DINOSAUR BIOLOGY

Most aspects of dinosaur biology cannot be observed directly but must be reconstructed by a variety of often speculative approaches. Overall body form can be established if good skeletal material of a dinosaur species is available. From a skeletal reconstruction, interpretations of the animal's soft parts, and inferences about how the creature's sk eleton functioned as a living machine, can be made. inferences about d inosaur habitat preferences and sociality are made from observations o f the preservational contexts of skeletons, nesting sites, and trackwa ys. Some aspects of dinosaur biology are interpreted on the basis of r elationships between body size and physiological and ecological parame ters in living animals, but this involves much uncertainty. Primary ti ssues of dinosaur bone suggest that dinosaurs had rapid growth rates, but calibrating dinosaur growth rates in terms of body mass gained per unit time is difficult. it is uncertain whether dinosaurs needed meta bolic rates comparable to those of living birds and mammals in order t o grow quickly enough to form the primary bone tissues commonly found in dinosaur skeletons. No evidence convincingly shows that dinosaurs w ere endotherms, and some evidence suggests that they were not. Dinosau rs routinely achieved considerably larger body sizes than do terrestri al mammals, and they maintained viable populations in smaller geograph ic areas than is possible for elephant-sized mammals. This suggests th at dinosaurian food requirements were proportionately less than those of birds and mammals, thus permitting large population densities.