Eyewitness II; #111; Dinosaur

This o-- [silence] [silence] [countdown leader] Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual financial support from viewers like you. [theme music] Tyrannosaurus rex. The largest meat eater ever to walk the earth.

One of the hundreds of dinosaurs that have been reconstructed and, well, not exactly brought back to life. Dinosaurs only come back to life in the movies and they've been dead for 64 million years before humans appeared on Earth. Or on the menu. If anything, it's been the human imagination that's fed on dinosaurs. With taste ranging from green and comic, to the global and serious game of paleontology. Since the first dinosaur fossils were identified almost 200 years ago it's been science that's fueled science fiction. The evidence on earth by paleontology, the study of fossils and ancient life forms, has given new life to the dinosaur and set them roaming across the landscapes of our imagination. [musical fanfare] And with a new fossil being discovered about every seven weeks, our knowledge of dinosaurs

is growing by leaps and bounds. Where did the name dinosaur come from? Sir Richard Owen rode into history when he declared that the fossils of giant animals being discovered in England in the early 1800s should be called Dinosauria, meaning "terrible lizards." Why lizards? We know dinosaurs were similar to reptiles because fossils have revealed that they had scaly skin and laid eggs. It's the dinosaur body plan which sets them apart from the reptiles. 250 million years ago the reptile design of the day incorporated the short sprawling legs of the lizard and the short bent-kneed legs of ancient crocodiles. Dinosaurs evolved because of a breakthrough in leg design. Dinosaur legs were longer and tucked under the body. And this breakthrough came in both four and two legged models. Dinosaurs could not only stand up, they could run faster than anything

else around. This ability to pursue or escape pursuit was a major factor in the dinosaurs' success. T. rex enjoyed its success by eating its own weight in meat every week. That's seven tons or the equivalent of 12 cows. The first T. rex found wasn't called Tyrannosaurus rex. When Barnum Brown, known as Mr. Bones because he found so many dinosaurs, dug up the first T. rex in 1900 he identified it as a large meat eater. And called it Dynamosaurus imperiosus. But Dynamosaurus imperiosus, an overnight sensation in the world of paleontology, would soon change its name to something more befitting the largest meat eater ever to kill for a living. Tyrannosaurus rex, literally "tyrant lizard king." [growling] People have been finding dinosaur bones all over the world for 2000 years,

people like the Chinese who've always called them dragons. The first known dinosaur extinction theory is attributed to the third century writer Chang Qu who explained the mystery of dinosaur bones by writing, "A dragon ascended a mountain and went directly to the gate of heaven. The gate being locked, the dragon fell back to earth and died at this spot. Later, it sank into the earth." Although we may never be able to completely answer the why of dinosaur extinction we do know the when. 225 million years ago, when dinosaurs first appeared, the Earth was a very different place. All the land was joined together in one super continent called Pangaea. For the next 160 million years dinosaurs dominated the earth.

To get an idea of this immense time scale, imagine a book 225 pages long, each page equal to one million years. Dinosaurs would be the main characters for the first 160 pages. Mammals would take over for the last third of the book. Humans wouldn't appear until the top of the last page, one million years ago. And it wouldn't have been until the bottom of the last page that we even knew dinosaurs existed. When the second T. rex was found in 1902, a large foreleg found nearby was believed to belong to it. It wasn't until 88 years later, in 1990, when the 10th T. rex was excavated, that paleontologists realized Mr. Bones got it wrong. It wasn't the first mistake made in piecing together a dinosaur. And it won't be the last. When the freshest evidence to be found has been dead for

65 million years, it's no wonder paleontology has a long tradition of getting things wrong. One of the first bloopers occurred in England in 1820. Dr. Gideon Mantell found some fossilized teeth, And excavated Iguanodon, named after the modern-day iguana. Iguanodon might be considered the beginning of Dino-mania. It was such a hit with the English public that a full-scale model was built in Crystal Palace Park. Before the model was finished, a dinner party was held inside it for 20 people. The diners are long gone but the Iguanodon model is still there, A monument to the pitfalls of paleontology. What Mantell assumed to be a nose horn turned out to be a thumb spike on the Iguanodon's multipurpose hand. But Mantell's Iguanodon is just one example from over 1000 dinosaur finds scattered across all the continents,

