Professor John KricherWHEATON COLLEGE

BEHOLD THE

MIGHTY

DINOSAURCOURSE GUIDE

Behold the Mighty DinosaurProfessor John Kricher

Wheaton College

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Behold the Mighty DinosaurProfessor John Kricher

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Course Syllabus

Behold the Mighty Dinosaur

About Your Professor/Introduction ...............................................................................4

Lecture 1 What Is (or Was) a Dinosaur? ...............................................................6

Lecture 2 Digging Up Dinos...................................................................................9

Lecture 3 Dinosaurs Discovered..........................................................................12

Lecture 4 The Bone Wars....................................................................................16

Lecture 5 The Museum That Dinosaurs Built ......................................................19

Lecture 6 Dinosaurs Enter Pop Culture...............................................................23

Lecture 7 Dinosaur Origins ..................................................................................27

Lecture 8 In the Days of Dinosaurs .....................................................................31

Lecture 9 Dinosaur Diversity................................................................................35

Lecture 10 Dinosaurs Become Dynamic ...............................................................39

Lecture 11 Dinosaurs Become Airborne................................................................43

Lecture 12 Dinosaurs as Living Animals ...............................................................48

Lecture 13 T. REX Deconstructed and Reconstructed ...........................................52

Lecture 14 The Cretaceous Extinction Event ........................................................57

Course Materials ........................................................................................................62

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John Kricher is a professor of biologyat Wheaton College, Norton, Massachu -setts. His books include Galapagos: ANatural History, A NeotropicalCompanion, three ecology field guides(Eastern Forests; Rocky Mountain andSouthwestern Forests; and Californiaand Pacific Northwest Forests), andFirst Guide to Dinosaurs. John is a fel-low in the American Ornithologists

Union and past-president of both the Association of Field Ornithologists andWilson Ornithological Society. His interest in dinosaurs has taken him to vir-tually all of the major museum collections and he has “hunted dinosaurs” inConnecticut, Colorado, Utah, Wyoming, Montana, and along the Red DeerRiver in Alberta. He teaches about dinosaurs in his classes and he hasamassed a large private collection of dinosaur models. He resides with hiswife Martha Vaughan on Cape Cod.

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About Your Professor

John Kricher

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IntroductionDinosaurs—the word means “fearfully great reptile”—have been a source of

fascination ever since their discovery in England early in the nineteenth cen-tury. No human ever has or ever will see a live long-necked APATOSAURUS, theodd-plated STEGOSAURUS, or the infamous TYRANNOSAURUS REX, yet commonbirds such as cardinals and chickadees trace their ancestries back todinosaurs. Dinosaurs, once believed to be immense behemoths, dull of mind,slow of body, mired in swamps like so many oversized sluggish lizards, havereawakened interest, and research on dinosaurs has burgeoned.

Dinosaurs present the ultimate puzzle in forensic science. They excite ourcuriosity, even our awe. Aside from birds, all dinosaurs have been extinct for65 million years, yet, before then, they dominated Earth’s terrestrial habitatsfor about 160 million years, far longer than primates, to say nothing ofhumans, have been around. We have evidence of their existence and even of their former lives, evidence in the form of bones, skulls, whole skeletons,skin, trackways, eggs, nests, even feces. The puzzles about dinosaurs arecomplex, but nonetheless we have learned a great deal about them, especial-ly in the last fifty years. Our view of dinosaurs has changed radically, and theevolution and biology of dinosaurs has become a popular topic in college cur-riculums. This lecture series will explain how this changing view of dinosaursdeveloped and what it means to evolutionary biology.

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Beginning with the discovery and initial interpretation of dinosaurs, we willcome to understand why these unique animals were initially thought to belarge lizards but were soon realized to be in a group of their own. We willlearn of the great finds of the late-nineteenth and early-twentieth centuriesand the infamous “bone wars” fought between two driven geniuses to estab-lish supremacy as dinosaur collectors. We will follow the great dinosaur collectors through the American West and on to Mongolia in search of fossil bones. The American Museum of Natural History in New York Citynow houses the greatest collection of dinosaur skeletons, largely because itwas recognized early in the twentieth century that dinosaurs interest thepublic and people will come to museums to see their remains.

Since their discovery, dinosaurs have been part of pop culture. Books andfilms have featured and celebrated dinosaurs. Professor Kricher will detailhow dinosaur pop culture has evolved, including the great interest generatedby the release of the film Jurassic Park in 1993, soon followed by the highlyacclaimed BBC series Walking with Dinosaurs.

In the mid-1960s scientists began to view dinosaurs differently. Evidencemounted, largely thanks to two paleontologists from Yale University, JohnOstrom and Robert Bakker, that dinosaurs were warm-blooded and active,more like mammals and birds than like reptiles. At about the same time newattention was given to the old notion that birds evolved from dinosaurs. Fieldand lab studies burgeoned and Professor Kricher will discuss how the“Dinosaur Renaissance” was achieved and how it resulted in a great rush ofnew dinosaur exploration, excavation, research, and interpretation. Neverhave dinosaurs been more a focus of science than they are today.

The lectures will explain evolutionary and ecological relationships amongdinosaurs and provide the listener with a sense of what it might have beenlike to be present in the Mesozoic Era during the time of the dinosaurs. Onelecture will be devoted entirely to questions surrounding TYRANNOSAURUS REX

and the final lecture will deal with the question of what ultimately broughtabout the total extinction of all of the non-bird dinosaurs.

poem written less than a century after the discovery ofdinosaurs begins with the line, “Behold the mighty dinosaur,famous in prehistoric lore.” Dinosaurs, a name that trans-

lates to “fearfully great reptile” (sometimes interpreted as“terrible lizard”), have excited the public mind ever sincetheir discovery in the early nineteenth century. Theyhave been portrayed as immense in size, bizarre inappearance, stupid of mind, impressively dangerous,and, of course, totally extinct. Indeed, the name

“dinosaur” is sometimes applied to anything or anyone perceived to have out-lived its usefulness. Dinosaurs have become icons of failure, the poster chil-dren for extinction. At the same time, they continue to fascinate. And thanksto advances in computer animation, films such as Jurassic Park and the BBCseries Walking with Dinosaurs virtually re-create these wondrous creatures ofthe Mesozoic Era.

Were dinosaurs evolutionary failures? I say an emphatic “No!” and this lec-ture series will hopefully convince you that dinosaurs were and, in the form ofbirds, continue to be one of the most diverse and successful groups of back-boned animals.

The poem The Riddle of the Dinosaur captures the mystique of theseremarkable animals. It is about a dinosaur named STEGOSAURUS, a creaturemost children could identify. Bigger than the largest rhino, its back lined withformidable bony plates, and a tail armed with four menacing bony spikes, thisanimal is easily recognized. Add to that countenance its tiny head containinga walnut-sized brain and you have the enigma of the dinosaur: large, bizarre,stupid. STEGOSAURUS had a swelling in its vertebral column at its hips, indicat-ing that its spinal cord was unusually thick in that region. This reality gaverise to the fanciful notion that “the creature had two sets of brains,” the topicof the poem.

Dinosaurs are among the only animals we know by their scientific ratherthan common names. We don’t call it “roofed lizard,” we call it STEGOSAURUS.We refer to ALLOSAURUS and ANATOTITAN, rather than “other lizard” and “bigduck.” Some dinosaurs have even been named more than once. Thedinosaur APATOSAURUS (meaning “deceptive lizard”) was once calledBRONTOSAURUS, a great name that translates to “thunder lizard.” But, alas, abundle of bones was named APATOSAURUS before another bundle of bonesfrom a different individual of the same species was named BRONTOSAURUS, soAPATOSAURUS is the official scientific name. Perhaps the finest dinosaur nameof them all is TYRANNOSAURUS REX, the “king of tyrant lizards.”

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The Suggested Reading for this lecture is John Noble Wilford’s TheRiddle of the Dinosaur.

Lecture 1:What Is (or Was) a Dinosaur?

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Many dinosaurs were large, even huge, bigger than any other land animalsto have ever existed. Some of the largest weighed in excess of fifty tons. Butmany were comparable in size to some of today’s mammals, such as ele-phants, rhinos, and hippos. Some were rather small and some only the sizeof chickens, weighing less than house cats. Many were indeed bizarre inappearance and certainly many would be dangerous were they still roamingthe wilds today. And, yes, many were dumb, even by crocodile standards.But not all were.

Are dinosaurs extinct? Their time, the Mesozoic Era, ended abruptly sixty-five million years ago. Gone were the likes of T. REX and TRICERATOPS, per-haps done in by the effects of a ten-kilometer asteroid striking the Earth. Butas these lectures will make clear, birds evolved from a lineage of dinosaurs.Birds survived the big extinction event and thus only the so-called “non-aviandinosaurs” became extinct. One group of dinosaurs survived, the birds, andtoday nearly ten thousand feathered dinosaurs, more than twice the numberof mammal species, share our world.

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Behold the mighty dinosaur,

Famous in prehistoric lore,

Not only for his power and strength

But for his intellectual length.

You will observe by these remains

The creature had two sets of brains—

One in his head (the usual place),

The other at his spinal base.

Thus he could reason ‘A Priori’

As well as ‘A Posteriori.’

No problem bothered him a bit

He made a head and tail of it.

So wise was he, so wiseand solemn,

The Riddle of the Dinosaurby Bert Leston Taylor

(1866—1921)

Each thought filled just one spinal column.

If one brain found the pressure strong

It passed a few ideas along.

If something slipped his forward mind

’Twas rescued by the one behind

And if an error he was caught

He had a saving afterthought.

As he thought twice before he spoke

He had no judgment to revoke.

Thus he could think without congestion.

Upon both sides of the question.

Oh, gaze upon this model beast,

Defunct ten million years at least.

Source: The Edgar Rice Burroughs Library; http://www.erbzine.com/dan/t1.html

© Clipart.com

1. Why are dinosaurs often viewed as “evolutionary failures”?

2. Why is this view not accurate?

Wilford, John Noble. The Riddle of the Dinosaur. New York: Alfred A.Knopf, 1985.

de Camp, L. Sprague, and Catherine Cook de Camp. The Day of theDinosaur. New York: Doubleday & Company, 1968.

The Dinosaur Corporation website Dinosaur Timeline Gallery features a col-lection of dinosaur and prehistoric illustrations by paleo-artist Josef Moravecalong with short overviews of the different periods in Earth’s history —http://www.prehistory.com/colorchr.htm

Websites to Visit

�Questions

Suggested Reading

FOR GREATER UNDERSTANDING

Other Books of Interest

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inosaurs first evolved in the Mesozoic Era about 230 million years ago and they did not become extinct untilsixty-five million years ago (and even then, they weresurvived by the birds). So the non-avian dinosaursenjoyed a long tenure on Earth, about 165 millionyears, far longer than humans or their immediate

ancestors have been present on the planet. That spanof time seems like a lot, ample time to accumulate many

dinosaur corpses. But it’s not that simple. The world is not lit-tered with dead bodies of animals because they are scavenged, torn apart,rotted, and totally decomposed, ultimately by bacteria. So it is now, so it wasin the days of dinosaurs.

Fossils are relatively rare. The chance of any animal becoming fossilized isminiscule. The chances of hitting the fossil jackpot, becoming the one T. REX

that is perfectly preserved down to the last little bone, is likely less probablethan winning a huge lottery jackpot. But given lots of time and lots ofdinosaurs, there are winners. We have a fossil record to draw upon.

The fossil record is the dinosaur database. And excavating these long-deadcreatures and then reconstructing how they looked in life and how they livedpresents the ultimate in forensic science.

Like all creatures, dinosaurs died of illness and infection, predation, injury,accidents, or, rarely, old age. When a dinosaur died it was likely to be con-sumed by a predator or scavengers and they would scatter its bones. Rarelyare complete skeletons found. If the corpse was not immediately dismem-bered it would bloat from intestinal bacterial gasses, maybe even rupture.Many dinosaur remains are found with their necks arching well over theirbacks, a posture called the “death pose.”

Hard parts such as teeth and bones tend to decompose slowly simplybecause they are mostly mineral and thus not nutritious to decomposerorganisms. Teeth, particularly enamel, are the hardest part of a vertebrateanimal, because they comprise mostly minerals of phosphorus and calcium.Soft parts are readily consumed and thus are rarely preserved.

Sometimes dinosaur skin, at least parts of it, are fossilized. In addition, suchthings as dinosaur eggs and nests, tracks and trackways, and feces some-times fossilize. All of these things are intensively studied.

An artifact must be at least ten thousand years old to be considered a fossiland thus all dinosaur remains are fossils. In most cases the original bone hasbeen replaced by other minerals, the process called petrification. Dinosaur

The Suggested Reading for this lecture is John R. Horner’sDigging Dinosaurs.

Lecture 2:Digging Up Dinos

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fossils are found only in sedimentary rocks, such as sandstone, mudstone,limestone, and shale. This is because they must be buried in some sort ofsediment for preservation to occur. Dinosaur fossils are aged by two meth-ods, biostratigraphy and radiometric dating. Only the latter method givesexact dates.

To find dinosaur fossils requires going to where sedimentary rocks ofMesozoic age are exposed. Such areas include the huge Morrison Formationof the American West, the Dinosaur Park Formation in Alberta, Canada, andplaces as wide ranging as Mongolia, eastern China, Argentina, southeasternAustralia, and Ethiopia. Even Alaska and Antarctica have dinosaur remains.Sometimes dinosaur bones are highly concentrated, such as at Howe Quarryin Big Horn Basin, Wyoming, where thirty metric tons of bone were removedin 1932, all destined for the American Museum of Natural History.

It requires skill to find dinosaur bones and skeletons. The untrained observereasily overlooks a piece of femur or a tooth, or a portion of a rib that may bejust slightly exposed.

It is a major task to excavate dinosaur skeletons. Sometimes the rock is veryhard and the skeleton deeply buried. As bones are exposed they are treatedto harden them, as they are often brittle. They are jacketed in plaster andburlap and carefully removed for transport to a museum. There the bonesmay be stored or immediately studied, meticulously exposed from the rock inwhich they are encased, and sometimes mounted for exhibition. Most skele-tons on exhibit these days are lightweight casts, identical to the “real thing”but easier to mount in lifelike postures.

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1. What is a fossil and what are some of the ways it can form?

2. How are dinosaur and other fossils aged?

Horner, John R. Digging Dinosaurs. New York: Workman Publishing, 1988.

Horner, John R. Dinosaurs Under the Big Sky. Missoula, MT: MountainPress, 2001.

Novacek, Michael. Dinosaurs of the Flaming Cliffs. New York: Doubleday, 1996.

The BBC Science and Nature website Age of Dinosaurs provides an exten-sive look at dinosaurs — http://www.bbc.co.uk/sn/prehistoric_life/dinosaurs

Websites to Visit

�Questions

Suggested Reading

FOR GREATER UNDERSTANDING

Other Books of Interest

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ossils of large extinct animals must have been found byhumans for as long as there have been humans. Thequestion, of course, was what these odd things were.Perhaps they were giant humans from ages past or per-haps mythological creatures such as griffins or cyclops.

The first actual description of a dinosaur bone was done byRobert Plot in England in 1677. But he thought the lower end ofthe thigh bone, which is all he had to go on, was that of a giant

human from biblical times. This analysis did not improve in accuracy whensome eighty-six years later the same exact specimen was rediscovered byRichard Brookes, who (because only the two rounded condyles of the base ofthe bone were preserved) took it to be a petrified scrotum from a giant humanmale. Thus Brookes named it Scrotum humanum, a poor choice of name forwhat was, in fact, the femur of a dinosaur, a MEGALOSAURUS. Fortunately, thename was never adopted.

