10 Paleontology

8/6/2019 10 Paleontology

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Leyte Normal University

Tacloban City

Natural Science:PALEONTOLOGY

Prepared by:

Ma. Victoria D. Naboya


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History of paleontology

Duria Antiquior - A more

AncientDorsetis a

watercolor painted in 1830

by the geologistH

enry Dela Beche based on fossils

found by Mary Anning.

The late 18th and early

19th century was a time of

rapid and dramiticchanges in ideas about

the history of life on earth.


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PALEONTOLOGY The history ofpaleontology traces the effort to understand the history oflife on Earth by studying the fossil record left behind by living organisms.

Paleontology is a field of biology but its development has been closely tiedto geology and the effort to understand the history of Earth itself.

In Europe the systematic study of fossils emerged as an integral part of

the changes in natural philosophy that occurred during the Age of reason.

The nature of fossils and their relationship to life in the past became betterunderstood during the 17th and 18th centuries, and at the end of the 18thcentury the work ofGeorges Cuvierled to the emergence ofpaleontology,in association with comparative anatomy

, as a scientific discipline.

The expanding knowledge of the fossil record also played an increasingrole in the development ofgeology, particularly stratigraphy.


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PALEONTOLOGY The first half of the 19th century saw a rapid increase in

knowledge about the past history of life on Earth andprogress towards definition of the geologic time scale.

This made it increasingly obvious that there had beensome kind of successive order to the development oflife, and that would contribute to early theories of thetransmutation of species.

AfterCharles Darwin published Origin of Species in1859, much of the focus of paleontology shifted tounderstanding evolutionary paths, including humanevolution, and evolutionary theory.


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PALEONTOLOGY The last half of the 19th century saw a

tremendous expansion in paleontologicalactivity, especially in North America.

The trend continued in the 20th century withadditional regions of the Earth being opened tosystematic fossil collection, as demonstratedby a series of important discoveries in China.

The last half of the 20th century saw a renewedinterest in mass extinctions and their role inthe evolution of life on Earth.


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Prior to the 17th century

As early as the 6th century BC, Xenophanes ofColophon recognized that some fossil shells wereremains of shellfish, which he used to argue that whatwas at the time dry land was once under the sea.

Leonardo da Vinci (1452-1519), in an unpublishednotebook, also concluded that some fossil sea shellswere the remains of shellfish.

However, in both cases, the fossils were completeremains of shellfish species that closely resembledliving species, and were therefore easy to classify.


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Shen Kuo (Chinese:) (1031 - 1095) of the SongDynasty used the evidence ofmarine fossils found inthe Taihang Mountains to infer the existence ofgeological processes ofgeomorphology and shifting

of seashores over time.

Using his observation of preserved petrifiedbamboos found underground inYan'an, Shanbeiregion, Shaanxi province, he argued for a theory ofgradual climate change, since Shaanxi was (and stillis) part of a dry climate zone that does not support ahabitat for the growth of bamboos.


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However, most 16th century Europeans did notrecognize that fossils were the remains of livingorganisms.

The etymology of the word fossil comes from the Latinfor things having been dug up. As this indicates, theterm was applied to wide variety of stone and stone-likeobjects without regard to whether they might have anorganic origin.

Sixteenth century writers such as Conrad GesnerandGeorg Agricola were more interested in classifying suchobjects by their physical and mystical properties thanthey were in determining the objects' origins.


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The natural philosophy of the period encouragedalternative explanations for the origin of fossils. Boththe Aristotelian and Neoplatonic schools of philosophyprovided support for the idea that stony objects mightgrow within the earth to resemble living things.

Neoplatonic philosophy maintained that there could beaffinities between living and non-living objects thatcould cause one to resemble the other.

The Aristotelian school maintained that the seeds ofliving organisms could enter the ground and generateobjects resembling those organisms.


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17th century

During the Age of Reason, fundamental changes in naturalphilosophy were reflected in the analysis of fossils.

In 1665 Robert Hooke published Micrographia, an illustratedcollection of his observations with a microscope.

One of these observations was entitled

Of Petrify'd wood, andother Petrify'd bodies, which included a comparison between

petrified and ordinary wood.

He concluded that petrified wood was ordinary wood that had beensoaked with "water impregnated with stony and earthy particles".