A tiny fraction of the billions of dinosaurs that must have lived during the 160 million year period known as the Mesozoic era. What was it like then? At the beginning of the Mesozoic Era, called the Triassic period, when dinosaurs first evolved, low shrubbery-fern-like plants dominated the landscape. Next came the Jurassic period, when huge coniferous forests and groves of cycads supported the heyday of the plant-eating dinosaurs. Then came the Cretaceous period, when the western part of North America was covered with extensive rivers, deltas, swamps, and marshes. When large herds of grazing dinosaurs were hunted by a smaller number of meat-eaters. Flowering plants had just begun to appear. And the air was thick

with T. rex breath. Although no one claims that T. rex could kill with its breath, some believe the bacteria level was so high in its mouth that T. rex had only to deliver one septic bite, then wait until its prey was brought down by the ensuing infection. Not so far-fetched when you consider the Komodo dragon, the largest living lizard, which uses such a septic bite when hunting. [heavy breathing] In 1907, Barnum Brown found the third T. rex. With eight inch teeth in a four-foot-long skull, it was the most complete T. rex to date. And would remain the largest found for the next 60 years. The use of modern heavy equipment has greatly sped up excavation and transfer to the

lab. A big help when the block of stone containing a perfectly preserved hadrosaur tail can be two yards of solid rock. Even in two-legged dinosaurs, the tail served as a balancing mechanism to counterweight various body builds and head designs. From the smallest baby hadrosaur, less than a yard in length, to the 10-foot-long, meat-eating Albertosaurus. balance was crucial when several tons of dinosaur decided to run. Imagine a multi-ton ostrich and you begin to get an idea of how the swiftest of dinosaur predators might have moved. But how fast were they? Paleontologist can calculate the answers from fossilized footprints called "trace fossils." The race to clock T. rex's top speed remains the subject of great debate.

Opinions range from as slow as 15-miles-an-hour to as fast as 40- miles-an-hour. It's certainly safe to say that a man would be lucky to finish the race. Fortunately for humans, the only dinosaur bite we'll ever deal with is its overbite. The largest on record belongs to T. rex number four, found in 1966. The study of dentition, or the shape, size, and wear of teeth, tells us more about feeding habits than anything else, and dinosaurs have left us great dental records. The record for the most teeth belongs to Edmontosaurus, also known as the Tooth Fairy's nightmare. Over 1,000 acted like self- sharpening vegetable graters. The largest herbivores, such as Diplodocus and Brachiosaurus, had peg- shaped teeth, much like a horse, which they used like rakes to strip leaves and

needles off trees. Many of them didn't chew their food, they swallowed it whole. And what about the meat-eaters who fed on these herbivores? From the Albertosaurus to the crocodile-like Baryonyx. Most meat-eaters, or carnivores, had dagger-like teeth and many, such as T. rex, had teeth with serrations like those on a steak knife to help rip meat off the bone. [sounds of dinosaur killing and eating] [dinosaur roar]

[dinosaur roar and breathing] But T. rex's bark might have been worse than his bite. Were the biggest carnivores to walk the earth killers or just scavengers? The best evidence that they hunted live prey is in fossilized footprints of one large theropod stalking a sauropod herd. This kind of evidence also supports the theory that large herds of grazing dinosaurs were hunted by a smaller number of predators, making the Mesozoic seem not unlike the African savannah of today. [dramatic music] With sickle-like claws on its hind legs, Deinonychus, or "terrible claw,"

was the dinosaur equivalent of pack-hunting wild dogs or wolves. From a find in Montana, we know that the one-hundred-and-fifty-pound Deinonychus hunted down live prey. The scene was reconstructed using hard evidence from the site. A Deinonychus pack brought down a Tenontosaurus but not without paying a price. Before succumbing, the Tenontosaurus killed four of its attackers. Similar finds have revealed pack-hunting raptors at the sight of other kills. The carnivorous dinosaurs no longer hunt but are now hunted, themselves, by a human pack of fossil hounds. In 1981, three Canadian high school students found the next T. rex, Black Beauty, named after the color of its fossilized bone. Only after it was cleaned in the lab did anyone realize how complete this five-foot-long skull was.

But not all dinosaurs were is big as T. rex. Many of them were, in fact, quite small, as small as a bird. And they came in all shapes and sizes. With the heavyweight title going to Brachiosaurus, tipping the scales at 77 tones. That's heavier than two Boeing 737s. Although the largest dinosaurs have traditionally played the leading roles in popular entertainment, it's the smaller dinosaurs that have starred in the debate over dinosaur descendants. Compsognathus and Coelophysis have similar skeletons to Archaeopteryx, the first bird. This missing link supports the theory that modern birds are the nearest living relatives of small meat- eating dinosaurs and the nearest relatives of large dinosaurs like Baryonyx are crocodiles.

The ninth T. rex was found in 1987 and provided the first known tip of the tail vertebrae. All the bones of T-Rex had now been found except for those of its mysteriously shriveled forelimbs. The same area in North America that produced eight of the ten known T. rexes to date produced a find that would radically change our view of dinosaur family life. A massive bone bed was discovered, spread over several miles and estimated to contain the remains of a dinosaur herd ten thousand strong. Proof that dinosaur herds once roamed the American West like the buffalo of a more recent era. The most significant find was the nesting grounds. Much like present day sea birds which nest in colonies, these dinosaurs, called Maiasaura, also nested in groups. The eggs were laid in circular nests six-feet-across, containing twenty to twenty- five seven-inch eggs.