Comparative anatomy was the discovery of Baron Georges Cuvier ofFrance, whose productive life spanned the turn of the eighteenth into thenineteenth century. He became so skilled at the study of vertebrate anatomythat he could generally identify any animal merely by looking at a single bonefrom it. Cuvier also provided scientific proof of the reality of extinction. Heargued that lineages of creatures suffered periodic catastrophes that annihi-lated many of them, but that newly created forms were improved over thosethat preceded them. This notion paralleled the concept of industrial and soci-etal progress and so was referred to as progressionism.

Fossils became curiosities not only to scientists, but to the general public. InEngland, Mary Anning of Dorset found and sold hundreds of fossils, includingwonderful specimens of ICHTHYOSAURS and PLESIOSAURS. She became highlycelebrated in the rhyme “She sells seashells by the seashore.” In the UnitedStates, a Massachusetts farm boy named Pliny Moody discovered many fos-silized tracks that appeared to be those of giant extinct birds, popularly called“Noah’s raven.” It would be years before it was realized that the tracks werethose made by dinosaurs over two hundred million years ago.

In England, William Buckland, in 1818, was shown the partial jawbone andteeth of what appeared to be a very large lizard. He named it MEGALOSAURUS,“large reptile.” Buckland did not know it at the time, but he had formallynamed the first dinosaur. Buckland believed that this reptile, whatever it was,was colossal. He estimated its length at about sixty to seventy feet, a signifi-cant overestimate.

The Suggested Reading for this lecture is Christopher McGowan’sThe Dragon Seekers: The Discovery of Dinosaurs During the Preludeto Darwin.

Lecture 3:Dinosaurs Discovered

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The second dinosaur to be described was discovered in 1825 by a physiciannamed Gideon Algernon Mantell. Originally based on fossil teeth and later onsome bones, Mantell believed the teeth of this extinct reptile bore a com-pelling resemblance to those of an iguana lizard, only much larger. Thus henamed his fossil IGUANODON, meaning “iguana tooth.”

Other fossil reptiles were found and it fell to a talented young anatomistnamed Richard Owen to formally analyze and describe the group. He did soand, in 1841, he presented his findings.

Owen asserted that the large extinct reptiles were unique, deserving of agroup of their own. He called this group DINOSAURIA, the “fearfully great rep-tiles.” Dinosaurs, as Owen defined them, were reptilian, large, upright in pos-ture, and had a backbone such that more than two sacral vertebrae articulat-ed with the hip.

Though Owen had no complete skeletons from which to work, he recon-structed dinosaurs to be rhinoceros-like, four-legged, stocky, but with a reptil-ian countenance. They had large thick tails that dragged behind them. Theirpillar-like legs ended in clawed feet. They were scaly, like lizards. Owenreconstructed IGUANODON with a nose horn similar to that of a rhinoceros.

When Great Britain celebrated the Great Exhibition of 1851, dinosaurs werefeatured in the form of full-scale models commissioned by Owen and sculptedby Waterhouse Hawkins. These models were striking, indeed impressive, butanatomically far from the mark. They can still be seen today in a park insouth London.

In 1858, Joseph Leidy found the first complete dinosaur skeleton inHaddonfield, New Jersey. He named it HADROSAURUS. He saw that its hindlegs were considerably larger than its fore legs and thus thought it musthave been bipedal. He reconstructed it standing upright on its hind legs, itslong tail dragging behind, its forelegs dangling in the air. It resembled a hugereptilian kangaroo.

The next complete dinosaur skeletons changed the image that Owen hadcreated of IGUANODON. In 1877, a huge deposit of IGUANODON skeletons wasfound in a coal mine in Bernissart, Belgium. Many skeletons were completeand thirty-nine were carefully removed for study and display in a Brusselsmuseum. Louis Dollo, an evolutionist and anatomist, reconstructed the ani-mals just as Leidy did with HADROSAURUS, in an upright, kangaroo-like pos-ture. To do so, Dollo had to inflict a severe bend in the tail. In life, truth betold, the tail would require breaking to accommodate such a posture. But onething Dollo did get correct was that IGUANODON did not have a nose horn like arhinoceros. The spike belonged with its thumb, not on its nose.

In the twentieth century, the British paleontologist David B. Norman of thethe Sedgwick Museum of Earth Sciences at the University of Cambridge inEngland, has shown clearly that IGUANODON’s backbone was essentially hori-zontal, its thick tail helping balance the weight of the front of the animal, thecenter of gravity cantilevered over its hips. The creature was only partiallybi-pedal and could balance comfortably on all fours, its tail stiff and straight,not dragging in the least.

IGUANODON, as a singleexample, helps showhow accumulation ofknowledge changes per-ceptions, how dinosaurssuch as IGUANODON

“evolved” in the minds ofhumans from giant rhi-noceros-like lizards tohuge reptilian kangaroosto our present vision ofthem as unique animalsin no way like rhinos orkangaroos. Owen had farless to work with than didDollo. And DavidNorman, in the centuryjust past, had the benefitof vastly more informa-tion. That is how science works.

Pliny Moody’s Tracks

Amherst College (Amherst, Massachusetts) geologistEdward Hitchcock (1793–1864) first saw the slab in1835 and recognized the footprints as those of anancient animal that had been fossilized in the rock.According to Hitchcock, the slab was discovered by ayoung man named Pliny Moody (ca. 1791–1868), about1802, as he was plowing his father Ebenezer’s field inSouth Hadley. Moody, with typical New England practi-cality, put it to use as the family doorstep. He called thefootprints those of “Noah’s raven,” apparently thinkingthat only a bird out of the Bible could have made tracksof such impressive size.

Just a few months later, Hitchcock published his firstscientific paper on the tracks in the prestigious AmericanJournal of Science. He called his new branch of scienceornithichnology, meaning “the study of stony bird tracks.”Later, he shortened the name to ichnology. Today, ichnology refers to the study of tracks left by ancient animals while alive, including footprints, tail-skin impres-sions, bite marks, nests, and even fossilized feces.Sources: Pick, Nancy. “King of Prints.” Amherst Magazine. Amherst

College. Amherst, MA: Fall, 2005. Emily Gold Boutilier, Office ofPublic Affairs, Amherst College, Amherst, MA; Joe Rodio, Director,Town of South Hadley Public Library, and the South Hadley TownClerk’s Office, South Hadley, MA, http://www.southhadleyma.org.

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1. Who first coined the name “dinosaur” and why were dinosaurs recognizedas a group apart from other vertebrate animals?

2. Why does the history of Iguanodon represent a good example of how sci-ence actually works?

McGowan, Christopher. The Dragon Seekers: The Discovery of DinosaursDuring the Prelude to Darwin. London: Little, Brown, 2001.

Colbert, Edwin H. Dinosaurs: An Illustrated History. Maplewood, NJ:Hammond Inc., 1983.

———. The Great Dinosaur Hunters and Their Discoveries. Reprint. NewYork: Dover, 1984.

Lessem, Don. Dinosaurs Rediscovered. New York: Touchstone, 1992.

1. The Linda Hall Library of Science, Engineering, and Technology websiteprovides a short overview of Robert Plot’s part in the history of dinosaurswith an article entitled “Plot’s Unrecognized Dinosaur Bone, 1676” —http://www.lindahall.org/events_exhib/exhibit/exhibits/dino/plo1676.htm

2. The University of California Museum of Paleontology features a biographyof Mary Anning — http://www.ucmp.berkeley.edu/history/anning.html

3. The Amherst Magazine website at Amherst College provides an excellentstory entitled “King of Prints” by Nancy Pick from its fall 2005 issue. PlinyMoody’s discovery of dinosaur tracks on his father’s farm is detailed in thearticle about Amherst College’s renowned geologist, Edward Hitchcock —http://www.amherst.edu/magazine/issues/05fall/king_prints

4. Dinohunters.com provides a timeline of Gideon Algernon Mantell’s workand several pages pertinent to IGUANODON and other dinosaurs —http://www.dinohunters.com/Mantell/Dates.htm

5. Richard Owen’s biography is featured at the University of CaliforniaMuseum of Paleontology website —http://www.ucmp.berkeley.edu/history/owen.html

6. The Academy of Natural Science in Philadelphia website provides the storyof Joseph Leidy and his work involving dinosaurs —http://www.ansp.org/museum/leidy/index.php

Other Books of Interest

Websites to Visit

�Questions

Suggested Reading

FOR GREATER UNDERSTANDING

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ne way to become immortal, at least in a manner of speak-ing, is to have a scientific specimen named after you. Twosmall and rather undistinguished dinosaurs, one namedOTHNIELLA, the other named DRINKER, celebrate the livesof two of the most ambitious of the dinosaur scientists,Othniel Charles Marsh and Edward Drinker Cope.

Both Marsh and Cope lived during the latter half of thenineteenth century and each contributed much to the grow-

ing knowledge of dinosaurs. But they became rivals, bitter rivals,and engaged in what has become known as “The Bone Wars.” The wars,such as they were, were fought in the vast fossil fields of western NorthAmerica at a time when the West was still a difficult and dangerous place. Thespoils were measured in dinosaur and other vertebrate fossils and both Marshand Cope competed to see who could unearth the most and name the mostfossil vertebrates.

O.C. Marsh was director of the natural history museum at Yale University(New Haven, CT), named the Peabody Museum in honor of Marsh’s uncle,George Peabody, a highly successful industrialist who, at his nephew’srequest, supplied funding to build the museum.

E.D. Cope was born of wealthy Quaker parents in Philadelphia and he was, for most of his life, associated with the Philadelphia Academy of Natural Sciences.

While their common interest in fossil vertebrates made them initially friends,the rivalry between Marsh and Cope began not long after they met. Both weremen of means and both would pay handsomely for fossils such that each soontried to get the better of the other. One reason for Cope’s apparent hatred forMarsh was that Marsh embarrassed Cope by pointing out that Cope hadplaced the skull on the wrong end of a giant fossil marine reptile called a PLE-SIOSAUR. Cope thought the long neck was the animal’s tail! Cope’s disgust forMarsh intensified when Marsh paid for dinosaur bones also offered to Cope,and Cope was forced to send the bones to Marsh, even as he was attemptingto describe them for publication.

From about 1866 through the early 1890s Marsh and Cope paid teams ofmen to excavate dinosaur bones from deposits scattered around the West.Cope spent considerably more time afield then Marsh. Conditions were diffi-cult. Travel was rigorous and risky, winters were highly challenging (thoughwork continued), and indigenous people posed some safety risk. Nonethe -less, many tons of dinosaur bones from both the Jurassic and Cretaceousperiods were dug or even blasted from rock, prepared and then loaded on to

The Suggested Reading for this lecture is David Rains Wallace’s TheBonehunters’ Revenge.

Lecture 4:The Bone Wars

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mule and ox-drawn wagons, transported to railheads, and moved east, someto New Haven, some to Philadelphia.

No direct hostilities ever occurred between either the two principals or theirhired workers, though Cope’s team and Marsh’s team did encounter oneanother on occasion and may not have liked being in each other’s company.They were secretive, and they sometimes destroyed bones rather than havethem taken by the other team. The real measure of the Bone Wars was inpublication. Both Cope and Marsh sought legacy through describing andnaming fossil vertebrates, not just dinosaurs but mammals (abundant afterthe dinosaur extinction) as well.

The rush to name things resulted in some species inadvertently being namedseveral times, depending upon where the bones were found and how com-plete the skeleton was. For example, Marsh initially named an animal hecalled APATOSAURUS and later, when he described a different and more com-plete skeleton, he named that animal BRONTOSAURUS. But both fossil bone setswere from different individuals of the same kind of animal and thus the nameAPATOSAURUS, which came first, is the recognized scientific name of one of themost iconic of the dinosaurs, the long-necked sauropod “thunder lizard” of the Jurassic.

Thanks to the untiring zeal of O.C. Marsh and E.D. Cope, we have come toknow dinosaurs such as ALLOSAURUS, APATOSAURUS, CERATOSAURUS,CAMARASAURUS, DIPLODOCUS, STEGOSAURUS, and TRICERATOPS. Though the bitterrivalry was unfortunate perhaps, the results were that museums began toexhibit amazing dinosaur skeletons and the public began to develop a keeninterest if not yet a full understanding of these remarkable extinct animals.

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1. How did Cope and Marsh become such bitter rivals?

2. How did this rivalry contribute to growing knowledge about dinosaurs?

Wallace, David Rains. The Bonehunters’ Revenge. Boston: HoughtonMifflin, 1999.

Lanham, Url. The Bone Hunters. New York: Columbia University Press, 1973.

Ostrom, John H., and John S. McIntosh. Marsh’s Dinosaurs. New Haven:Yale University Press, 1966.

“The Bone Wars: Othniel Charles Marsh, Edward Drinker Cope, and the YaleExpedition of 1870” from Wyoming Tales and Trails website —http://www.wyomingtalesandtrails.com/bonewars2.html

Websites to Visit

�Questions

Suggested Reading

FOR GREATER UNDERSTANDING

Other Books of Interest

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he American Museum of Natural History, located atCentral Park West in Manhattan, opened to the public in1877. Its first president, Morris K. Jesup, sought toinclude dinosaurs among the growing exhibits of the

museum. He hired a young aristocratic man just out ofPrinceton University, his Ph.D. in vertebrate paleontology.

This man, Henry Fairfield Osborn, would eventually succeedJesup as museum president, and would oversee the acquisi-tion of a huge collection of vertebrate fossils, including the

world’s most outstanding collection of dinosaurs.

Osborn assembled a talented team of field paleontologists as well as excel-lent fossil preparators. By the beginning of the twentieth century the museumwas assembling and exhibiting dozens of noteworthy skeletons and other fos-sil material. Osborn secured funding not only for expeditions, but also to pur-chase whole collections, such as that of E.D. Cope. He also used his person-al riches to fund the growth of the collection.

Osborn was a scholar who wrote about evolutionary biology and whobelieved strongly in a concept called orthogenesis. This posits that evolution-ary directions are in some way predetermined and thus animal lineages showclear directional trends. Many of Osborn’s fossil exhibits were designed byhim to reflect this now largely discredited concept. Osborn also held strongbeliefs regarding human evolution, convinced that Homo sapiens emergedfirst in Asia. A major reason why Osborn strongly supported the museum’sambitious Central Asiatic Expeditions of the 1920s was an attempt to provehis theory about human origins. Osborn also recognized that dinosaurs werea wonderful drawing card for the general public and thus he enthusiasticallysupported collecting as many dinosaurs as he could get.

Barnum Brown was hired by Osborn to be his chief fossil hunter and he suc-ceeded beyond all expectations. Brown had a sixty-six-year career at themuseum and traveled to many remote locations to find and extract dinosaurskeletons. Much of the museum’s remarkable collection is attributable toBrown’s efforts.

One of Brown’s most famous discoveries was from a place in Montana calledHell Creek. There he found several partial skeletons and an almost completeskeleton of a huge animal that Osborn initially named Dynamosaurus imperio-sus. Osborn’s more detailed analysis led him to change the animal’s name toTYRANNOSAURUS REX. The animal was mounted as bipedal with its back archingup, its head high above the ground, its tail dragging behind it, an image of T. REX that would persist for most of the twentieth century.