He then suggested that several kinds of fossil sea shells wereformed from ordinary shells by a similar process.

He argued against the prevalent view that such objects were"Stones form'd by some extraordinary Plastick virtue latent in theEarth itself".


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17th century In 1667 Nicholas Steno wrote a paper comparing the teeth of the

shark with the common fossil objects known as tongue stones.

He concluded that the fossils must have been shark teeth. Stenothen took an interest in the question of fossils and to address someof the objections to their ancient organic origin.

This work was published in 1669 as

Forerunner to a Dissertation ona solid naturally enclosed in a solid. In this book, Steno drew a clear

distinction between objects such as rock crystals that really wereformed within rocks and those such as fossil shells and shark teeththat were formed outside of those rocks.

Steno realized that certain kinds of rock had been formed by thesuccessive deposition of horizontal layers of sediment and thatfossils were the remains of living organisms that had becomeburied in that sediment.

Steno who, like almost all 17th century natural philosophers,believed that the earth was only a few thousand years old, resorted

to the Biblical flood as a possible explanation for fossils of marineorganism that were found very far from the sea.


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17th century

Despite the considerable influence ofForerunner,naturalists such as Martin Lister(1638-1712) andJohn Ray (1627-1705) continued to question theorganic origin of some fossils.

They were particularly concerned about objects suchas fossil Ammonites, which Hooke had claimed wereorganic in origin, that did not resemble any knownliving species.

This raised the possibility ofextinction, which theyfound difficult to accept for philosophical andtheological reasons.


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18th century

This illustration of an Indian

elephant jaw and amammoth jaw is from

Cuvier's 1796 paper on living

and fossil elephants.


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18th century

In his 1778 work Epochs of Nature

Georges Buffon referred to fossils, in

particular the discovery of fossils of

tropical species such as elephants and

rhinoceros in northern Europe, as

evidence for the theory that the earth

had started out much warmer than itcurrently was and had been gradually

cooling.


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18th century In 1796 Georges Cuvierpresented a paper on living and

fossil elephants comparing skeletal remains of Indianand African elephants to fossils ofmammoths and of ananimal he would later name mastodon utilizingcomparative anatomy.

He established for the first time that Indian and Africanelephants were different species, and that mammoths

differed from both and must be extinct. He furtherconcluded that the mastodon was another extinctspecies that also differed from Indian or Africanelephants, more so than mammoths.

Cuviers ground-breaking work in paleontology andcomparative anatomy lead to the widespreadacceptance of extinction.


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18th century

It also lead Cuvier to advocate the geological theory ofcatastrophism to explain the succession of organismsrevealed by the fossil record.

He also pointed out that since mammoths and woolyrhinoceros were not the same species as the

elephants and rhinoceros currently living in thetropics, their fossils could not be used as evidence fora cooling earth.

Cuvier made another powerful demonstration of the

power of comparative anatomy in paleontology whenhe presented a second paper in 1796 on a large fossilskeleton from Paraguay, which he namedMegatherium and identified as a giant sloth bycomparing its skull to those of two living species oftree sloth.


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18th century

This

illustration is

from William

Smith's 1815

work Strata by

OrganizedFossils.


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18th century In a pioneering application ofstratigraphy, William Smith, a

surveyor and mining engineer, made extensive use of fossils tohelp correlate rock strata in different locations.

He created the first geological map of England during the late 1790sand early 1800s.

He established the principle of faunal succession, the idea that eachstrata of sedimentary rock would contain particular types of fossils,

and that these would succeed one another in a predictable wayeven in widely separated geologic formations.

At the same time, Cuvier and Alexandre Brongniart, an instructor atthe Paris school of mine engineering, used similar methods in an

influential study of the geology of the region around Paris.


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First half of the 19th century

This illustration of

fossil Iguanodon teeth

with a modern iguana

jaw for comparison is

from Mantell's 1825

paper describing

Iguanodon.


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The age of reptiles

In 1808, Cuvier identified a fossil found inMaastricht as a giant marine reptile that

he named Mosasaurus.

He also identified, from a drawing,

another fossil found in Bavaria as a flying

reptile and named it Pterodactylus.

He speculated that an age of reptiles had

preceded the first mammals.


