NEW INSIGHTS IN DINOSAUR METABOLISM.

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A study by scientists at Oregon State University, Corvallis, of what they say is the world's most perfectly preserved fossil of a theropod, a meat-eating dinosaur, provides an unprecedented view of the biology of these ancient reptiles and new clues to their lifestyle. It offers insights into dinosaur metabolism, the warm-blooded vs. cold-blooded contorversy, the question of whether or not they might have been the ancestors of birds, and the biology that first helped them dominate the world and eventually may have led to their extinction.

"This fossil is helping confirm that the dinosaurs were indeed, by definition, cold-blooded, and that in all likelihood birds are not the descendants of any known group of dinosaurs," notes paleobiologist Nicholas Geist. "But the extraordinary condition of the fossil allows us to hang some meat on the bones of these animals and bring them back to life a little bit. It's almost like a dinosaur dissection."

What that analysis reveals is an animal that had the best of both worlds. Like other cold-blooded animals, these theropods had low metabolic rates while at rest, which is an excellent strategy for conserving energy. Meanwhile, enhanced lung ventilation capacity gave them the potential for the type of aggressive, extended activity typical of birds and mammals. "These theropod dinosaurs were fast, dangerous animals, certainly not slow or sluggish. They could conserve energy much of the time and then go like hell whenever they wanted to. That might go a long way towards explaining why they were able to dominate mammals for 150,000,000 years."

Geist and colleague Terry Jones made these observations after studying a fossil in Salerno, Italy, of a baby Scipionyx, a meat-eater that lived about 110,000,000 years ago and bore some similarity to a velociraptor. "Besides an intact skeleton, this fossil shows remnants of liver, large intestine, windpipe, and even muscles," Jones indicates. "The baby dinesaur probably died in a...