The Suggested Reading for this lecture is Mark A. Norell, Eugene S.Gaffney, and Lowell Dingus’s Discovering Dinosaurs in the AmericanMuseum of Natural History.

Lecture 5:The Museum That Dinosaurs Built

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Barnum Brown also unearthed numerous dinosaurs from the Red Deer Riverin southern Alberta, Canada. He invented the technique of floating down theriver aboard a large raft of his own design fully equipped for fossil hunting,with a tent and cooking stove, searching for dinosaur outcrops along thesteep cliffs that lined the river.

Brown was not the only skilled fossil hunter employed by Osborn. WalterGranger was also a distinguished dinosaur finder. Some of his most notablework was ultimately due to the efforts of a man who was more of a boldexplorer than a careful and deliberate paleontologist. This man was RoyChapman Andrews, the alleged inspiration for the film character “IndianaJones.”

Andrews worked his way up at the museum and was the principal organizerof a series of five expeditions to Outer Mongolia. The first of these began inthe summer of 1922. Andrews literally drove across vast uncharted miles ofdesert in automobiles supplied by the Dodge Motor Company. He arrangedfor long camel caravans to meet his team at various locations to bring sup-plies, including gasoline for the vehicles.

Andrews’s expeditions were successful in finding numerous fossil mammalsand lots of dinosaurs. At a place they nicknamed “The Flaming Cliffs,” theyfound eggs of dinosaurs, the first real confirmation that dinosaurs laid eggs.They also excavated numerous skeletons of a new kind of dinosaur calledPROTOCERATOPS. The expeditions excited the public about the museum andabout dinosaurs and helped immensely to build the museum’s collection andreputation. Andrews eventually became the president of the AmericanMuseum of Natural History. He is also known for his books, written both foradults and children, giving lively accounts of his adventures.

Another essential person in the American Museum’s dinosaur program wasthe artist Charles R. Knight. He emerged as the preeminent illustrator of theprehistoric world. His murals and other paintings are exhibited at the ChicagoField Museum and Los Angeles County Museum of Natural History as well asthe American Museum of Natural History. His career began and much of hiswork was done at and for the American Museum in New York, where heworked closely with Henry Fairfield Osborn. Knight’s evocative illustrationswere widely reproduced for most of the century in any and all dinosaur booksor articles about dinosaurs. In some ways, Knight basically defined the variousdinosaurs and he also seems to have anticipated the change in perception ofdinosaurs that occurred in the latter part of the twentieth century, as dinosaurscame to be seen as more dynamic and bird-like in their behavior.

Edwin H. Colbert continued the American Museum’s activity in dinosaurexcavation in the mid-twentieth century working mostly in New Mexico at aplace called Ghost Ranch. He unearthed numerous vertebrate skeletons fromthe Triassic period, including many small predatory dinosaurs of the genusCOELOPHYSIS. One year before his retirement from the museum at the age ofsixty-five, he helped unearth a mammal-like reptile called LYSTROSAURUS fromAntarctica, providing strong support that Antarctica had once been fused withAfrica, where LYSTROSAURUS was also uncovered.

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The museum continues as a leading repository of dinosaur skeletons andother fossil material. From 1991 to 1996 it completely reorganized its exhibitson vertebrate evolution and remounted both its T. REX and APATOSAURUS

skeletons to positions thought now to be most accurate. The museum contin-ues to explore Asia and other places, adding to its collections and to ourknowledge of the prehistoric world.

1. Why did Henry Fairfield Osborn give so much attention and effort towardbuilding the dinosaur collection at the American Museum of Natural History?

2. What obstacles did Roy Chapman Andrews have to overcome in planningand executing the five Central Asiatic Expeditions in the 1920s?

Norell, Mark A., Eugene S. Gaffney, and Lowell Dingus. DiscoveringDinosaurs in the American Museum of Natural History. New York: AlfredA. Knopf, 1995.

Bird, Roland T. Bones for Barnum Brown. Fort Worth, TX: Texas ChristianUniversity Press, 1985.

Czerkas, Sylvia Massey, and Donald F. Glut. Dinosaurs, Mammoths, andCavemen: The Art of Charles R. Knight. New York: E.P. Dutton, Inc., 1982.

Gallenkamp, Charles. Dragon Hunter: Roy Chapman Andrews and theCentral Asiatic Expeditions. New York: Viking, 2001.

Rainger, Ronald. An Agenda for Antiquity: Henry Fairfield Osborn andVertebrate Paleontology at the American Museum of Natural History,1890–1935. Tuscalosa, AL: University of Alabama Press, 1991.

Sternberg, Charles Hazelius. Hunting Dinosaurs in the Bad Lands of the RedDeer River, Alberta, Canada. Edmonton: NeWest Press, 1985.

Wallace, Joseph. The American Museum of Natural History’s Book ofDinosaurs and Other Ancient Creatures. New York: Simon &Schuster, 1994.

1. The American Museum of Natural History — http://www.amnh.org

2. Carnegie Museum of Natural History — http://www.clpgh.org/cmnh

3. The Field Museum of Natural History website features “The World ofCharles R. Knight” — http://www.charlesrknight.com/fmnh.htm

4. Smithsonian Institution National Museum: Natural History —http://nmnh.si.edu/departments/paleo.html

Websites to Visit

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inosaurs have become very much a part of pop culture.For many years the comic strip Ally Oop featureddinosaurs and humans sharing the same prehistoricworld. Later came The Flintstones and later still camethe child-friendly purple dinosaur Barney. Anyone famil-iar with the unique humor of Gary Larson’s cartoons

knows how much dinosaurs are part of our psyche. Howdid they get there?

The first real burst of “Dinomania” was likely the GreatExhibition in Great Britain at the height of the Victorian Era, when RichardOwen supervised Waterhouse Hawkins in modeling full-sized replicas of whatdinosaurs and other prehistoric creatures were thought to have looked like.That drew a crowd. But it wasn’t until the twentieth century that dinosaursreally took hold of the public imagination in the United States. That happenedwith a cartoon.

One of the first animated cartoons ever produced was Gertie the Dinosaur,released in 1914. Gertie was a rambunctious BRONTOSAUR that was, nonethe-less, charming and clever. In one sequence Gertie tosses a woolly mammothinto a pond, only to have the mammoth retaliate by squirting Gertie.

Soon after, in 1919, came a short film, The Ghost of Slumber Mountain. Thefilm was a fantasy, where looking through a certain magical telescope wouldreveal the prehistoric world. Featured were moving dinosaurs modeled afterthe images of dinosaurs by Charles R. Knight, created and animated bysomeone who would become a legend in the film industry, Willis O’Brien.Public reaction was enthusiastic. Now, thanks to films, people could begin toimagine dinosaurs as real animals.

Sir Arthur Conan Doyle, famous for his detective Sherlock Holmes, also con-tributed mightily to connecting dinosaurs with the general public. In 1912 hisscience fiction novel The Lost World was published. It featured a land ofdinosaurs and cave people atop a table mountain in remote northeasternSouth America. The book was good but the American public would like themovie even better.

The Lost World was produced as a feature film in 1925 for the then stagger-ing cost of a million dollars. It starred Wallace Beery as Professor GeorgeChallenger, but the real stars, just as with Jurassic Park sixty-eight yearslater, were the dinosaurs. This silent black-and-white film was a huge boxoffice success. Even by today’s standards, the animation remains amazing.There are vivid scenes filled with animated dinosaurs so lifelike that somemoviegoers actually wondered if they really were actual dinosaurs.

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The Suggested Reading for this lecture is Jose Luis Sanz’s Starring T.Rex!: Dinosaur Mythology and Popular Culture.

Lecture 6:Dinosaurs Enter Pop Culture

Willis O’Brien, nicknamed “Obie,” continued to perfect his technique of stop-motion photography. This requires that a metal armature of an animal be builtsuch that it can be moved in positions that the actual animal might assume.Then the armature is molded lifelike with clay and finished with rubbery skinand realistic features. It is then moved ever so slightly as the film is shotframe by tedious frame. But, when done like Obie did it, it is amazingly effec-tive and realistic.

The Lost World established the formula for many a film to come. A prehistoriccreature is found and brought back to a big city. It escapes, reeks havoc, andis finally killed or goes away. In The Lost World, after collapsing the LondonBridge, the previously captive BRONTOSAURUS swims down the Thames and outof the film. The general public found movie dinosaurs to indeed be “fearfullygreat lizards,” but not insurmountable adversaries. They were kind of fun.

Willis O’Brien followed his success in The Lost World by animating KingKong, released in 1933. This film was a blockbuster and featured severaldinosaurs in addition to the giant ape. The most outstanding sequence involv-ing a dinosaur was the titanic battle between a T. REX and Kong. That sceneremains a classic in American film.

Thanks to the growth of museums and the use of dinosaurs in successfulfilms, the American pubic had come to know dinosaurs and be interested in them.

The Sinclair Oil Company promoted dinosaurs when it adopted aBRONTOSAURUS as its mascot and funded the construction of life-sizeddinosaurs for the Chicago World’s Fair in 1933–1934. The company contin-ued to feature dinosaurs in stamps, plastic models, and other collectablesand again sponsored the construction of full-sized dinosaur models for theNew York World’s Fair in 1964–1965.

Many films of the 1950s featured dinosaurs, but two of the most notable areThe Beast from 20,000 Fathoms (1953) and The Animal World (1956). Bothwere animated using stop-motion by a student of Willis O’Brien’s named RayHarryhausen. Harry hausen went on to a highly distinguished career as a stopmotion film animator. The Beast, adopted from a Ray Bradbury short story,was a classic 1950s apocalyptic film of the still-young atomic age where, yetagain, a prehistoric animal runs rampant in a big city and this time must becleverly killed by the very military folk who released it in the first place. TheAnimal World featured only ten minutes of dinosaur scenes, but they weremeant to illustrate the animals in their Mesozoic habitats interacting amongthemselves. The dinosaurs were lumbering, tail dragging, and reptilian, butthey did reflect how science envisioned them at the time.

The 1950s was a time when baby-boomer children embraced dinosaurs. Toydinosaurs were sold by various companies, the aforementioned films werebox office hits, and even comic book series such as Turok Son of Stone fea-tured many kinds of dinosaurs.

One boost to dinosaur popularity in the 1950s was an incredible cover storyby Life Magazine titled “Two Billion Years of Evolution.” On the cover of itsSeptember 7, 1953, issue was a BRONTOSAURUS and STEGOSAURUS, part of thePeabody Museum mural by Rudolf Zallinger. The fold-out mural of dinosaurs

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depicting “The Age of Reptiles” that accompanied the story did much to stim-ulate interest in dinosaurs.

But the political and social turmoil of the 1960s was such that dinosaurswere rather eclipsed. The space race may have replaced the prehistoricworld in the public mind. That began to change quickly in 1975 when a youngpaleontologist named Robert Bakker published an article in ScientificAmerican magazine with the title “Dinosaur Renaissance.” The idea thatdinosaurs may have been active and perhaps warm-blooded like birds andmammals caught on with the public. Interest in dinosaurs grew again as pop-ular articles in newspapers and magazines reported the new thinking aboutdinosaurs and the debates it inspired.

The combination of swift, smart, dangerous dinosaurs and genetic engineer-ing came together in 1990 with the bestselling Jurassic Park by MichaelCrichton. This was, of course, made into one of the most successful films inhistory in 1993, directed by Steven Spielberg. This film is most important forits animation breakthrough, the use of computer imagery to animatedinosaurs. No film up to then ever depicted dinosaurs as so lifelike.

Use of computer technology has flourished since. The highly acclaimedBritish series Walking with Dinosaurs, released in 1999, has spawned manyother similar efforts.

Dinosaurs have had a renaissance, not just in how science perceives thembut in how the general public embraces them. Museums have flourished andincreased their dinosaur exhibits, theme parks feature dinosaurs, travelingexhibits of semi-animated dinosaurs remain popular, and many lines of toys,replicas, and models are available to the dinosaur enthusiast. There is even adinosaur magazine featuring both the science and hobbyist aspects ofdinosaurs, Prehistoric Times.

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1. When and how did dinosaurs first enter pop culture in Great Britain andlater in the United States?

2. How have dinosaurs in motion pictures contributed to the public perceptionof dinosaurs and how does that compare with how scientists viewed them?

Sanz, Jose Luis. Starring T. Rex!: Dinosaur Mythology and Popular Culture.Bloomington, IN: Indiana University Press, 2002.

Berry, Mark F. The Dinosaur Filmography. Jefferson, NC: McFarland andCompany, 2002.

Cain, Dana, and Mike Fredericks. Dinosaur Collectables. Norfolk, VA: AntiqueTrader Books, 1999.

Debus, Allen A., and Diane E. Debus. Paleoimagery: The Evolution ofDinosaurs in Art. Jefferson, NC: McFarland and Company, 2002.

Glut, Donald F. The Dinosaur Scrapbook. Secaucus, NJ: Citadel Press, 1980.

Webber, Roy P. The Dinosaur Films of Ray Harryhausen. Jefferson, NC:McFarland and Company, 2004.

Prehistoric Times. Published quarterly. 145 Bayline Circle, Folsom, CA 95630(www.prehistorictimes.com).

The Dinosauricon is a website devoted to dinosaur information and illustration— http://dino.lm.com/pages

Magazine of Interest

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inosaurs flourished (excluding birds, which still flourish)for approximately 165 million years. They lived during atime geologists call the Mesozoic Era, the “Age ofMiddle Life.” It is essential in tracing the evolutionaryorigin of dinosaurs to understand something about theage of the Earth and geologic time scales.

The Solar System—the Sun, Earth, planets, and otherbodies such as comets and asteroids—is considered to be

4.6 billion years old. This age is based on careful radiometricdating from a variety of sources, including moon rocks. The universe itself isestimated to have begun 13.8 billion years ago, so Earth and the rest of theSolar System are only about one-third the age of the universe.

Earth formed as a “byproduct,” as did other planets when the Sun formed bygravitational contraction within a large nebula. Our planet was initially moltenand lifeless. But trace fossils suggest that life evolved by 3.8 billion yearsago. From that point until about 2.5 billion years ago, all life was microbial,various forms of bacteria called prokaryotes. Complex cells, called eukary-otes, evolved about 2.5 billion years ago and eukaryotic multicellular life islikely less than a billion years old. It was not until the start of the PaleozoicEra, 543 million years ago, that multicellular life, plants and animals, becameabundantly represented in the fossil record. This surge in life-forms and com-plexity may have had much to do with increasing oxygen levels (produced byplants during photosynthesis).

If the history of Earth is compressed into but a single year, with the forma-tion of the planet on January 1, the first complex animal communities wouldnot appear until about November 20. Dinosaurs would dominate the planetfrom December 21–27. Primitive humans would not appear until 9:07 PM onDecember 31 and Homo sapiens, modern humans, would not appear until fif-teen minutes before midnight.

How did the dinosaurs evolve? Who were their ancestors?

Dinosaurs, like humans, are vertebrate animals, animals with backbones. Allvertebrates are part of a phylum called Chordata, meaning animals with aflexible notochord running the length of their back. In vertebrates, bony verte-brae largely replace the notochord during fetal development. Our interverte-bral disks are the remains of our original notochord. Vertebrates share otherchordate characters (such as a hollow nerve cord atop the vertebral column)as well as possessing unique characters placing them in the subphylumVertebrata, such as forming a skeleton of bone.