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The age of reptiles

In 1824, Buckland found and described a lower jaw fromJurassicdeposits from Stonesfield.

He determined that the bone belonged to a carnivorous land-dwellingreptile he called Megalosaurus.

That same yearGideon Mantell realized that some large teeth he hadfound in 1822, in Cretaceous rocks from Tilgate, belonged to a giantherbivorous land-dwelling reptile.He called it Iguanodon, becausethe teeth resembled those of an iguana.

In 1832 Mantell would find, in Tilgate, a partial skeleton of anarmoured reptile he would callHylaeosaurus.

In 1842 the English anatomist Richard Owen would create a neworder of reptiles, that he called Dinosauria forMegalosaurus,Iguanodon and Hylaeosaurus.


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The age of reptiles

This illustration of

the fossil jaw of theStonesfield mammal

is from Gideon

Mantell's 1848 book

Wonders of

Geology.


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The age of reptiles This evidence that giant reptiles had lived on Earth in

the past caused great excitement in scientific circles,and even among some segments of the general public.

Buckland did describe the jaw of a small primitivemammal, Phascolotherium, that was found in the same

strata as Megalosaurus. This discovery, known as theStonesfield mammal, was a much discussed anomaly.Cuvier at first thought it was a marsupial, but Bucklandlater realized it was a primitive placental mammal.

Due to its small size and primitive nature, Buckland didnot believe it invalidated the overall pattern of a timenamed "the age of reptiles", when the largest and mostconspicuous animals had been reptiles rather thanmammals.


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Paleobotany In 1828 Alexandre Brongniart's son, the botanist Adolphe Brongniart, published the

introduction to a longer work on the history of fossil plants.

Adolphe Brongniart concluded that the history of plants could roughly be dividedinto four parts.

The first period was characterized by cryptogams.

The second period was characterized by the appearance of the conifers.

The third period brought emergence of the cycads, and

The forth by the development of the flowering plants (such as the dicotyledons).

The transitions between each of these periods was marked by sharp discontinuitiesin the fossil record, with gradual changes within clades of plants.

Brongniart's work is the foundation ofpaleobotany and reinforced the theory thatlife on earth had a long and complex history, and different groups of plants andanimals made their appearances in successive order.


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Catastrophism, uniformitarianism

and the fossil record Partly in response to what he saw as unsound and unscientific speculations by

William Buckland and other practitioners of flood geology,

Charles Lyell advocated the geological theory ofuniformitarianism in hisinfluential work Principles of Geology.

Lyell amassed evidence, both from his own field research and the work ofothers, that most geological features could be explained by the slow action ofpresent day forces, such as vulcanism, earthquakes, erosion, andsedimentation rather than past catastrophic events.

Lyell also claimed that the apparent evidence for catastrophic changes in thefossil record, and even the appearance of directional succession in the historyof life, were illusions caused by imperfections in that record. For instance he

argued that the absence of birds and mammals from the earliest fossil stratawas merely an imperfection in the fossil record attributable to the fact thatmarine organisms were more easily fossilized.


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and the fossil record

As evidence for these views Lyell pointed to the Stonesfieldmammal as evidence that mammals had not necessarily beenpreceded by reptiles, and to the fact that certain Pleistocenestrata showed a mixture of extinct and still surviving species,which he said showed that extinction occurred piecemeal ratherthan as a result of catastrophic events

Lyell was successful in convincing geologists of the idea that thegeological features of the earth were largely due to the action ofthe same geologic forces that could be observed in the presentday, acting over an extended period of time.

e was not successful in gaining support for his view of the fossilrecord, which he believed did not support a theory of directionalsuccession.


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and the fossil record

In Cuvier's landmark 1796 paper on living and fossil elephants, he referred to asingle catastrophe that destroyed life to be replaced by the current forms.

As a result of his studies of extinct mammals, he realized that animals such asPalaeotherium had lived before the time of the Mammoths, which lead him towrite in terms of multiple geological catastrophes that had wiped out a seriesof successive faunas.

By 1830, a scientific consensus had formed around his ideas as a result ofpaleobotany and the dinosaur and marine reptile discoveries in Britain.

In Great Britain, where natural theology was very influential in the early 19thcentury, a group of geologists that included Buckland, and

Robert Jameson insisted on explicitly linking the most recent of Cuvier'scatastrophes to the biblical flood. Catastrophism had a religious overtone inBritain that was absent elsewhere.


