Hot-Blooded Dinosaurs?

Dinosaurs are generally regarded as overgrown lizards--pea-brained, coldblooded creatures that spent most of their lives hulking sluggishly in the sun. This image is unfair, argues Adrian Des mond, 28, an English-born doctoral candidate at Harvard University. Desmond, who studied vertebrate paleontology at London University, has spent the past several years reviewing the latest research on the huge creatures that ruled the earth for 140 million years. In a new book titled The Hot-Blooded Dinosaurs (Dial Press; $12.95), he contends that some dinosaurs and their kin were warm-blooded, complex and far more intelligent than some of the species that succeeded them.

In the Cold. Desmond bases his argument on a comparison of dinosaurs and modern-day reptiles like the lizard. Cold-blooded animals, whose bodies are small by comparison with most mammals, control their body temperatures by moving into or out of the sun. If dinosaurs were coldblooded, maintains Desmond, they would not have been able to do this because of their size (a brontosaur, for example, weighed around 30 tons); a dinosaur whose body temperature dropped just one degree below the warmth necessary for it to be active would have to bask in the sun for at least several hours to bring it back to normal. Thus, says Desmond, Strithiom-imus, the "ostrich dinosaur," could not have hit the 50 m.p.h. speeds it was said to have attained if it had a physiology comparable with that of a modern-day lizard. The Tyrannosaurus could not have engaged in its earth-shaking battles with the rhinocerine Triceratops unless it had the high metabolic rate of a warm-blooded creature.

Desmond also supports an explanation of the dinosaurs' sudden disappearance that is compatible with the warmblooded theory: at the end of the Cretaceous era, about 70 million years ago, the earth's climate rapidly cooled. Cold-blooded reptiles, such as turtles and crocodiles, were able to find cozy nooks and survive the winters by hibernating; small, fur-covered mammals built warm nests. Dinosaurs could not. Too big to find protective caves or burrows in which to hibernate, they stayed out in the cold and died.

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