Our Changing View of Dinosaurs
One thing to keep in mind as your students search for information on dinosaurs is how significantly our understanding of dinosaur physiology and lifestyles has changed in the last 30 years. Forget dinosaurs as big, dumb, slow, lizard-like monsters. The current view is much more dynamic (and still controversial!).

Fossil evidence suggests that dinosaurs stood upright and could move rapidly. If so, such high levels of activity suggest warm-bloodedness. Other fossil evidence is consistent with a warm-bloodedness. However, arguments can still be made for their cold-bloodedness. For example, the large plant eater Stegosaurus (the one with the plates on the back and the spikes on the tail) might have used its plates to absorb the morning sun to warm its body. Fossil plates show grooves that apparently held blood vessels that enabled the dinosaur to warm (or cool) the blood by these "heat exchangers." You might want to pose the problem of body temperature regulation for large animals to students and ask them what differences exist between a warm- and a cold-blooded animal.

If dinosaurs moved quickly, then the tails of creatures like Tyrannosaurus rex might have acted as a counterbalance. The head would have been held low, almost the way a dog sniffs the ground, and the tail would have been stretched out to balance the large head

Some insight into dinosaur behavior has also been derived from studies of fossils. For example, a recent discovery in the Gobi Desert's Ukhaa Tolgod Valley in Mongolia suggests that at least one species of meat-eating dinosaur may have been nesters who cared for their young as birds do today. An Oviraptor was found on a nest of eggs in an association that indicates that the dinosaur died while protecting its brood. Ironically, the discovery also tells us how we mistook earlier Oviraptor finds. Oviraptor means "egg stealer," so named because although earlier finds associated the dinosaur with eggs, the limited evidence suggested to paleontologists that the dinosaur was eating rather than protecting the eggs.

Fossil evidence suggests that some plant eaters also cared for their young. This parenting is an important indicator that ties dinosaurs more closely to birds.

Another possible lifestyle was pack hunting. Even a large predator like Tyrannosaurus rex would have great difficulty bringing down a Triceratops, a scene often shown in popular books and movies. The adult three-horned, thirty-foot-long Triceratops weighed so much (4 or 5 tons) that a Tyrannosaurus might have simply lost its teeth if it bit into a running Triceratops. Pack hunting might have made an attack safer. Two or three T-rexes would have had an easier time than a single T-rex cornering and killing a Triceratops. The movie Jurassic Park shows Velociraptors hunting as a pack. If, as seems evident, nesting characterized some dinosaurs, then other social behavior, like pack hunting, is also probable.

On the other hand, some paleontologists suggest that Tyrannosaurus rex was not a ferocious hunter after all, but simply a scavenger like a modern day crow. If so, T-rexes would have usually eaten carrion, and only rarely hunted live prey.

Although we have learned much about dinosaurs in recent decades, we must keep in mind that much is still uncertain, and that there is much more to learn. The search for new fossils and the challenge of interpreting them continues!