They belong to several Maiasaura, or "good-mother lizards," who shared nesting, feeding, and babysitting duties once the young were hatched. We know the hatchling stayed in the nest and were fed by their parents because the nest was filled with trampled shells. Sometimes dinosaur eggs provided food for others. Oviraptors, literally "egg thieves," were bird-like dinosaurs that liked their eggs raw. Like many modern-day birds and reptiles, hadrosaurs has had to guard their nests against predators. Dinosaurs probably also shared another trait with today's birds and reptiles. They used sound to communicate with their young. And some dinosaurs were louder than others. Edmontosaurus had an inflatable nasal sac which amplified its call, much like many animals living today. [animal calls]

Dinosaur headgear was also used for a less harmonious activity. Headbutting was probably the most popular way of resolving differences over territory or potential mates. This tradition is still alive and well in many animals today. In fact, it's now believed that Triceratops, with its three horns and massive frill, saw more action going head-to-head with other Triceratops than it did in the popular image of a one-on-one with T. rex. Another long-held belief was shattered when the tenth T. rex was excavated by John Horner in 1990. His fossil, 90 percent complete, was the first to produce a complete fore- limb. The notion that T. rex had three fingers, accepted since 1902, was

false. T. rex only had two. But in the serious game of paleontology, much larger mysteries still remain and opposing theories vie for the answers. Were dinosaurs cold-blooded like reptiles or warm-blooded like birds? It's the kind of question paleontologists love to argue long into the night. Those who contend dinosaurs were warm-blooded point to fossils found as far north as Alaska and Northern Canada. They say dinosaurs must have been warm-blooded because cold-blooded animals, at the mercy of external temperatures, couldn't have lived in such cold. [dramatic music] Warm-blooded theorists also contend that dinosaurs must have had the four-chambered

double-pump heart of today's mammals to supply them with enough blood pressure to pump blood up their long necks to their heads. The heart of a cold-blooded animal couldn't have pumped enough blood to their brains and they would have been constantly fainting. But the strongest evidence for dinosaurs being warm-blooded is that their bones are honeycombed with holes, Proof of a network of blood vessels as complex, if not more complex, than living mammals. Those who contend that dinosaurs were cold-blooded say all this evidence is full of holes. They claim dinosaurs living in the cold north were mobile enough to head south for the winter and they gleefully point to the crocodile which has a four-chambered heart yet is still cold-blooded. They also suggest that the dinosaur's large size would have allowed it to store a great amount of heat. Warm-blooded? Cold-blooded? Given the lack of evidence,

the real answer may never come to light. One thing paleontologists have few arguments about is how dinosaur muscle lay on the bone. They can read the bones by looking at the ridges of smooth patches and grooves, and determine how muscle, tendons, nerves, and blood vessels were arranged. However, laying skin over the muscle is more a matter of guesswork. From fossilized skin impressions we know that dinosaur skin was much like that of modern reptiles: scaley, tough, and waterproof, and probably came in the same variety of colors. To break up the outline of a body, some may have had stripes. Since blending in was important, polka dots were unlikely. But armor was very popular. The toughest armor belonged to Ankylo- saurs. And, yet, even armor couldn't protect the Ankylosaurs, or any of the dinosaurs, from extinction. The greatest mystery of the dinosaurs

is the what-done-it of their extinction. There are many theories. One holds that a huge increase in ultraviolet rays gave dinosaurs cataracts and they stumbled blindly into extinction. It was once believed they became so huge and lethargic, they died of boredom. One of the more widely held theories is supported by the fact that about the time the dinosaurs disappeared, a meteor five-to-10-miles-wide hit the Earth, throwing up a crater 93-miles-wide and surrounding the earth in a huge cloud of dust and steam which blocked out the sun for months, possibly years. The only problem with this theory is that fossil teeth have been found from dinosaurs that lived long after this cataclysmic event. Of one thing we are certain: after 160 million years of dominating the Earth the dinosaurs did die out.

But life on Earth continued to evolve until humans came along, to ponder these fossilized remains and indulge in their fantastic reality. Some would say, all over the world dinosaurs have made quite a comeback and there are more today than ever before. Although they are far from real, perhaps they are the children born of our fertile imaginations and the hard evidence of dinosaurs mere shadows in the stone. [musical fanfare] Certainly there are many more dinosaurs waiting to be discovered. Many new mysteries waiting to be pondered.

And if it's true that life imitates art, maybe someday we'll even bring them back to life. [end credits music] [OPB jingle] Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual financial support from viewers like you. To order a video cassette of this 'Eyewitness' episode call PBS Video at

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