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Transmutation of species and the

fossil record Jean Baptiste Lamarck used fossils in his arguments for his theory

of the transmutation of species in the early 19th century. Fossilfinds, and the emerging evidence that life had changed over time,fueled speculation on this topic during the next few decades.

Robert Chambers used fossil evidence in his 1844 popular sciencebook Vestiges of the Natural History of Creation, which advocatedan evolutionary origin for the cosmos as well as for life on earth.Like Lamarck's theory it maintained that life had progressed fromthes simple to the complex.

These early evolutionary ideas were widely discussed in scientificcircles but were not accepted into the scientific mainstream. Manyof the critics of transmutational ideas used fossil evidence in therearguments.


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Transmutation of species and the

fossil record In the same paper that coined the term dinosaur

Richard Owen pointed out that dinosaurs were at leastas sophisticated and complex as modern reptiles, whichhe claimed contradicted transmutational theories.

Hugh Millerwould make a similiar argument, pointingout that the fossil fish found in the Old Red Sandstoneformation were fully as complex as any later fish, andnot the primitive forms alleged by Vestiges.

While these early evolutionary theories failed to becomeaccepted as mainstream science, the debates over themwould help pave the way for the acceptance of Darwin's

theory of evoluton by natural selection a few years later.


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Geological time scale and the history of

life

Geologists such as Adam Sedgwick, and Roderick Murchison continued,despite disputes with other scientists, to make advances in stratigraphy.They described new geological epochs such as the Cambrian, the Silurian,the Devonian, and the Permian.

By the early 1840s much of the geologic time scale had been developed. In1841, John Phillips formally divided the geologic column into three major

eras, the Paleozoic, Mesozoic, and Cenozoic, based on sharp breaks in thefossil record.

He identified the three periods of the Mesozoic era and all the periods ofthe Paleozoic era except the Ordovician. His identification of the geologicaltime scale is still used today.

It remained a relative time scale with no method of assigning any of theperiods' absolute dates. It was understood that not only had there been an"age of reptiles" preceding the current "age of mammals", but there had atime (during the Cambrian and the Silurian) when life had been restricted tothe sea, and a time (prior to the Devonian) when invertebrates had been thelargest and most complex forms of animal life.


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Expansion and professionalization

of geology and paleontology

This rapid progress in geology and paleontologyduring the 1830s and 1840s was aided by a growinginternational network of geologists and fossilspecialists whose work was organized and reviewed

by an increasing number of geological societies.

Many of these geologists and paleontolgists were nowpaid professionals working for universities, museumsand government geological surveys. The relatively

high level of public support for the earth sciences wasdue to their cultural impact, and their proveneconomic value in helping to exploit mineralresources such as coal.


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2nd half of the 19th century

Charles Darwin's publication of the Origin of Species in 1859 was awatershed event in all the life sciences, especially paleontology.

Fossils had played a role in the development of Darwin's theory. In particularhe had been impressed by fossils he had collected in South America duringthe voyage of the Beagle ofgiant armadillos, giant sloths, and what at thetime he thought were giant llamas that seemed to be related to species stillliving on the continent in modern times.

The scientific debate that started immediately after the publication ofOriginled to a concerted effort to look fortransitional fossils and other evidence ofevolution in the fossil record. There were two areas where early successattracted considerable public attention, the transition between reptiles andbirds, and the evolution of the modern single-toed horse.

In 1861 the first specimen ofArchaeopteryx, an animal with both teeth andfeathers and a mix of other reptilianand avian features, was discovered in alimestone quarry in Bavaria and described by Richard Owen.


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2nd half of the 19th century

Another would be found in the late 1870s and put on display at aMuseum in Berlin in 1881. Other primitive toothed birds were foundby Othniel Marsh in Kansas in 1872. Marsh also discovered fossilsof several primitive horses in the WesternUnited States that helpedtrace the evolution of the horse from the small 5-toedHyracotherium of the Eocene to the much larger single-toed modern

horses of the genusEquus.

