Dragons & Dinosaurs

How do we know we are right when we imagine the past? Well, we really don't. We weren't there. When it comes to dinosaurs, scientists have only bones and fossils-and now computers-to help them understand how these ancient beasts might have looked.

Until very recently, people didn't know what the world was like before humans. They didn't understand that entire species could disappear from the earth, or go extinct. The last dinosaurs died 65 million years ago. The first modern people began to inhabit the earth millions of years later. So no human ever saw a living dinosaur. But our ancestors did find-and wonder about-dinosaur bones.

Prehistory Mystery

Ancient people had their own ways of explaining the strange bones they found. They thought the bones were the remains of giants, dragons, sea monsters, and other creatures you read about today in fairy tales and myths. Consider the legend of the griffin, a fantastic cross between a lion and an eagle once believed to live in the deserts of China. People all over the ancient world-Asia, the Middle East, and Greece and Rome-told stories of these griffins. Each culture imagined them differently, but most ancient art shows them with gigantic beaks, claws, wings, and catlike bodies.

Now take a look at the skull of a small dinosaur we call Protoceratops. Scientists have found many of these skulls in the Gobi Desert in Mongolia (a region of China), where Protoceratops lived about 80 million years ago. Protoceratops had a huge, birdlike beak designed to chop up the plants it ate and to defend itself. A large "frill" on its head and bony bumps on its cheeks (probably both a form of protective armor) give its skull a monstrous look. Ancient people who saw these skulls guessed that they were the remains of winged, lionlike birds that guarded gold in the desert mountains. They thought they were griffins.

The ancient people were not far from wrong. These were the bones of amazing creatures, though not human giants, nor dragons, nor griffins. In the 1800s, scientists began to recognize that ancient bones and fossils belonged to long-extinct animals, which no one, of course, had ever seen. The mystery deepened.

What did these animals really look like? The task of arranging the bones in the proper order and accurately imagining the flesh and muscle that covered them was quite a challenge.

The Terrible Lizards

Pretend for a moment that you have never seen a bicycle before. You have no idea what it does or how it is used. Now suppose you stumble upon a funny-looking triangular leather thing sticking out of the earth. Next to it lies a curved metal bar with plastic ends. Farther along, a piece of rubber. What could these things be? Are they parts of a single contraption? Are they related to anything you know about? How do they fit together? How many, and what, pieces are missing?

This gives you an idea of the questions scientists ask when they find dinosaur bones. Just over a hundred years ago, the first scientists to study them thought these bones belonged to gigantic, ferocious lizards that once roamed the earth. A brilliant English scientist named Richard Owen recognized that these creatures were different enough from modern reptiles to deserve their own name. He called them dinosaurs, from the Greek for "terrible lizard." Though Owen was correct to group them under one name, he didn't realize that some dinosaurs were small and harmless. And though dinosaurs belong to the reptile family, they are very different from lizards.

Iguanodon was among the first dinosaurs to be scientifically described. Its discoverer, Gideon Mantell, believed that the very large teeth and bones he found must have belonged to a huge iguanalike creature whose legs sprawled out to the side like those of a lizard. Mantell thought that the large pointed object his wife discovered was the creatures nose horn. Over the years, scientists changed their minds many times about the appearance of Iguanodon. Today we know that it had four straight legs, like a mammal, and could walk either on two hind legs or on all fours. That spiky object mistaken for a horn was really a long, sharp toenail.

The Case of the Deceptive Dinosaur

Today we know of more than 1,000 species of dinosaurs, and others are being discovered every year. Paleontologists, scientists who study bones and fossils to learn about the past, have a tough job keeping up with all the bones. When bones are first discovered, it is sometimes difficult to know what animal they belong to. Is it a new dinosaur or one we already know about? And when the bones of more than one creature are jumbled together, scientists must be careful to separate and identify y each animal.

Take the case of poor old Apatosaurus (whose name means "deceptive lizard"). Now there's a dinosaur with an identity crisis. This huge 30-ton creature was first discovered and named in 1877. Two years later, the same scientist examined another set of Apatosaurus bones and thought they belonged to a different type of dinosaur, which he named Brontosaurus (or "thunder lizard"). With its long graceful neck and whiplike tail, Brontosaurus became a familiar favorite among dinosaur lovers. But, in 1974, scientists decided that Brontosaurus was really Apatosaurus-that there was no Brontosaurus after all.

To make matters worse, Apatosaurus lost its head. Honestly. Because the original skeleton was found without a head, no one was sure what Apatosaurus's skull looked like. For nearly 100 years, models and drawings in museums all over the world showed it with no head, or the wrong head. Finally, the skull was located in a museum basement, and Apatosaurus could once again hold its head up proudly.

Or maybe not. Recent evidence indicates that Apatosaurus and other dinosaurs with long, elegant necks may not have been able to lift their heads far off the ground. For many years, experts believed that these vegetarian dinosaurs reached their necks into the treetops to dine, like giraffes. Recently, however, computer modeling has revealed that the positioning of their neck bones would have prevented them from raising their heads any higher than about 12 feet. While it may have been able to rear up on its hind legs to snag treetop treats, more often Apatosaurus probably reached its long neck across creeks or other obstacles as it grazed for food along the ground.

Listening to the Bones

Computers have become a valuable tool to help paleontologists picture dinosaurs better. Scientists can now even hear what dinosaurs might have sounded like. Consider Parasaurolophus, an oddlooking fellow. A large, bony crest extended from the top of its head back over its shoulders. Handsome, perhaps, but what did the crest do? Some scientists think it may have been a weapon or even a snorkel, but no evidence supports these ideas. How about a trombone? When a nearly complete Parasaurolophus skull was found in New Mexico, computer scientists and paleontologists joined forces to see if the head crest might actually have been a noisemaker. They took scans of the inside of the crest with special imaging equipment so that they wouldn't have to break it open. Then they used the scans to model a three-dimensional image of the crest. They found that it was filled with a complicated series of hollow tubes and chambers. When the computer created the sounds made by blowing air through the crest, the scientists heard an eerie, deep rumbling tone. Were the scientists hearing a sound not made on earth for 65 million years.

Who can know?

Snorkel? Weapon? Noisemaker? Parasaurolophuss curious crest has scientists guessing.

* To hear a dino roar, go to http://museums.state.nm .us/nmmnh/p3_staff_res_ sounds.html.

* To see computer images of dinos in motion, go to http://nationalgeographic .com/dinorama/sauro/html or http://palaeo.gly.bris.ac.uk /dinosaur/animation, html.

Copyright Carus Publishing Company Sep 2004
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