The Suggested Reading for this lecture is Stephen Jay Gould’s TheBook of Life.

Lecture 7:Dinosaur Origins

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Vertebrates were present in the earliest part of the Paleozoic Era, theCambrian period, thus their history goes back at least 500 million years.Earliest vertebrates were small marine animals, like tiny tadpoles. Vertebratesgrew larger and diversified throughout the Paleozoic Era, which lasted from543 to 248 million years ago. The Devonian period, 410 to 360 million yearsago, is often termed the “Age of Fishes” because of the great diversity of fishtypes then present. The most significant event of the Paleozoic Era waswhen one group of fishes became tetrapods (four-footed) by developing mus-cular limbs with digits. Some of these earliest tetrapods adapted to breatheoxygen from the atmosphere and become mobile on land. This groupbecame the amphibians, an event that occurred in the late Devonian Period,about 380 million years ago.

Reptiles differ from amphibians in many respects, but in the early stages ofreptile evolution the differences are not obvious. The most critical differenceis that reptiles lay amniotic or cleidoic eggs (like a chicken egg) that have ahard protective shell and contain nourishing membranes within the egg tofeed and protect the developing embryo. Reptiles, mammals, and birds aremodern Amniotes. Early reptiles also have more vaulted, less flattened skullsthan amphibians. Reptiles evolved in the Carboniferous period, about 320million years ago.

Early reptiles, called Anapsids, had a solidly roofed skull. But by the lateCarboniferous and into the Permian period that followed, reptiles diversifiedand flourished. One group, named the Synapsids, developed a skull with anopening low on the skull behind the eye. This opening permitted more effec-tive muscle attachment to operate the jaws. After millions of years, in theTriassic period at around the same time as dinosaurs first appeared, truemammals evolved from advanced synapsids.

Another primitive reptilian group developed a single opening high on itsskull, behind the eye. This group, the Euryapsids, gave rise to two diversegroups of marine reptiles, the plesiosaurs and ichthyosaurs.

Still another reptile lineage had not one but two openings behind the eye onthe skull. This group, called the Diapsids, diversified into many lineages.One lineage, called the Lepidosaurs, became the group giving rise to lizardsand snakes.

But the most diverse group of diapsid reptiles was one called theArchosaurs. Archosaurs shared certain skull characters in common, includingan opening in front of the eye as well as two behind the eye, plus an openingin the lower jaw. They were also adapted for relatively upright posture, withlonger hind limbs so they were able to move effectively, some even able togallop, some bipedal. Archosaurs gave rise to crocodilians (alligators andcrocodiles), flying reptiles called pterosaurs, and—to dinosaurs.

Dinosaurs as a group are most closely related to pterosaurs, and bothdinosaurs and pterosaurs are in a general group called Ornithodires. Thisname refers to the unique ankle joint, which is hinge-like, allowing only for-ward and backward motion that supports active locomotion.

There were three major extinction events in the Paleozoic Era. Major extinc-tions occurred in the Ordovician and Devonian periods. The largest major

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extinction of all time ended the Paleozoic Era some 248 million years ago. Itis estimated that up to 90 percent of species perished in the course of thismajor extinction. But those that survived provided the basis for a significantdiversification that characterized the Triassic period, the first of three periodsof the Mesozoic Era. The Triassic ranged from 248 to 206 million years ago.Approximately 228 million years ago, dinosaurs appear in the fossil record.

Dinosaurs all share a set of defining characteristics. These are (1) uprightposture with a thigh bone whose head is angled to fit into an opening(acetabulum) in the pelvis (hip); (2) a perforated (that is, a “hole”) acetabulumin the pelvis; (3) at least three sacral vertebrae fused with the ilium bone ofthe hip. Originally dinosaurs were bipedal and many dinosaurs remained so,but some dinosaur lineages became secondarily quadripedal, moving on allfour appendages. Even these forms typically retained shorter anteriorappendages (“arms”) than posterior appendages (“legs”).

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1. When did dinosaurs first evolve and from what group of animals?

2. What anatomical characteristics actually identify an animal as beinga dinosaur?

Gould, Stephen Jay, ed. The Book of Life. New York: W.W. Norton, 2001.

Fortey, Richard. Life: A Natural History of the First Four Billion Years of Lifeon Earth. New York: Vintage Books, 1997.

Norman, David. Prehistoric Life and the Rise of the Vertebrates. New York:Macmillan, 1994.

Reader, John. The Rise of Life: The First 3.5 Billion Years. New York: AlfredA. Knopf, 1986.

The Journal of Dinosaur Paleontology —http://www.dinosauria.com/jdp/jdp.htm

Journal of Interest

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inosaurs were the dominant terrestrial animals for most ofthe Mesozoic Era, which began 248 million years agoand ended 65 million years ago. Based on biostratigra-phy, the study of the fossils in sedimentary rocks, pale-ontologists divide the Mesozoic into three periods.These are the Triassic (248 to 206 million years ago),

the Jurassic (206 to 144 million years ago), and theCretaceous (144 to 65 million years ago). The oldest

dinosaur bones are dated at 228 million years ago (upperTriassic), so dinosaurs were present from then until only the avian dinosaurs(birds) remained, 65 million years ago, a time span of 163 million years. Butdinosaurs did not diversify and become dominant until early in the Jurassicperiod. Thus it is the Jurassic and Cretaceous periods that together comprisethe real “Age of Dinosaurs.”

At the dawn of the Mesozoic Era, Earth’s various ecosystems had collectivelysuffered the most catastrophic mass extinction that has ever occurred. Over90 percent of all animal species failed to survive from the Permian into theTriassic. The cause of the great extinction remains largely a mystery, butextraordinary volcanic action is believed to be involved, causing atmosphericchanges that could have triggered the extinction. As recovery slowly began,opportunities for evolutionary and ecological divergence were great and soonmany groups of animals were diversifying.

Looking at a map of the world in the Triassic period would pose challenges inlocating, say, Florida, Italy, India, Scotland. All of today’s continents werefused into a giant single continent named Pangea. The world’s oceans werethen but one ocean, the Sea of Panthalassa. But midway into the Triassic,Pangea began to break apart and slowly, at rates of between one and twocentimeters annually, continental drift began as tectonic plates separated. Bythe end of the Cretaceous period, a world map would bear a strong resem-blance to today’s continental distribution.

The Triassic period was a time of seasonal changes within an overall hotand arid environment. Desert conditions prevailed in many areas. Tempera -tures were warm but variable and shortage of water may have limited distrib-ution of animals. The most prevalent plants were forests of tall coniferoustrees similar to today’s pines and cypresses. There were no flowering plantsas they would not evolve until the Cretaceous period. In addition to conifers,many cycads, with stiff palm-like leaves, were present as well as large seedferns and giant horsetails. Invertebrates such as insects, spiders, scorpions,and earthworms were abundant and were a food base for some vertebrates.

The Suggested Reading for this lecture is Edwin H. Colbert’s The Ageof Reptiles.

Lecture 8:In the Days of Dinosaurs

Most large amphibians failed to survive the Permian extinction, but somedid. Among them a group called the metoposaurs, which could reach lengthsof six feet. Other smaller amphibians eventually evolved into today’s frogs,toads, and salamanders.

Among the unique reptile groups evolving in the Triassic were ichthyosaursand plesiosaurs. Ichthyosaurs first appeared in the early Triassic. Ichthyosaurswere fish-like in shape but were air-breathing euryapsid reptiles, evolved fromland-dwelling ancestors, but adapted to a totally aquatic ecology. One Triassicichthyosaur, SHONISAURUS, was huge, weighing up to forty tons, perhaps thelargest animal of the Triassic. By the late Triassic, sea serpent-like plesiosaursevolved, also from terrestrial ancestors. Like ichthyosaurs, they were euryap-sid reptiles, but their bodies resembled sea turtles, compact with huge flipperfins. Some had long necks and small skulls, and some had short necks andelongated skulls. All appear to have been predators likely feeding on fish andsquid. Both icthyosaurs and plesiosaurs would continue to diversify and bothgroups persisted until the Cretaceous extinction event.

Pterosaurs first appear around the time of dinosaur emergence, about 228million years ago in the late Triassic. They were flying reptiles with wingssupported by a forearm and hand with an elongate fourth finger. Wings weremade of skin membrane reinforced by protein fibers. Many if not all had ahair-like covering and were likely warm-blooded. Many forms of pterosaursevolved and some that lived late in the Mesozoic had wing spans of up toforty feet or more. All pterosaurs perished at the end of the Cretaceous.

Perhaps the most abundant vertebrate animal of the early Triassic wasLYSTROSAURUS, a dicynodont (“double dog-tooth”) mammal-like synapsid.These sheep-sized, stocky, four-legged grazers abounded in many places.Other synapsids were significant predators, such as a wolf-like group calledthe gorgonopsids. Gradually a group of synapsids called cynodonts (“dog-tooth”) evolved to be increasingly mammalian until true mammals emergedabout 228 million years ago, approximately when dinosaurs first appeared.

Diapsid reptiles, especially the Archosaurs, were highly diverse in theTriassic. One group, the rauisuchians, were the largest of the land predators,resembling a cross between a predaceous dinosaur and crocodile.POSTOSUCHUS was a rauisuchian that reached a length of twenty feet. Truecrocodilians (Eusuchia) also evolved in the Triassic as did phytosaurs, a dif-ferent group of archosaurs that closely resembled true crocodilians. Onegroup of small agile reptiles, typified by an animal called EUPARKERIA, waspartly bipedal, sometimes running on hind legs and using the tail as a coun-terweight and balancing organ. These animals, collectively called thecodonts(“tooth in socket”), resembled dinosaurs and one group of them likely evolvedinto the first dinosaurs.

The earliest true dinosaurs were EORAPTOR and HERRERASAURUS, bothunearthed in Argentina and estimated at 228 million years old. These weresmall predatory dinosaurs. Later, in New Mexico, there were large numbers ofa small (forty pound) predatory dinosaur called COELOPHYSIS. By the lateTriassic, at least two fairly large dinosaurs, PLATEOSAURUS (one-and-a-halftons) and RIOJASAURUS (three tons), had evolved. Both were plant eaters dis-tantly related to the large long-necked Brontosaur types that would come later.

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The Jurassic saw a great diversification of dinosaurs. They became the pre-dominant land vertebrates. Mammals remained small and inconspicuous.The Jurassic world was less arid and more tropical than the Triassic. Sealevels slowly rose. The central part of North America was inundated with thegreat Sundance Sea. Rainfall increased, making the climate even more trop-ical. Overall, the climate was warm, with no polar ice caps. Dominant treeswere gymnosperms, conifers such as cedars, pines, cypresses, and arau-carias (monkey-puzzle trees). Ginkgos, many fern species, and cycads wereabundant. The Jurassic landscape would look familiar but for the lack offlowering plants.

Huge herbivorous dinosaurs, the giant sauropods such as DIPLODOCUS andAPATOSAURUS, herded across the Jurassic landscape. Other plant eaters suchas well-armored stegosaurs and ankylosaurs evolved, as did various forms ofearly ornithopod dinosaurs such as CAMPTOSAURUS. The dramatic increase inlarge herbivorous dinosaurs was likely related to the abundance of vegetationpresent during a time of equitable weather and tropical conditions. Smallpredatory dinosaurs such as COMPSOGNATHUS were present and largetheropods such as ALLOSAURUS likely stalked the herds of sauropods.Feathered dinosaurs evolved. ARCHAEOPTERYX, from the late Jurassic 150 mil-lion years ago, is often called the urvogel, the first bird.

The Cretaceous period was also equitable and warm, with no polar ice caps.Mild conditions prevailed even as far north as the latitude of northern Alaska.The central part of North America was extensively inundated with ocean, theNiobrara Sea. The major botanical event of the time was the evolution offlowering plants, the angiosperms, including the earliest of the grasses. Bythe late Cretaceous, flowering plants were becoming dominant componentsof most terrestrial ecosystems.

Immense predators inhabited Cretaceous seas. In addition to ichthyosaursand plesiosaurs of many kinds there were mosasaurs, giant sea-going moni-tor lizards. There were giant sharks in the sea and giant crocodiles alongshore, such as DEINOSUCHUS (thirty-five feet) and SARCOSUCHUS (forty feet),both of which likely preyed on dinosaurs.

Dinosaurs diversified, especially the ornithopods that evolved into manyforms of plant-eating duck-billed dinosaurs. There were also ceratopsians,the horned dinosaurs such as TRICERATOPS. An odd group called the bone-headed dinosaurs or pachycephalosaurs evolved. Anklylosaurs diversifiedtoo and long-necked sauropods, while less abundant than in the Jurassic,continued. Many large predators evolved, including giants such as T. REX,GIGANOTOSAURUS, and CARCHARODONTOSAURUS. Small predators includedVELOCIRAPTOR and DEINONYCHUS. Birds diversified as well as other forms offeathered dinosaurs. As continents separated they each had its array of dinosaurs.

The Cretaceous ended with a mass extinction that included all of the non-avian dinosaurs as well as the ichthyosaurs, plesiosaurs, mosasaurs, andpterosaurs. The only dinosaurs to escape the extinction were birds.

1. Name and describe the three periods of the Mesozoic Era.

2. What major groups of vertebrate animals, in addition to dinosaurs, werepresent in the Mesozoic Era?

Colbert, Edwin H. The Age of Reptiles. Reprint. Mineola, NY: Dover, 1997.

Benton, Michael J. Vertebrate Paleontology. 3rd ed. Malden, U.K.:Blackwell, 2005.

Burnie, David. The Kingfisher Illustrated Dinosaur Encyclopedia. New York:Kingfisher, 2001.

Cloudsley-Thompson, J.L. Ecology and Behavior of Mesozoic Reptiles.Heidelberg: Springer, 2005.

Czerkas, Sylvia J., and Stephen A. Czerkas. Dinosaurs: A Global View. NewYork: Mallard Press, 1991.

The University of California Museum of Paleontology, The PaleontologicalSociety of Franklin and Marshall College (Lancaster, PA), The Society ofVertebrate Paleontology at the University of Texas (Austin), and the UnitedStates Geological Society sponsor The Paleontology Portal —www.paleoportal.org

Websites to Visit

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o one knows how many kinds of dinosaurs there were.One recent study says that 527 genera have beendescribed thus far but estimates that up to 1,850 mayhave actually existed. If this is accurate, only about 29percent of all dinosaur genera have as yet been discov-ered. Even with 527 dinosaur genera, that seems a lot totry to describe. But dinosaur classification is fairly sim-ple. To begin with, there were only two main groups, or“clades,” of dinosaurs.

In 1887, a dinosaur expert named Harry Govier Seeley recognized that alldinosaurs had one of two basic hip arrangements. Seeley named one groupSaurischia, which means “reptile-hipped,” and the other Ornithischia, mean-ing “bird-hipped.” Dinosaur hips comprised three big bones: the ilium bone,which articulates with the vertebral column, the pubis bone, which is belowthe ilium and tends to face forward, and the ischium bone, which is belowthe ilium and faces backward. The open acetabulum, where the head of thefemur (thigh bone) articulates, is at the juncture of the three hip bones. Inthe case of Saurischians, the pubis is normally strongly forward and the iliumis deep and crescent-shaped. But in the Ornithischians, the pubis aligns par-allel to the ischium and faces to the rear. A spur called the prepubis facesforward. The ilium is elongated and anvil shaped. The Ornithiscians also hada character absent in the Saurischia, a bone called the predentary at thevery front of their lower jaw.

