Eddy Jorczyk, age 11, of Milford, Connecticut, for his question:
How can they tell dinosaurs were plant eaters?
Dinosaur fossils were found long before the discovery of radioactive dating. They were unearthed in fragments an immense tooth, a giant thigh bone, a partial skeleton twisted out of shape by the pressure of massive rocks. For a long time nobody knew what a complete dinosaur looked like, or that they came in a vast assortment of shapes and sizes. Most people estimated the age of the earth to be but a few thousand years. Certainly nobody imagined that the owners of these strange fossils had populated the world through 160 million years.
The story of the dinosaurs was pieced together just a few generations ago. The first theorists were sure that these outlandish fossils belonged to creatures wiped out by Noah's flood. As more evidence was unearthed, one theory followed another. There were headlines, heated disputes and frantic scrambles to gain possession of every newly discovered fossil.
Nowadays, the discovery of a previously unknown dinosaur tooth is somewhat tame. A modern paleontologist can tell almost at a glance whether the previous owner fed on plants or meat. Chances are, he can estimate the size of the dinasaur and form a fairly accurate picture of his shape. He can guess whether such an animal lived in a swamp or on the dry land. Finally he uses a modern technique of radioactive dating to pinpoint just when his newly discovered dinosaur species lived.
To a paleontologist, the teeth of extinct animals possibly yield more information than any other type of fossil. After all, food is a vital item and sizable animals need built in tools to eat it. The carnivores (meat eaters) require toothy blades or sabre sharp beaks to tear their food into swallowable bites. The herbivores (plant¬eaters) have teeth with wide or domed crowns for chewing and chomping. The strength and quality of these teeth also tell whether their owners dined on tender foliage or tough vegetation.
The fossilized record of life on earth suggests that the ancestors of the dinosaurs were carnivores. Most likely they dined on amphibians, fishy food found in shallow waters and a few land insects. These primitive reptiles branched out and during the Jurassic Period of 180 million years ago an amazing array of their descendants dominated life on earth. Carnivorous dinosaurs with dagger sharp teeth thrived in the seas. Monstrous plant eaters lived in the swamplands, chewing tender waterweeds. On the dry land, a ferocious assortment of toothy meat eaters preyed on populations of plant eaters. The skeletons reveal that the carnivores were swift runners, equipped with taloned claws and rows of sharp pointed teeth. The slow moving herbivores defended themselves with massive bulk and outlandish armor and most likely reserved their flat topped teeth for chewing.
The dinosaurs departed some 60 million years ago but the pattern of meat and plant eaters still prevails. Our agile cats and dogs have dagger like teeth for tearing their meaty food. The rabbits and elephants have chewers and chompers to cope with vegetation. However, our bears and a number of other modern animals have both tearing and chewing teeth. They dine on a mixed diet of meat and vegetables, as we do.