Thomas Huxley would make extensive use of both the horse andbird fossils in his advocacy of evolution. Acceptance of evolutionoccurred rapidly in scientific circles, but acceptance of Darwin'sproposed mechanism ofnatural selection as the driving force

behind it was much less universal. In particular somepaleontologists such as Edward Drinker Cope and Henry FairfieldOsborn preferred alternatives such as neo-Lamarckism, theinheritance of characteristics acquired during life, andorthogenesis, an innate drive to change in a particular direction, toexplain what they perceived as linear trends in evolution.


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Evolution

There was also great interest in humanevolution. Neanderthal fossils werediscovered in 1856, but at the time it wasnot clear that they represented a differentspecies from modern humans.

Eugene Dubois created a sensation with

his discovery ofJava Man, the first fossilevidence of a species that seemed clearlyintermediate between humans and apes,in 1891.


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Developments in North America

A major development in the 2nd half of the19th century was a rapid expansion ofpaleontology in North America.

In 1858 Joseph Leidy described aHadrosaurus skeleton, which was the firstNorth American dinosaur to be describedfrom good remains. However, it was themassive westward expansion of railroads,military bases, and settlements into Kansasand other parts of the Western United Statesfollowing the American Civil Warthat reallyfueled the expansion of fossil collection.


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Developments in North America

The result was an increased understanding ofthe natural history of north America, includingthe discovery of the Western Interior Sea thathad covered Kansas and much of the rest ofthe Midwestern United States during parts ofthe Cretaceous, the discovery severalimportant fossils of primitive birds and horses,and the discovery of a number of new dinosaurspecies includingAllosaurus, Stegosaurus,and Triceratops. Much of this activity was partof a fierce personal and professional rivalrybetween two men, Othniel Marsh, and EdwardCope, which has become known as the BoneWars.


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Overview of developments in the 20th

century

Developments in geology

Two 20th century developments in geology had abig effect on paleontology.

The first was the development ofradiometricdating, which allowed absolute dates to beassigned to the geologic timescale.

The second was the theory ofplate tectonics,which helped make sense of the geographicaldistribution of ancient life.


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Overview of developments in the 20th

century

Geographical expansion of paleontology

During the 20th century paleontological exploration intensifiedeverywhere and ceased to be a largely European and NorthAmerican activity.

In the 135 years between Buckland's first discovery and 1969 atotal of 170 dinosaur genera were known. In the 25 years after 1969that number increased to 315. Much of this increase was due to theexamination of new rock exposures, particularly in previously little-explored areas in South America and Africa.

Near the end of the century the opening ofChina to systematicexploration for fossils has yielded a wealth of material ondinosaurs and the origin of birds and mammals.


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Mass extinctions The 20th century saw a major renewal of interest in

mass extinction events and their effect on the course ofthe history of life.

This was particularly true after 1980 when Luis andWalter Alvarez put forward the Alvarez hypothesis

claiming that an impact event caused the Cretaceous-Tertiary extinction, which killed off the non-aviandinosaurs along with many other living things.

Also in the early 1980's Jack Sepkoski and David M.Raup published papers with statistical analysis of thefossil record of marine invertebrates that revealed apattern (possibly cyclical) of repeated mass extinctionswith significant implications for the evolutionary historyof life.


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Evolutionary paths and theory

Other events that have attracted considerableattention have included the discovery of aseries of fossils in Pakistan that have shed lighton whale evolution, and most famously of all aseries of finds throughout the 20th century inAfrica (starting with Taung child in 1924) andelsewhere have helped illuminate the course ofhuman evolution.

Increasingly, at the end of the century, theresults of paleontology and molecular biologywere being brought together to reveal detailed

phylogenetic trees.


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Cambrian explosion One area of paleontology that has seen a lot of activity during the

1980s, 1990s and beyond is the study of the Cambrian explosionduring which many of the various phyla of animals with theirdistinctive body plans first appear.

The well-known Burgess Shale Cambrian fossil site was found in1909 by Charles Doolittle Walcott, and another important site inChengjiang China was found in 1912.

However, new analysis in the 1980s byHarry B. Whittington, DerekBriggs, Simon Conway Morris and others sparked a renewedinterest and a burst of activity including discovery of an importantnew fossil site, Sirius Passet, in Greenland, and the publication ofa popular and controversial book, Wonderful Life by Stephen Jay

Gould in 1989.

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10 Paleontology