Dinosaurs, like most other animals, are classified using a system calledphylogenetic systematics, or, more simply, cladistics. This system involvesthe careful measurement of dozens, if not hundreds, of characters on eachspecimen. Then, using an algorithm, a computer compares each animal forall characters and produces a tree-like diagram depicting the most parsimo-nious comparative arrangement, a so-called cladogram showing degrees ofsimilarity. The assumption is that the more similar they are for specific char-acters, the more closely related they are in the evolutionary sense. Fordinosaurs, skeletal characters are obviously most used to generate clado-grams. Cladistics has proven very useful in understanding dinosaur phyloge-ny, the evolutionary relationship among dinosaur groups.

There are only two groups of dinosaurs within the Saurischia and they are wellknown, indeed, the very icons of Dinosauria. They are the plant-eating Sauro -podo morphs, which include the huge long-necks such as DIPLODOCUS andAPATOSAURUS, and the Theropoda, the meat-eaters that range from tiny COMP -SOGNATHUS to the fierce VELOCIRAPTOR to the immense TYRANNOSAURUS REX.

The Suggested Reading for this lecture is Paul Barrett’s NationalGeographic Dinosaurs.

Lecture 9:Dinosaur Diversity

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The Sauropodomorphs include the Prosauropods from the late Triassic andthe true Sauropods from the Jurassic to the end of the Cretaceous. Theselong-necked, long-tailed, elephantine behemoths were the largest animalsever to dwell on land. Their heads were generally tiny in comparison withtheir bodies and their teeth were usually simple peg or pencil-like. They musthave scraped and swallowed massive amounts of plant material and groundit within their stomach. Fossil skeletons are sometimes found with smoothstones called “gastroliths” that the animals may have swallowed to aid ingrinding plant material. The largest complete skeletons are those ofDIPLODOCUS (twenty tons), APATOSAURUS (thirty-five tons), CAMARASAURUS

(twenty tons), and BRACHIOSAURUS (up to fifty tons). But some were apparent-ly larger and heavier. SEISMOSAURUS is estimated to have reached one hun-dred fifteen feet in length, MAMENCHISAURUS had a neck that alone measuredthirty-two feet, and SUPERSAURUS and ULTRASAURUS, may have each exceed-ed fifty tons in weight.

The Theropoda comprise all of the carnivorous dinosaurs. They were per-haps the earliest dinosaurs to evolve and were present until the end of theCretaceous. Their classification is complex as there were many kinds ofvarying sizes and characteristics. They are best known by species such asALLOSAURUS of the Jurassic and TYRANNOSAURUS of the Cretaceous, but inrecent years, smaller species such as DEINONYCHUS and VELOCIRAPTOR havegotten much attention. Birds appear to be descended from a group oftheropods called Dromaeosaurs, thus birds are really a modern form ofSaurischian dinosaur. Various groups of theropods (besides true birds) mayhave had feathers and one bizarre group, the Therizinosaurs, may havebeen adapted primarily to a diet of vegetation.

As far as anyone knows, all Ornithischians were herbivores, existing entire-ly on a diet of plant food. There were four major groups, the Fabrosaurs, theOrnithopoda, the Thyreophora, and the Marginocephalia.

The Fabrosaurs were a group of early bipedal Ornithischians typified by asmall (six feet in length) dinosaur named LESOTHOSAURUS. There is somequestion as to how fabrosaurs should be classified. Some think they areearly ornithopods, but they differ from true ornithopods because they lack anumber of skeletal characteristics, including cheeks. Nonetheless, they mayhave been ancestors of true ornithopods. All were relatively small, adaptedfor speed, and only present from the late Triassic until the early Jurassic.

The Ornithopoda were a diverse and abundant group, especially in the midto late Cretaceous. Though capable of bipedal movement, they likely walkedmost commonly on all fours. Many had tails reinforced with bony tendonsthat kept the tail stiff, balancing against the weight of the front of the animal.Jurassic ornithopods included the generalized CAMPTOSAURUS found amongthe dinosaurs of the Morrison Formation. Weighing only about six hundredpounds, it resembled a small IGUANODON. The iguanodonts, includingTENONTOSAURUS, IGUANODON, MAIASAURA, and ANATOTITAN, ranged in weightfrom as little as six hundred sixty pounds to up to seven-and-a-half tons.Their most distinctive characteristics were their teeth and jaws, which werewell adapted to grinding massive amounts of plant food. The upper jawcould widen as the lower jaw closed, aiding in grinding vegetation. Hundreds

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of teeth within fleshy cheeks chewed plants into a pulp before swallowing.The hadrosaurs, often called duck-billed dinosaurs, included some speciesthat developed elaborate crests of bone on their heads. Aside from size,their bodies were scarcely different but their heads were each distinct. Likethe iguanodonts they had cheeks and jaws well adapted to chewing andgrinding vegetation. Teeth were easily replaceable, arranged in batteries inthe jaw and numbering in the thousands. The crests on some hadrosaursmay have served for species recognition both by appearance and by theunique sound they likely provided when the animal vocalized.

The Thyreophorans include two groups, the Stegosaurs, primarily Jurassic,and the Ankylosaurs, mostly Cretaceous. All were quadripedal and their forelegs were shorter than their hind legs. Thyreophorans are grouped togetherfor their unique forms of bony armor. They typically have bony plates,spikes, or imbedded bone within the skin, all presumably for protection anddefense. Stegosaurs are best known for the prominent bony plates thatadorned their backs. No one knows exactly what the function of these platesmight have been. Some ankylosaurs had tails stiffened by bony tendons thatterminated in a mace-like bony club. The largest of the stegosaurs weighedabout two-and-a-half tons and the largest of the ankylosaurs weighed aboutfour tons.

Marginocephalians are Cretaceous dinosaurs that have a bony extensionbeyond the rear or “margin” of the skull. They include two groups, thePachycephalosaurs and the Ceratopsians. Pachycephalosaur literally means“bone-head,” an apt description. These bipedal dinosaurs typically had askull of thickened bone adorned with spikes and tubercles. The utility ofsuch a skull can only be speculated upon. The largest species weighedbetween one and two tons. Ceratopsians were abundant in North Americaand many are also found in Asia, particularly Mongolia. They are rhinoceros-like, bulky quadripeds with immense heads that feature a frill of boneextending well over the neck. Many had horns either on the frill or protrudingfrom the face, above the eyes and on the snout. TRICERATOPS is the bestknown and largest of the Ceratopsians, weighing up to six tons. Large herdsof Ceratopsians were present during the late Cretaceous, and immensebone beds of species such as CENTROSAURUS have been unearthed alongthe Red Deer River in Alberta, Canada.

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1. What characteristics distinguish the two major groups of dinosaurs,Saurischia and Ornithischia?

2. Name and describe the various groups of dinosaurs found within theSaurischia and Ornithiscia?

Barrett, Paul. National Geographic Dinosaurs. Washington, D.C.: NationalGeographic Society, 1999.

Currie, Philip J., and Kevin Padian, eds. Encyclopedia of Dinosaurs. NewYork: Academic Press, 1997.

Dixon, Dougal. The Complete Book of Dinosaurs. London: HermesHouse, 2006.

Fastovsky, David E., and David B. Weishampel. The Evolution and Extinctionof Dinosaurs. 2nd ed. Cambridge: Cambridge University Press, 2005.

Norman, David. The Illustrated Encyclopedia of Dinosaurs. New York:Crescent Books, 1985.

Dino Data is a website involved in all aspects of dinosaur studies (requiresregistration) — http://dinodata.org/index.php

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ichard Owen, who coined the name “dinosaur,” wasimpressed by the large size of dinosaur bones. He recog-nized dinosaurs as reptilian but, from the few bones avail-able to him, he reconstructed them to appear more likemammals (such as a rhinoceros) than typical reptiles. Still,he never argued forcefully that they behaved as mammalsdo. As more dinosaur fossils were unearthed, ThomasHenry Huxley, the articulate and feisty defender ofDarwinism, suggested that dinosaur anatomy was like

that of warm-blooded, active animals, not sluggish reptiles. Huxley based partof his argument on a fossil of ARCHAEOPTERYX, the first bird. It was clear toHuxley that ARCHAEOPTERYX’s skeleton closely resembled that of small carniv-orous dinosaurs, animals that, in Huxley’s view, were adapted for high levelsof activity. Huxley’s assertions that dinosaurs might have been warm-bloodedand that birds might have evolved from dinosaurs, were largely forgotten formore than a century and dinosaurs were regarded metabolically as large ver-sions of iguanas and crocodiles. They were envisioned as cumbersome, slug-gish behemoths, living their Mesozoic lives in reptilian “slow motion.”

This view began to change in 1964 when Yale paleontologist John Ostrom dis-covered a small (about the size of a human) predatory dinosaur namedDEINONYCHUS (the name translates to “terrible claw”) in Montana. Ostrom’sdetailed study led him to draw a very different view of dinosaurs from what pre-vailed at the time. The anatomy of DEINONYCHUS was, in Ostrom’s opinion, thatof a rapidly-moving predator capable of sustained pursuit, a predator of greatagility. DEINONYCHUS had an enlarged sickle-like claw on its second toe and itsarticulation with the foot was such that the toe could be easily swung back andforth. It would have been ideal to eviscerate prey. The dinosaur’s arms werelong, its three-fingered hands very large and capable of rotation at the wrist.The tail was stiffened with bony tendons that kept it straight though it could beraised, lowered, or swiveled at the hip. The tail would have allowed the animalto balance while it maneuvered. From the fossils Ostrom excavated, he sug-gested that DEINONYCHUS may have hunted in packs and thus killed prey con-siderably larger than themselves. Fossil evidence for this possibility exists.

Ostrom suggested that such a dynamic anatomy was inconsistent with thatof typical ectotherms. In other words, he did not believe the animal couldhave functioned as a cold-blooded creature, but must have been warm-blood-ed to sustain a high activity level. Ostrom argued that DEINONYCHUS was likelyto have been endothermic, a suggestion that was soon enthusiasticallyembraced and amplified by his student, then still an undergraduate, RobertBakker (b.1945).

The Suggested Reading for this lecture is Robert T. Bakker’s TheDinosaur Heresies.

Lecture 10:Dinosaurs Become Dynamic

Bakker extended Ostrom’s idea of endothermy in DEINONYCHUS to encom-pass the entire diverse array of dinosaurs. Bakker believed that even thelargest dinosaurs, huge species such as BRACHIOSAURUS and APATOSAURUS,were endothermic, their physiology much more like that of an elephant orgiraffe than a tortoise or crocodile. Bakker’s articulate and persistent argu-ments in favor of dinosaur endothermy soon created intense debate, some ofit heated and contentious. As with all of science, from controversy comesresearch and from research comes knowledge. Ostrom and Bakker had, ineffect, created what has been described (by Bakker, though others firmlyagree) as a “Dinosaur Renaissance,” where morphology as well as thebehavior and ecology of dinosaurs has been seriously re-examined and, ingeneral, significantly revised. Bakker elaborated his arguments in favor ofdinosaur endothermy in a unique book, The Dinosaur Heresies (1986), thatwas readily accessible to lay readers, but was widely read, discussed, anddebated by professionals. Initially greeted by many professionals with strongskepticism, the argument that dinosaur physiology was more mammalianthan reptilian has gradually gained increasing acceptance.

There are several lines of argument that Bakker and others have put forth indefense of dinosaur endothermy. None has proven to be conclusive and theanswer to the question may not be one of unambiguous ectothermy orendothermy for all dinosaurs. Some dinosaurs were almost certainlyendothermic, but perhaps not all, perhaps not even most. There is a possible“middle ground” that may apply, where some dinosaurs may have maintaineda steady and high body temperature, but were not strictly physiologicallyendothermic, as mammals are.

Metabolism does not fossilize, nor does body temperature. What evidence isthere to examine? There are the fossils themselves. These consist mostly,but not entirely, of skeletons, and there are thousands of dinosaur bones andhundreds of articulated (or mostly articulated) skeletons. There is also fos-silized dinosaur skin and tendons, eggs and nests, tracks, and feces.Dinosaurs actually left quite a bit of information about themselves in the sedi-mentary rocks of the Mesozoic. What does this array of clues tell us?

The most obvious evidence for dinosaurs as active, mammal-like animalswas what, at least subconsciously, impressed Richard Owen and ThomasHuxley. It was also the basis of Ostrom’s argument regarding DEINONYCHUS.Dinosaurs are morphologically (meaning their body structure) more like mam-mals than they are like reptiles. Many, ranging from the chicken-sizedCOMPSOGNATHUS to the immense predatory GIGANOTOSAURUS were fullybipedal, presumably moving much like ostriches. Their center of gravity wasat the pelvis, with a long, muscular tail acting as a cantilever to the body andhead. The likely reason why TYRANNOSAURUS REX had extremely reduced fore-arms was that the weight reduction adapted the animal to compensate for theincreased anterior weight of the huge (up to about five feet long) head. Withlong legs and excellent weight balance, bipedal dinosaurs were capable oflengthy strides and efficient, sustained movement.

Among the quadripedal dinosaurs, particularly the sauropod giants such asAPATOSAURUS, their limbs were thick, positioned directly under their bodies,like those of elephants and hippos, not approaching right angles to the body,

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as is the case with alligators and lizards. Dinosaur giants balanced theirextreme weight atop their muscular legs and could walk easily for long dis-tances, much as elephant herds do today. Some of the larger quadripedaldinosaurs, such as TRICERATOPS, are thought to have even been capable ofgalloping, though this suggestion remains controversial. Such sustained andintensive activity requires a metabolism capable of supplying muscles withlarge amounts of oxygen, a metabolism typical of endotherms.

Following the revelations in Bakker’s thinking, it is interesting to considerwhy earlier depictions of dinosaurs misinterpreted their anatomy. Sauropodssuch as APATOSAURUS and large carnivores, such as TYRANNOSAURUS, wereshown dragging their tails. Both of these types of dinosaur actually held theirtails erect. Fossilized dinosaur tracks never show evidence of the tail drag-ging behind. Duck-billed dinosaurs such as IGUANODON and PARASAUROLOPHUS

were reconstructed to look like huge kangaroos, their long tails awkwardlybent. In reality they held their bodies horizontally as they moved, their tailsstiffened by bony tendons that ran throughout the neural spines of the verte-bral column. These erroneous reconstructions were largely the result of thesimple assumption that dinosaurs were “cold-blooded,” huge ectotherms thatwere incapable of the sorts of movement permitted by an endothermic metab-olism. After all, crocodiles and iguanas do drag their tails.

Overall, there is much about dinosaur anatomy to suggest active lifestyles,but that was overlooked because of the mindset that these animals were rep-tiles and must have functioned like crocodiles, turtles, and lizards. That notionis now essentially abandoned.

1. What led John Ostrom to reexamine the question of whether or not somedinosaurs may have been warm-blooded?

2. What arguments for dinosaur endothermy were put forth by Robert Bakkerand why is Bakker’s view known as a “dinosaur renaissance”?

Bakker, Robert T. The Dinosaur Heresies. New York: Zebra Books, 1986.

Bakker, Robert T. Raptor Red. New York: Bantam Books, 1995.

Desmond, Adrian J. The Hot-Blooded Dinosaurs: A Revolution in Paleontology.New York: Dial Press, 1976.

