner ear

Stapes

Incus (quadrate)

Malleus (articular)

MammalsMonotremes - small group of egg-laying mammals (echidnas and platypus)Marsupials - opossums, kangaroos, and koalas

Born very early in its development In some the marsupium opens in the rear

(a) A young brushtail possum

(b) Long-nosed bandicoot

Plantigale

Marsupial mammals

Eutherian mammals

Marsupial mole

Sugar glider

Wombat

Tasmanian devil

Kangaroo

Deer mouse

Mole

Flying squirrel

Woodchuck

Wolverine

Patagonian cavy Figs. 34.38-34.40

MammalsEutherians - placental mammals

Have a longer period of pregnancy (compared to marsupials)Young eutherians complete their embryonic development within a uterus joined to the mother by a placenta

Fig. 34.41Monotremata

Orders and Examples Main Characteristics Orders and Examples Main Characteristics

Platypuses, echidnas

Echidna

Proboscidea Elephants

African elephant

Sirenia Manatees, dugongs

Manatee

Lay eggs; no nipples; young suck milk from fur of mother

Long, muscular trunk; thick, loose skin; upper incisors elongated as tusks

Aquatic; finlike fore- limbs and no hind limbs; herbivorous

Xenarthra Sloths, anteaters, armadillos

Tamandua

Lagomorpha Rabbits, hares, picas

Jackrabbit

Reduced teeth or no teeth; herbivorous (sloths) or carnivorous (anteaters, armadillos)

Chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping; herbivorous

Sharp, pointed canine teeth and molars for shearing; carnivorous

Hooves with an even number of toes on each foot; herbivorous

Aquatic; streamlined body; paddle-like fore-limbs and no hind limbs; thick layer of insulating blubber; carnivorous

Carnivora Dogs, wolves, bears, cats, weasels, otters, seals, walruses Coyote

Cetartiodactyla Artiodactyls Sheep, pigs, cattle, deer, giraffes

Cetaceans Whales, dolphins, porpoises

Marsupialia Kangaroos, opossums, koalas

Koala

Completes embryonic development in pouch on mother’s body

Tubulidentata Aardvarks

Aardvark

Teeth consisting of many thin tubes cemented together; eats ants and termites

Hyracoidea Hyraxes

Rock hyrax

Short legs; stumpy tail; herbivorous; complex, multi- chambered stomach

Rodentia Squirrels, beavers, rats, porcupines, mice Red squirrel

Chisel-like, continuously growing incisors worn down by gnawing; herbivorous

Primates Lemurs, monkeys, chimpanzees, gorillas, humans Golden lion

tamarin

Opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous

Perissodactyla Horses, zebras, tapirs, rhinoceroses

Indian rhinoceros

Hooves with an odd number of toes on each foot; herbivorous

Chiroptera Bats

Frog-eating bat

Eulipotyphla “Core insectivores”: some moles, some shrews

Star-nosed mole

Eat mainly insects and other small invertebrates

Adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous Bighorn sheep

Pacific white- sided porpoise

13

14

15

MammalsPrimates - include lemurs, tarsiers, monkeys, and apes

Hands and feet adapted for graspingLarge brain and short jawForward-looking eyes close together on the face providing depth perceptionWell-developed parental care and complex social behaviorOpposable thumbsOldest known anthropoid fossils are from about 45 million years ago

Fig. 34.43-34.44

ANCESTRAL PRIMATE

Time (millions of years ago) 60 50 40 30 20 10 0

Lemurs, lorises, and bush babies

Tarsiers

New World monkeys

Old World monkeys

Gibbons

Orangutans

Gorillas

Chimpanzees and bonobos

Humans

Anthropoids

(b) Old World monkey: macaque (a) New World monkey: spider monkey

Evolution of PrimatesNew and Old World monkeys underwent separate adaptive radiations during millions of years of separationThe other group of anthropoids are hominoids (consist of primates called apes)Hominoids diverged from Old World monkeys about 20-25 million years ago

Figs. 34.39-34.40

(a) Gibbon (b) Orangutan

(c) Gorilla

(d) Chimpanzees

(e) Bonobos

Derived Characters of HomininsBipedal hominoids with a large brainLanguage capabilitiesSymbolic thoughtManufacture and use of complex toolsShortened jawHumans and chimpanzee genomes are more than 99% identical

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

Mill

ions

of y

ears

ago

Australo- pithecus anamensis

Kenyanthropus platyops

Australopithecus africanus

Paranthropus boisei

Paranthropus robustus

Homo ergaster

Homo neanderthalensis

Homo sapiens

Homo erectus

Homo rudolfensis Homo

habilis

Australopithecus garhi

?

Australopithecus afarensis

Ardipithecus ramidus

Orrorin tugensis

Sahelanthropus tchadensis

Fig. 34.46

16

17

18

HominidsStudy of human origins is paleoanthropology20 species of distinct hominins have been discoveredOriginated in Africa 6-7 million years ago

Australopiths lived between 4 and 2 million years ago

Early hominids had a small brainTwo common misconceptions:

Often thought of as chimpanzeesThinking of human evolution as a ladder leading to Homo sapiens

Began to walk on two legs for long distances about 1.9 million years agoBegan to use tools (cut marks on animal bones) about 2.5 million years ago

Figs. 34.47 & 34.48

(a) The Laetoli footprints (b) Artist’s reconstruction of A. afarensis

HominidsHomo habilis - 2.4 to 1.6 million years ago

Stone tools have been found with themHomo ergaster - 1.9 to 1.6 million years ago

First fully bipedal, large brained hominidHomo erectus - about 1.8 million years ago

First hominid to leave AfricaHomo neanderthalensis - 200,000 to 30,000 years ago

Lived in Europe and the Near EastLarge, thick browedBecame extinct a few thousand years after Homo sapiens arrived in Europe

Homo sapiens - 160,000 years agoOldest fossils outside of Africa about 50,000 years ago

Figs. 34.49 & 34.50

19

20