An interview with Dr. Robert T. Bakker in which he discusses the “DinosaurRenaissance” — http://www.geocities.com/stegob/robertbakker.html

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harles Darwin published On the Origin of Species in 1859.One immediate objection to Darwin’s argument for gradualevolution was that there are no obvious “missing links.”But in 1860, just a year after the publication of Origin, asingle feather was found in a slab from a quarry inSolnhofen, Bavaria. The feather was from a creature thatlived around a tropical lagoon during the Jurassic, some150 million years ago. In every way, it appeared to be the

feather of a modern bird. And one year after that, a skeletonof a dinosaur-like animal about the size of a pigeon was found with clearimpressions of feathers from the same location. Richard Owen purchasedthe skeleton for the British Museum and described it as the first bird,ARCHAEOPTERYX LITHOGRAPHICA. Owen’s argument was simple: it may havelooked anatomically like a dinosaur, but it was a bird because it had feathersindistinguishable from those of modern birds.

Owen’s view was immediately challenged by his younger rival, ThomasHenry Huxley, who argued that the “urvogel,” as it was termed, was anatom-ically not a bird. He described the skeleton as that of a small dinosaursimilar to COMPSOG NATHUS. In short, here was Darwin’s missing link, a formthat links two major groups, in this case reptiles and birds. In Huxley’s view,birds were descended from dinosaurs and ARCHAEOPTERYX was the proof.Call it a bird if you want, but it was really a feathered dinosaur. Further,Huxley believed Owen was rejecting his argument mostly because Owenopposed Darwin’s theory and did not want to admit to a missing linkbetween dinosaurs and birds.

The matter of whether birds descended from dinosaurs rested unresolveduntil it was re-examined by Gerhard Heilmann (1859–1946) in an exhaustivestudy The Origin of Birds published in 1927. By then another even finerskeleton of ARCHAEOPTERYX (named ARCHAEORNIS at the time) had been foundat Solnhofen. Heilmann examined every detail and concluded that birds anddinosaurs were alike, bone for bone, in all critical details save one. Birds hada wishbone, or furcula (representing fused clavicles, the “shoulder bones”).No dinosaur fossil had ever been found with a furcula. Heilmann concludedthat dinosaurs had lost the furcula during their evolution. He believed thatonce a structure was lost, it was never re-evolved. Because dinosaurs hadlost their furculas, they could not have given rise to birds. Heilmann conclud-ed that the compelling resemblance between ARCHAEOPTERYX and smalltheropod dinosaurs must be an example of convergent evolution (when unre-lated forms develop similar adaptations) and that the origin of birds was to befound elsewhere in the fossil record.

The Suggested Reading for this lecture is Luis M. Chiappe’s GlorifiedDinosaurs: The Origin and Early Evolution of Birds.

Lecture 11:Dinosaurs Become Airborne

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That settled the matter until it was re-opened by John Ostrom in the mid-1960s, at the time when Ostrom was studying DEINONYCHUS. At that time,most paleontologists regarded the origin of birds to be somewhere within theearly archosaurs, perhaps in some distant line of thecodonts yet to be dis-covered. Ostrom, in a detailed re-examination of ARCHAEOPTERYX, revivedHuxley’s view that birds descended directly from theropod dinosaurs. Thisview accorded well with Ostrom’s and later Bakker’s assertions about warm-blooded, active dinosaurs.

Since that initial discovery of a single feather in 1860, nine other partial orrelatively complete ARCHAEOPTERYX fossils have been found, all from thesame general area. Thus the entire database is a mere ten specimens.

ARCHAEOPTERYX has always been controversial. Could it fly? If so, how welldid it fly? If not, could it glide efficiently? Did it live in trees or was it cursorial,running on the ground? If it did fly, how did flight evolve, from the “ground up”or from the “trees down”? The answers to none of the above questions isknown with any degree of real certainty, although most anatomists who havestudied the animal believe it was capable of sustained flight, though not nec-essarily on a par with that of modern birds.

What we do know about ARCHAEOPTERYX is this. Its jaws bore teeth, unlikethe toothless beaks of modern birds. Its braincase was smaller than modernbirds of comparable size, but large relative to comparably sized terrestrialdinosaurs. It had a long forearm with three fingers and its wrist had a uniquecarpal bone shaped sort of like a “half-moon,” so it is called the semilunatecarpal. This made its wrist dexterous, able to fold the wing. The hand waslarge, longer, in fact, than the forearm. Many bones were hollow, as is thecase with birds and theropod dinosaurs. The tail was long and feathered onboth sides, unlike modern birds that have a short, compressed series of ver-tebrae called a pygostyle to support the tail feathers. ARCHAEOPTERYX had atail like a dinosaur, but with feathers. It had a furcula, or wishbone, and itmost definitely was covered with feathers. In addition to these characters, ithad numerous other skeletal characters that are shared by one particulargroup of dinosaurs to be discussed shortly.

Following John Ostrom’s re-examination of ARCHAEOPTERYX and his con-tention that the bird-dinosaur relationship should be re-considered, JacquesGauthier, who specializes in phylogenetic systematics (cladistics) was one ofseveral to do just that. These analyses repeatedly showed that well over onehundred skeletal characters were held in common by ARCHAEOPTERYX and agroup of dinosaurs called dromaeosaur maniraptorans. Cladograms producedby these analyses showed ARCHAEOPTERYX clearly nested within one particulargroup of saurichian theropod dinosaurs, the dromaeosaurs. At least accordingto the cladists, it was indeed a dinosaur.

But what about the original problem of the furcula? Heilmann’s claim was thedinosaurs lacked furculas. But they did not. Since Heilmann’s study, noweight decades old, theropod dinosaurs with furculas have been unearthed,dinosaurs ranging from VELOCIRAPTOR to TYRANNOSAURUS. Theropod dinosaursmost certainly did have furculas, but the furcula is a small bone, even on a T.REX, and is apt to be lost. Thus it takes a remarkably complete specimen forthe furcula to be present. Heilmann’s difficulty is solved.

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What about feathers? Don’t feathers make birds unique? Did dinosaurs have feathers?

Feathers perform multiple functions: signaling devices, flight, and heat con-servation. Feathers are superb insulators and thus are essential to supportwarm-bloodedness (endothermy) in relatively small animals such as birds,just as hair does for mammals.

Though feathers are always associated with birds, indeed in the modern par-lance they basically define birds, the fossil record has revealed that they werenot confined to birds, as they are today. Various “non-avian dinosaurs” havebeen discovered with feathers. Feathers are not even confined to the immedi-ate clade that contains the birds. Therizinosaurs had feathers, at least some ofthem. And, as will be discussed in lecture thirteen, T. REX may have beenfeathered, at least when it was immature. In other words, feathers of varioussorts may have occurred widely among theropod dinosaurs. The apparentevolutionary linkage between birds and dinosaurs, the existence of feathers inmultiple dinosaur clades (all within the theropods), and the fact that feathersfunction in part as insulators strengthens the contention that at least amongthe small, active theropods such as DEINONYCHUS (a maniraptor), endothermywas likely. Thus the notion of warm-blooded dinosaurs is linked directly to theresearch suggesting that birds evolved from one dinosaur lineage.

Even now, not all professionals agree that birds evolved from dinosaurs. Allof the non-avian feathered dinosaurs are from the Cretaceous, afterARCHAEOPTERYX, which was late Jurassic. Thus if dinosaurs did give rise toARCHAEOPTERYX, that ancestral theropod dinosaur has yet to be discovered.Objections have also been raised about how flight might have evolved. Ifdinosaurs were ancestors to birds, did birds really evolve from runningdinosaurs, from the ground up? Many think such a scenario is unlikely, andtheropod dinosaurs were not generally known to inhabit trees.

However, many recent discoveries coming from places like Laioning, China,are adding strength to the hypothesis that birds are, in fact, descended fromdromaeosaurs. A dromaeosaur named Microraptor gui is fully feathered,including having its hind legs feathered similar to its wings. It was likelyarboreal, but the question of whether or not it could fly is unanswered.CAUDIPTERYX was a dinosaur with short arms that bore feathers, as did thetip of its long tail.

In June 2007, a paper published in the journal Nature reported a newspecies of dinosaur from Inner Mongolia that was described as “an enormousfeathered chicken.” The animal, GIGANTORAPTOR ERLIENENSIS, would havestood seventeen feet tall, able to look a T. REX in the eye, with a weight ofthree thousand one hundred pounds. It is by far the largest known member ofa group called oviraptors, known to have nested in a manner similar to birds.The dinosaur had a relatively small head, was toothless, but with a strongbeak-like mouth. It is suspected to have dined on fruits and other forms ofplant food. It may have taken small animals too.

In March 2007, a team of scientists published a paper in Nature that ana-lyzed the size of bone cells in dinosaurs and related that to bone-cell sizeamong living vertebrates. They found the bone-cell size in living vertebrates

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correlates closely with the size of the genome, the amount of genetic materialper cell. Dinosaur bone-cell size most closely resembles that of birds, leadingthe researchers to conclude that dinosaurs had small genomes, just as mod-ern birds do.

The question of bird ancestry remains open to some, but it is fair to say atthis point that the majority of vertebrate paleontologists and likely the majorityof ornithologists share the opinion that birds represent the one survivingbranch of what was once a dense evolutionary bush of the Dinosauria. Thefossil record has revealed a compelling anatomic similarity between birds andtheropod dinosaurs. Evidence also exists that some dinosaurs were warm-blooded, feathered, made nests, and brooded young, just as modern birds.

1. What characteristics of ARCHAEOPTERYX liken it to dinosaurs and why was itnonetheless considered to be a bird?

2. Why did Gerhard Heilmann reject classifying ARCHAEOPTERYX as a dinosaurand why was his view inaccurate?

Chiappe, Luis M. Glorified Dinosaurs: The Origin and Early Evolution of Birds.Hoboken, NJ: John Wiley & Sons, 2007.

Dingus, Lowell, and Timothy Rowe. The Mistaken Extinction: DinosaurEvolution and the Origin of Birds. New York: Freeman, 1997.

Heilmann, Gerhard. The Origin of Birds. Reprint. New York: Dover, 1972.

Shipman, Pat. Taking Wing: Archaeopteryx and the Evolution of Bird Flight.New York: Touchstone, 1998.

Organ, Chris L., Andrew M. Shedlock, Andrew Meade, Mark Pagel, and Scott V. Edwards. “Origin of Avian Genome Size and Structure in Non-Avian Dinosaurs.” Nature. Volume 446. Number 7132. pp. 180–184.March 8, 2007.

Xu, Xing, Qingwei Tan, Jianmin Wang, Xijin Zhao, and Lin Tan. “A GiganticBird-like Dinosaur from the Late Cretaceous of China.” Nature. Volume447. Number 7146. pp. 844–847. June 14, 2007.

The University of California Museum of Paleontology devotes a detailed arti-cle on the dinosaur-bird connection —http://www.ucmp.berkeley.edu/diapsids/avians.html

Websites to Visit

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inosaur bone is often sufficiently well preserved that histo-logical studies (for instance, details of cell structure)may be done on it. Examination of the fine structure ofbone from various dinosaurs shows features more typi-cal of mammalian and avian bone than of reptilianbone. It also shows rings of growth that are useful in

documenting the rate at which the animal grew and towhat age it lived. Dinosaurs such as APATOSAURUS had

what is called laminar, fibrolamellar bone, a kind of boneassociated with rapid vascularization (blood vessel presence) and growth.

The histological evidence suggests that a thirty-ton APATOSAURUS thathatched from an egg smaller than a volleyball is likely to have attained adultsize when it was a mere twenty years old. If an ectothermic metabolism ispresumed to have been the case, it would have taken about five times aslong for the creature to reach adulthood. Such a life history, where a centuryis required to attain reproductive age, is obviously unlikely.

Other characteristics of fossil bone suggest that dinosaurs of all sizes wereessentially homeothermic (able to maintain a relatively high and constantbody temperature). The ratio of oxygen-16 to oxygen-18 varies with bodytemperature and can be measured from fossil bones. Dinosaur bone has aratio typical of what is seen in mammals and birds, not reptiles.

One of Robert Bakker’s arguments in support of dinosaur endothermy wasbased on food chains. Endothermic (high metabolism) animals require farmore food per gram of body weight than do ectotherms. A community of preyanimals could sustain approximately five to ten times more ectothermic thanendothermic predators of similar body mass because ectothermy is so muchless costly per animal. As shown by Bakker, a standing crop of one hundredtons of prey animals would sustain forty tons of ectothermic Komodo dragonlizards (assuming each lizard weighed about three hundred thirty pounds).But one hundred tons of prey would only sustain two-and-a-half tons of threehundred thirty pound endothermic African lions.

Bakker argued that predatory dinosaurs such as ALLOSAURUS and TYRANNO -SAURUS are rare in fossil deposits relative to the abundance of herbivorousdinosaurs (prey). In Bakker’s analysis, the ratio of prey to predator is typicalof today’s endothermic-dominated ecosystems such as the African Serengeti.However, most dinosaur experts believe that there is simply too much uncer-tainty about relative dinosaur population sizes as revealed by the fossil recordto support Bakker’s claims.

The Suggested Reading for this lecture is Judith G. Scotchmoor, BrentH. Breithaupt, Dale A. Springer, and Anthony R. Fiorillo’s (eds.)Dinosaurs: The Science Behind the Stories.

Lecture 12:Dinosaurs as Living Animals

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Groups of fossilized dinosaur nests (representing several species) havebeen found along with eggs in several widely scattered locations. One well-known site is Egg Mountain in the Montana badlands, discovered by JackHorner (b. 1946). Horner and his colleagues have made a detailed study of afossilized nesting colony of MAIASAURA PEEBLESORUM, an ornithopod herbivo-rous dinosaur that lived during the late Cretaceous period, between seventy-three and eighty million years ago. The young dinosaurs grew quickly.Hatching size was about twenty inches, but they grew to a length of ten feetwithin one or two years, all the while remaining at the nest, almost certainlytended by parents. Adulthood was reached within eight years and the adultswere about twenty-three to thirty feet long and weighed between two to threetons. The growth rate of this species is typical of birds and mammals, notreptiles. It suggests a high metabolism typical of endothermy.

Studies of fossilized dinosaur tracks indicate that some dinosaurs apparentlymoved in herds and likely made seasonal migrations, especially thosespecies that inhabited polar regions.

Fossil dinosaurs from places such as Alaska, Antarctica, and Australia(which, in the Cretaceous period, was still partly below the Antarctic Circle)show that dinosaurs lived in regions subject to protracted darkness and possi-ble cold. It is difficult to reconcile such adaptiveness with a fully cold-bloodedphysiology. There are no extant reptiles that live within high polar regions, atleast not during the dark of the polar winter.

Some dinosaur experts do not believe all dinosaurs were warm-blooded orendothermic. If the large herbivorous dinosaurs were endothermic, how couldimmense creatures such as APATOSAURUS and BRACHIOSAURUS consume suffi-cient plant food to sustain their high metabolic rates? Not only would theyseemingly need to constantly feed but they would be very likely to have eatenthe landscape bare of plants. Would there have been sufficient plant food tosustain large populations of huge herbivores?

Another argument against endothermy is found in dinosaur skulls. Mammalsand birds have bones called turbinates in the nasal regions of their skulls.Turbinates support membranes that are essential for moisture conservation.Birds and mammals would dehydrate from the movement and subsequentevaporation of warm, moisture-laden air through their nostrils (during exhala-tion) if it were not for the turbinates, which recapture the moisture. Ecto -thermic reptiles lack turbinates and so, apparently, do dinosaurs, though theevidence in some dinosaur groups is not entirely clear. Certain groups showindications of what may have been turbinates (the bones are delicate and donot easily fossilize). But if dinosaurs lacked turbinates and were endothermic,why did they not dehydrate?

Many students of dinosaur anatomy have suggested that the large dinosaurswould not have evolved endothermy because large dinosaurs, by virtue of sizealone, were capable of maintaining a steady high body temperature. But how?

Large dinosaurs would have high volume relative to surface area and thusaccumulate metabolic heat. Simply by bulk alone, they would warm.

Calculations suggest that a dinosaur such as a MAIASAURUS had about fivetimes the metabolic rate of a Komodo dragon lizard and was essentially

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endothermic, just based on its bulk alone. Animals with large volume tend togain heat. This is well below the metabolic rate of a mammal of approximateequal weight. Extending the argument, small dinosaurs (nine to forty-fourpounds) would require metabolic rates ten times that of reptiles, rates typicalof mammals and small birds. These may indeed have been endothermic.Medium-sized dinosaurs (two hundred twenty to two thousand two hundredpounds) would need a metabolic rate of six to eight times that of reptiles, andlarge dinosaurs (four-and-a-half to eleven tons) would, like the MAIASAURUS

cited above, require a metabolism five times that of reptiles. The largest ofthe dinosaurs, the giant sauropods (twenty-two to eighty-eight tons) wouldhave metabolic rates only three to four times those of a reptile. This variationin metabolic rate based on dinosaur mass is called mesometabolism.

If dinosaurs did exhibit mesometabolism it would be age dependent in thosewith large body mass. A juvenile TYRANNOSAURUS would have a metabolismten times that of a reptile, a metabolism comparable to that of a mammal orbird. But by the time it reached adulthood, its metabolic rate would drop by atleast half.

The ecological implications of mesometabolism are striking. An animalsuch as a TRICERATOPS (six-and-a-half tons) would need only as much foodas a modern bison (eighteen hundred pounds). An APATOSAURUS would onlyneed as much food as a modern elephant to sustain itself. The terrestrialecosystems of the Mesozoic would not have been energetically much differ-ent from those throughout the Cenozoic, when mammals became the domi-nant large animals.

1. How do scientists estimate how rapidly dinosaurs grew to adult size?

2. Why might some of the largest dinosaurs have not been fully endothermic?

Scotchmoor, Judith G., Brent H. Breithaupt, Dale A. Springer, and Anthony R.Fiorillo, eds. Dinosaurs: The Science Behind the Stories. Alexandria, VA:American Geological Institute, 2002.

Colagrande, John, and Larry Felder. In the Presence of Dinosaurs.Alexandria, VA: Time-Life, 2000.

Horner, John R. Dinosaur Lives. San Diego: Harcourt Brace, 1997.

Psihoyos, Louie. Hunting Dinosaurs. New York: Random House, 1994.

1. The National Geographic Society provides a detailed site discussing dino -saur eggs, including the virtual “hatching” of several types of dinosaurs — http://www.nationalgeographic.com/dinoeggs

2. The Stone Company of Boulder, CO, provides a good general discussionabout dinosaur eggs by dinosaur enthusiast Florence Magovern —http://www.stonecompany.com/dinoeggs/study/eggstudy.html

Websites to Visit

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he most infamous of the dinosaurs is, of course,TYRANNOSAURUS REX, star attraction at museums, bestsupporting dinosaur in the original King Kong, and

deserving of an Oscar for its stellar performance inJurassic Park. Who can forget that final scene when the

T. REX hurls a VELOCIRAPTOR against a dinosaur skeleton,crumbling it, and turns and lets out a final, climactic roar, as abanner falls saying “When Dinosaurs Ruled the Earth.”

Since its initial discovery near Hell Creek, Montana, about a century ago, approximately thirty partial or nearly complete skeletons of T. REX have been unearthed. Thus paleontologists have a sound understand-ing of its anatomy. Some of the most complete T. REX skeletons are evennamed, such as the famous “Sue,” for Susan Hendrickson, who first found it.This skeleton was the focus of a protracted legal battle and was eventuallyauctioned by Sotheby’s for 8.36 million dollars. The dinosaur is on exhibit atthe Field Museum of Natural History in Chicago. Other T. REX names include“Stan,” “Duffy,” “Bucky,” “Peck’s rex,” and “Black Beauty.”

T. REX has been historically depicted as walking upright, its head high in theair, its tail dragging behind it. This inaccuracy was recently corrected, result-ing in the literal deconstruction and reconstruction of T. REX specimens atvarious museums, including at the American Museum of Natural History. Inreality, T. REX held its body horizontally, its dense muscular tail balancing itsforward body with the center of gravity just in front of the hips. The unusuallysmall arms that characterized T. REX may have been an adaptation toreduce its forward weight. In any case the arms, with two-fingered hands,were strong and functional, the bones showing large muscle scarring.Perhaps its arms aided the animal in rising from the ground, as, when resting, it would have squatted like a rooster.

The largest of the T. REX specimens has been estimated to weigh as muchas seven tons, though extrapolated dinosaur body weights are difficult toknow with great precision. The massive skull is nearly five feet in length. Theskull is unusual in that it is much wider from the eyes to the rear than in frontof the eyes. Thus the orbits (eye sockets) are positioned such that a T. REX

must have had stereoscopic vision. Teeth were serrated, chisel-like, and con-ical, not blade-like as in allosaurs. A T. REX could easily crush bone with itsmassive teeth and incredible jaw strength. Its long snout plus reconstructionsof its brain anatomy (based on casts made from various skulls) show that T.REX had, like many dinosaurs, a very well developed olfactory sense. BobBakker has reported the presence of turbinate bones in the snout, which

The Suggested Reading for this lecture is John R. Horner and DonLessem’s The Complete T. Rex.

Lecture 13:T. REX Deconstructed and Reconstructed

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would indicate a very keen sense of smell. Further, its inner ear was very welldeveloped both for balance and for hearing. Likely its olfaction, vision, andhearing were all quite excellent.

The legs were massive, particularly the dense thigh muscles. Like virtuallyall theropods, T. REX walked on three toes. The thigh bone (femur) was rela-tively long compared with the rest of the leg and foot and this indicates that T.REX did not run fast relative to its size. Computer studies modeling the gait ofTYRANNOSAURUS REX indicate that it may have moved quickly as a juvenile but,because of its immense body size and overall bulk, it slowed considerably bythe time it was a full-grown adult. Other studies based on extrapolations fromthe musculature of crocodilians and chickens indicate that to run as fast asforty-five miles per hour, a T. REX would have to have anywhere from 40 to 86percent (depending on the mathematical model used) of its body mass in itslegs, clearly impossible. Unlike the sprinting, jeep-chasing “roadrunner fromHell” depicted in the first Jurassic Park film, an adult T. REX likely moved nofaster than fifteen to twenty-five miles per hour. Its normal walking wouldhave been about eleven miles per hour, still a pretty good pace. But any jeep,or, for that matter, a skilled biker, could outrun it. Moving as fast as twenty-five miles per hour would have posed risks for a large T. REX, because if ithappened to fall, its very bulk could cause it to sustain lethal injuries.

T. REX grew to adulthood quickly. From an analysis of growth-lines in numer-ous T. REX bones, researchers have concluded that a T. REX reached fulladult size by age twenty and likely lived for no more than about twenty-eightyears. Given that an adult conservatively weighed about five-and-a-half tons,the animal grew at a rate of just under five pounds per day. It is difficult toimagine such a rapid growth rate in a cold-blooded animal. No modern reptileapproaches such a rapid growth rate, but birds do.

Enough fossil skeletons of ALBERTOSAURUS (a tyrannosaur species somewhatmore light in weight and more slender than T. REX) were recovered from aseventy-million-year-old site north of Calgary to permit scientists to analyzeage-related survivorship. Using bone growth line counts to establish age, theyfound that juvenile animals between two and thirteen had high survivorship(with an annual mortality rate of only about 3.5 percent), but after age thirteenlife must have become riskier. Between fourteen and twenty-three, the annualdeath rate rose to 22.9 percent and virtually none of the animals survivedbeyond age twenty-eight.

Bone studies even make it possible to identify the sex of a T. REX specimen.In one fossil, unusually well preserved tissue inside the marrow cavityappears identical to a certain kind of bone called medullary bone found onlyin female birds. If T. REX bone is indeed medullary bone, it not only showsthat the animal in question was a female, but also supports the evolutionarylinkage between dinosaurs and birds. In the spring of 2007, studies alsoreported that the protein collagen had been recovered from within the thighbone (femur) of a T. REX. Seven amino acid sequences of the collagen wereisolated and five of the seven were identical to those found in chickens, addi-tional support for the relationship between birds and theropod dinosaurs.

T. REX inhabited North America at the end of the Cretaceous. It was not theonly tyrannosaur present. As mentioned above, a more gracile species,

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Albertosaurus sarcophagus, is found abundantly in places such as the RedDeer River in southern Alberta. Two other tyrannosaur species, Gorgosauruslibratus and Daspletosaurus torosus, are both commonly found in variousplaces in western North America. And in Asia, there was a species quite simi-lar to T. REX, TARBOSAURUS BATAAR. In addition, other dinosaurs have beenfound that are cladistically nested within the tyrannosaurs. One of these isDilong paradoxus, first described in 2004. DILONG is from the early Cretaceousin China and was small and gracile. It had long arms with three-fingeredhands. Most interesting is that one specimen appears to be covered with fila-mentous structures thought to be primitive feathers. This discovery has led tothe suggestion that a juvenile T. REX may also have been covered by someform of feathers, likely for heat retention. Given its great bulk, it is highlydoubtful that an adult would have been feathered. Yet another unique tyran-nosaur was GUANLONG WUCAII, from the late Jurassic in China. This early butamazing tyrannosaur was adorned with an elaborate bony head crest.

Dinosaur expert Jack Horner has argued that T. REX was too large to functionefficiently as a predator and must, instead, have scavenged for carcasses.Was T. REX a giant vulture? The species lived at a time when immense herdsof herbivorous Ceratopsians and Hadrosaurs were present and there wouldlikely have been many carcasses to be scavenged. The large size of a T. REX would have made it easy for the animal to displace other scavengers at a carcass unless, of course, they also happened to be largetyrannosaurs. The keen olfactory sense would have been adaptive for locatingcarcasses. The powerful jaws and rounded, chisel-like teeth were ideal fortearing into flesh and crushing bones. A T. REX was well adapted to eat a car-cass, bones included.

On the other hand, there is no reason why a T. REX could not have easilykilled or mortally wounded a living animal if it could get its powerful jaws on it.A T. REX may have functioned as an ambush predator, picking on sick orinjured prey that were unable to move quickly. The teeth of T. REX were ser-rated and, like those of other theropods, were constantly being lost andreplaced. The jaws had a prominent overbite. It is quite likely, as is the casewith Komodo dragon lizards, that septic bacteria thrived in the bits and piecesof flesh trapped among the jagged teeth and that the very bite of a T. REX

would eventually prove to be lethal due to bacterial infection. Thus a T. REX

need only have bitten its prey to deliver what would prove a mortal wound. Itwould then merely follow it until it died. Thus predation and scavenging arenot mutually exclusive at least in the case of T. REX.

Scavenging among Tyrannosaurs would have likely been age related.Juvenile and small animals would have been less likely to prevail at a car-cass when larger animals were present. Likewise, juvenile and small animalswere likely faster and better adapted to safely pursue and subdue live prey.Thus it is possible that as it aged, a T. REX would gradually shift from mostlypredatory to mostly scavenging.

There is some paleontological evidence that T. REX associated with others ofits species in packs. Many specimens show facial wounds that look to havebeen inflicted by other tyrannosaurs. Groups of tyrannosaurs may have fol-lowed migrating herds of plant eaters and either combined in killing them or,perhaps more likely, competed for access to carcasses.

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Although many other dinosaurs have been described, including huge preda-tors such as SPINOSAURUS and GIGANOTOSAURUS, there is still nothing quitecomparable to a T. REX. The scene in the second Jurassic Park film thatshows T. REX terrorizing downtown San Diego is amusing, but at the sametime sobering. The proportions are correct. This is an animal that could lookdirectly into a second- story window and was, in fact, larger than a bus. Itmay not be a bad thing that, as fascinating as a T. REX must have been, it isnow extinct.

1. How have paleontologists discovered the probable longevity and calculatedthe speed of T. REX?

2. What arguments have been made for T. REX being a scavenger rather thana predator? Why might it have been both?

Horner, John R., and Don Lessem. The Complete T. rex. New York:Touchstone, 1993.

Larson, Peter, and Kristin Donnan. Rex Appeal. Montpelier, VT: InvisibleCities Press, 2004.

Paul, Gregory S. Predatory Dinosaurs of the World. New York: Simon &Schuster, 1988.

1. The American Museum of Natural History features a study of T. REX —http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Tyrannosaurus/tyrannos.html?dinos

2. The Field Museum provides several pages about Sue the T. REX —http://www.fieldmuseum.org/sue

Websites to Visit

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he question I am asked more than any other aboutdinosaurs is, What killed them? The large dinosaurs thatso fascinate us are all long gone, a fact that has pro-duced no shortage of suggestions as to why. A perusal

of my many dinosaur books, some dating back over a half-century, shows that the most repeated explanation is “cli-

mate change.” Details about just how the climate changed arerarely supplied. Other ideas range widely and include suchnotions as exploding stars, egg-eating mammals, lousy

parental care, and terminal constipation brought about by devouring newlyevolved flowering plants.

What killed the dinosaurs? There is no simple answer because dinosaursexisted for one hundred sixty million years and in that vast period of time newspecies continuously evolved and other species went extinct. Based on theaverage species longevity of extant animals comparable to dinosaurs, the esti-mate is that a given species of dinosaur might have been around for anywherefrom three to five million years. STEGOSAURUS STENOPS, the stegosaur commonin the late Jurassic in North America, was extinct for at least seventy millionyears before T. REX evolved! That’s a time period longer than the entire Ceno -zoic Era, the period from sixty-five million years ago to the present, when mod-ern mammals have dominated the planet. Needless to say, STEGOSAURUS andT. REX never met. So all the dinosaurs did not go extinct at once. Far from it.

Paleontologists recognize different patterns of extinction. There is back-ground extinction, where a single species becomes extinct while others donot. This sort of process is relatively constant, and is, of course, compensat-ed (though not necessarily balanced) by ongoing speciation. There are minorextinction events, such as the one that closed out the Jurassic period, wherenumbers of species become extinct approximately at the same time. Andthere are the five major extinction events (Ordovician, Devonian, Permian,Triassic, and Cretaceous) that have resulted in major losses of multiplespecies and essentially redirected patterns of evolution. T. REX appears tohave been a victim of a mass extinction event, the “K/T Event,” that endedthe Mesozoic and began the Cenozoic. Had that event not occurred, thediversification of mammals and the subsequent evolution of our own speciesis questionable at best.

There should be no surprise that dinosaurs were undergoing variousdegrees of extinction since they first evolved in the late Triassic. The worldchanged considerably over the 160 million years when dinosaurs dominatedterrestrial ecosystems. Continents became rearranged such that climate and

The Suggested Reading for this lecture is Walter T. Alvarez’s T. Rex andthe Crater of Doom.

Lecture 14:The Cretaceous Extinction Event

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sea-level changes happened, new ocean basins formed, and some continen-tal masses became totally isolated from others. The rearrangement of land-masses may have had negative impacts on certain dinosaurs for reasonsranging from major changes in temperature and precipitation to increasedinterspecies competition and predation. During the Cretaceous period, flower-ing plants ranging from magnolias and sycamores to various grassesevolved, and with them we see changes in dinosaurs. Long-neckedSAUROPODS become less numerous as dinosaurs with more effective chewingcapabilities such as HADROSAURS and CERATOPSIANS become diverse andabundant. A similar pattern is easily observed for large mammals if one fol-lows their extinction patterns through the sixty-five million years of theCenozoic. As forests shrink and grasslands spread, as equitable climatesbecome more seasonal, patterns of mammal diversity shift. New mammalsspecialized for grazing evolve and others become extinct.

The dinosaur extinction question is not usually about anything other than theMesozoic coup de grace, the so-called Cretaceous extinction event. Thiswas, after all, one of the five major extinctions. So for the remainder of thislecture, that will be the focus.

A new book to be released in 2007 with the intriguing title What Bugged theDinosaurs suggests that proliferation and diversification of biting insects dur-ing the Cretaceous may have had negative impacts on dinosaurs. Insects arevectors for serious diseases and many ecologists are re-examining howinsects and the diseases they spread may affect evolutionary patterns amongvertebrates. Some paleontologists argue that dinosaurs were in decline, atleast regarding species diversity, as the Cretaceous drew to an end. Perhapsinsect-borne diseases had some role in such a decline, although other pale-ontologists argue that their data do not show dinosaur decline before theabrupt end of the Cretaceous. That question remains open.

But one thing is certain and that is that the Cretaceous mass extinction affect-ed far more animal groups than dinosaurs. Whatever happened also resultedin mass extinctions of oceanic zooplankton called foraminiferans. They are notvery much like dinosaurs. And, as well, all ammonites, which were marinecephalopod mollusks similar to today’s chambered nautilus, became extinct.And before leaving the seas, note that all plesiosaurs, ichthyosaurs, andmosasaurs failed to survive the Cretaceous. On land, in addition to dinosaurs,all of the pterosaurs, some with immense wing-spans, also suffered totalextinction. On the other hand, groups such as turtles, frogs and other amphib-ians, snakes and lizards, crocodilians, modern birds, and mammals all passedthrough the extinction filter. Why did they survive when dinosaurs and othergroups did not? In other words, the Cretaceous extinction event looks to havebeen selective. Such selectivity demands explanation.

Two prominent hypotheses to assign cause to the Cretaceous extinctionemerged over the past three decades. They are not mutually exclusive and,in concert or individually, could have had devastating effects. These hypothe-ses are (1) extreme volcanic activity inducing catastrophic global climatechange and (2) the impact of a six-mile-wide asteroid in the area of theYucatan Peninsula. There is little doubt that both of these possible causesreally did happen. What is debated is the actual ecological effects of each.

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Looking first at volcanism, there is strong evidence for sustained and exten-sive volcanic activity at the end of the Cretaceous at an area known as theDeccan traps in India. The word “Deccan” refers to “southern” in Sanskrit andthe word “trap” means “staircase” in Dutch, for the step-like appearance ofthe lava flows. The Deccan Traps were immense. In some areas, the thick-ness is five hundred feet and in western India there is evidence of an eightthousand foot thick lava flow. At its height, a total of seven hundred seventy-two thousand square miles may have been covered, lava continuouslyextruding from active volcanos. The immensity of this volcanic activity wouldhave produced dramatic global climatic effects. Dating the age of the flowshas proven somewhat difficult, but evidence now suggests that the volcanismwas in the Maastrichtian epoch, beginning a few million years before the endof the Cretaceous. The climatic effects of extensive volcanism would havebeen similar to that of asteroid impact to be discussed next.

Evidence of asteroid impact was first published in 1980 by a team headedby Luis and Walter Alvarez, father and son. They were not investigatingdinosaur extinction. Rather, they were attempting to explain the origin of aunique clay layer at the Cretaceous/Tertiary (K/T) boundary. The thin line ofclay was extraordinarily high in the element Iridium, a rare element on Earthbut common in asteroids and meteorites. The odd red and green clay wassoon found in other regions at the K/T boundary. It appeared to be global inextent. The clay was shown to contain “shocked quartz,” a form of quartz withfine lines that only happens during impacts or nuclear explosions. Also foundwere tektites, small, black, glassy beads that form with impacts. Radiometricdating of the tektites indicates an age of 65.01 million years, precisely at theK/T boundary. The asteroid impact theory was highly controversial when firstput forth, but evidence mounted in its favor when the site of the proposedimmense crater was found.

In 1990, Alan Hildebrand, after dogged detective work, published the loca-tion of the crater just off the northern tip of the Yucatan Peninsula. He namedit Chicxulub. The Mayan name is taken from a nearby village, and means “tailof the devil.”

The entire crater is some one hundred twenty-five miles across and there isnow no doubt of its existence nor any doubt of its age, at the K/T boundary.The crater was made by the impact of an asteroid about six miles in diame-ter striking at an estimated speed of thirty-one thousand miles per hour onan oblique angle that spewed masses of material toward North America. Itwould have made a crater thirty miles in diameter within the first ten secondsof impact and that crater would eventually be greater than one hundredmiles in diameter.

The impact, subsequent shock wave, and debris would have resulted incalamitous global fires, dense and protracted clouding of the atmosphere, andpossibly intense acid rain. In short, it would produce catastrophic disruption infood webs. Small animals may have been able to avoid the worst effects bet-ter than the large dinosaurs simply by taking shelter, but many questionsremain about how, for example, such sensitive animals as frogs could haveescaped the effects of acid rain. Questions also remain about exactly howlong climatic effects would last and exactly what they might have been.

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Regardless, it appears that the last of the dinosaurs went out with a bang,perhaps the victims of a one-two punch, volcanism and extra-terrestrialimpact. What a way to go!

Dinosaurs such as STEGOSAURUS and T. REX will never return, but they willlikely always fascinate us. Go see their remains and those of other dinosaursin museums, visit some sites where their fossils have been found, and thinkback on what they must have been like in their world. And should you want tosee any live dinosaurs, just put out a bird feeder.

1. What are the two most prominent hypotheses for explaining theCretaceous extinction?

2. How does the K/T boundary provide evidence for an immense asteroid impact?

Alvarez, Walter T. T. Rex and the Crater of Doom. Princeton: PrincetonUniversity Press, 1997.

Poinar, George, Jr., and Roberta Poinar. What Bugged the Dinosaurs?:Insects, Disease, and Death in the Cretaceous. Princeton, NJ: PrincetonUniversity Press, 2007.

Raup, David M. Extinction: Bad Genes or Bad Luck? New York: W.W.Norton, 1991.

1. The University of California Museum of Paleontology features an article byRichard Cowen entitled “The K-T Extinction” —http://www.ucmp.berkeley.edu/education/events/cowen1b.html

2. Dr. Ken Hooper’s website Virtual Paleontology Museum (Ottawa-CarletonGeoscience Centre and Department of Earth Sciences Carleton University,Ontario, Canada) features a thorough discussion of the K/T event —http://park.org/Canada/Museum/extinction/tablecont.html

3. The University of Arizona, Department of Planetary Sciences websiteChicxulub Impact Event features a detailed analysis of the impact —http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Chicx_title.html

Websites to Visit

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The following books provide an excellent supplement to the lectures found inthis course:

Farlow, James O., and M.K. Brett-Surman, eds. The Complete Dinosaur. Bloomington,IN: Indiana University Press, 1997.

Kricher, John. Peterson First Guide to Dinosaurs. Boston: Houghton Mifflin, 1990.

Norman, David. Dinosaur! New York: Macmillan, 1991.

Paul, Gregory S., ed. The Scientific American Book of Dinosaurs. New York: St.Martin’s Griffin, 2000.

Two technical books will be of use to those seeking more advanced material:

Glut, Donald F. Dinosaurs: The Encyclopedia. Jefferson, NC: McFarland &Company, 1997.

Weishampel, David B., Peter Dodson, and Halszka Osmolska, eds. TheDinosauria. 2nd ed. Berkeley: University of California Press, 2004.

Suggested Readings:

Alvarez, Walter. T. Rex and the Crater of Doom. Princeton: Princeton UniversityPress, 1997.

Bakker, Robert T. The Dinosaur Heresies. New York: Zebra Books, 1986.

Barrett, Paul. National Geographic Dinosaurs. Washington, D.C.: National GeographicSociety, 1999.

Chiappe, Luis M. Glorified Dinosaurs: The Origin and Early Evolution of Birds.Hoboken, NJ: John Wiley & Sons, 2007.

Colbert, Edwin H. The Age of Reptiles. Reprint. Mineola, NY: Dover, 1997.

Gould, Stephen Jay, ed. The Book of Life. New York: W.W. Norton, 2001.

Horner, John R. Digging Dinosaurs. New York: Workman Publishing, 1988.

Horner, John R., and Don Lessem. The Complete T. rex. New York: Touchstone, 1993.

McGowan, Christopher. The Dragon Seekers: The Discovery of DinosaursDuring the Prelude to Darwin. London: Little, Brown, 2001.

Norell, Mark A., Eugene S. Gaffney, and Lowell Dingus. Discovering Dinosaurs in theAmerican Museum of Natural History. New York: Alfred A. Knopf, 1995.

Sanz, Jose Luis. Starring T. Rex!: Dinosaur Mythology and Popular Culture.Bloomington, IN: Indiana University Press, 2002.

Scotchmoor, Judith G., Brent H. Breithaupt, Dale A. Springer, and Anthony R. Fiorillo,eds. Dinosaurs: The Science Behind the Stories. Alexandria, VA: AmericanGeological Institute, 2002.

Wallace, David Rains. The Bonehunters’ Revenge. Boston: Houghton Mifflin, 1999.

Wilford, John Noble. The Riddle of the Dinosaur. New York: Alfred A. Knopf, 1985.

Other Books of Interest:

Bakker, Robert T. Raptor Red. New York: Bantam Books, 1995.

Benton, Michael J. Vertebrate Paleontology. 3rd ed. Malden, U.K.: Blackwell, 2005.

Berry, Mark F. The Dinosaur Filmography. Jefferson, NC: McFarland andCompany, 2002.

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Other Books of Interest (continued):

Bird, Roland T. Bones for Barnum Brown. Fort Worth, TX: Texas Christian UniversityPress, 1985.

Burnie, David. The Kingfisher Illustrated Dinosaur Encyclopedia. New York:Kingfisher, 2001.

Cain, Dana, and Mike Fredericks. Dinosaur Collectables. Norfolk, VA: Antique TraderBooks, 1999.

Cloudsley-Thompson, J.L. Ecology and Behavior of Mesozoic Reptiles. Heidelberg:Springer, 2005.

Colagrande, John, and Larry Felder. In the Presence of Dinosaurs. Alexandria, VA:Time-Life, 2000.

Colbert, Edwin H. Dinosaurs: An Illustrated History. Maplewood, NJ: Hammond,Inc., 1983.

———. The Great Dinosaur Hunters and Their Discoveries. Reprint. New York:Dover, 1984.

Currie, Philip J., and Kevin Padian, eds. Encyclopedia of Dinosaurs. New York:Academic Press, 1997.

Czerkas, Sylvia J., and Stephen A. Czerkas. Dinosaurs: A Global View. New York:Mallard Press, 1991.

Czerkas, Sylvia Massey, and Donald F. Glut. Dinosaurs, Mammoths, and Cavemen:The Art of Charles R. Knight. New York: E.P. Dutton, Inc., 1982.

Debus, Allen A., and Diane E. Debus. Paleoimagery: The Evolution of Dinosaurs in Art.Jefferson, NC: McFarland and Company, 2002.

de Camp, L. Sprague, and Catherine Cook de Camp. The Day of the Dinosaur. NewYork: Doubleday & Company, 1968.

Desmond, Adrian J. The Hot-Blooded Dinosaurs: A Revolution in Paleontology. NewYork: Dial Press, 1976.

Dingus, Lowell, and Timothy Rowe. The Mistaken Extinction: Dinosaur Evolution andthe Origin of Birds. New York: Freeman, 1997.

Dixon, Dougal. The Complete Book of Dinosaurs. London: Hermes House, 2006.

Fastovsky, David E., and David B. Weishampel. The Evolution and Extinction ofDinosaurs. 2nd ed. Cambridge: Cambridge University Press, 2005.

Fortey, Richard. Life: A Natural History of the First Four Billion Years of Life on Earth.New York: Vintage Books, 1997.

Gallenkamp, Charles. Dragon Hunter: Roy Chapman Andrews and the Central AsiaticExpeditions. New York: Viking, 2001.

Glut, Donald F. The Dinosaur Scrapbook. Secaucus, NJ: Citadel Press, 1980.

Heilmann, Gerhard. The Origin of Birds. Reprint. New York: Dover, 1972.

Horner, John R. Dinosaur Lives. San Diego: Harcourt Brace, 1997.

———. Dinosaurs Under the Big Sky. Missoula, MT: Mountain Press, 2001.

Lanham, Url. The Bone Hunters. New York: Columbia University Press, 1973.

Larson, Peter, and Kristin Donnan. Rex Appeal. Montpelier, VT: Invisible CitiesPress, 2004.

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Other Books of Interest (continued):

Lessem, Don. Dinosaurs Rediscovered. New York: Touchstone, 1992.

Norman, David. The Illustrated Encyclopedia of Dinosaurs. New York: CrescentBooks, 1985.

———. Prehistoric Life and the Rise of the Vertebrates. New York: Macmillan, 1994.

Novacek, Michael. Dinosaurs of the Flaming Cliffs. New York: Doubleday, 1996.

Ostrom, John H., and John S. McIntosh. Marsh’s Dinosaurs. New Haven: YaleUniversity Press, 1966.

Paul, Gregory S. Predatory Dinosaurs of the World. New York: Simon &Schuster, 1988.

Poinar, George, Jr., and Roberta Poinar. What Bugged the Dinosaurs?: Insects,Disease, and Death in the Cretaceous. Princeton, NJ: Princeton UniversityPress, 2007.

Psihoyos, Louie. Hunting Dinosaurs. New York: Random House, 1994.

Rainger, Ronald. An Agenda for Antiquity: Henry Fairfield Osborn and VertebratePaleontology at the American Museum of Natural History, 1890–1935. Tuscaloosa,AL: University of Alabama Press, 1991.

Raup, David M. Extinction: Bad Genes or Bad Luck? New York: W.W. Norton, 1991.

Reader, John. The Rise of Life: The First 3.5 Billion Years. New York: Alfred A.Knopf, 1986.

Shipman, Pat. Taking Wing: Archaeopteryx and the Evolution of Bird Flight. New York:Touchstone, 1998.

Sternberg, Charles Hazelius. Hunting Dinosaurs in the Bad Lands of the Red DeerRiver, Alberta, Canada. Edmonton: NeWest Press, 1985.

Webber, Roy P. The Dinosaur Films of Ray Harryhausen. Jefferson, NC: McFarlandand Company, 2004.

Wallace, Joseph. The American Museum of Natural History’s Book of Dinosaurs andOther Ancient Creatures. New York: Simon & Schuster, 1994.

These books are available online through www.modernscholar.com or by calling Recorded Books at 1-800-636-3399.