Source: Reuters January 21, 1999

Fossil Shows Dinosaurs Were ``Turbocharged''

By Maggie Fox
Health and Science Correspondent

WASHINGTON - Meat-eating dinosaurs may have been technically reptilian, but they could run fast enough and long enough to chase down any prey they wanted, researchers said on Thursday.

Studies on the fossilized remains of a baby dinosaur found in Italy show it probably was cold-blooded like a reptile, but had the metabolic capacity of a modern mammal or bird.

``These theropod (meat-eating) dinosaurs were fast, dangerous animals, certainly not slow or sluggish,'' Nicholas Geist of Oregon State University, who worked on the study, said in a statement.

``They could conserve energy much of the time and then go like hell when they wanted to. That might go a long way toward explaining why they were able to dominate mammals for 150 million years.''

The researchers, working with a team at the Museo Civico di Storia Naturale in Milan, reported their findings in the journal Science.

A variety of studies are beginning to show that dinosaurs, at least the meat-eaters, were not the pondering, slow-witted creatures that people thought they were.

``If you could go back in time and saw one of them, that's probably the last thing you'd ever see,'' Geist said.

John Ruben, who also worked on the study, noted that reptiles such as crocodiles can move quickly in short bursts.

``They can sprint,'' he said in a telephone interview. ``The difference is that warm-blooded animals (such as birds and mammals) can maintain this for a lot longer. They have a lot more stamina. And that is what we are saying the theropod dinosaurs had.''

So they would be as quick and ruthless as a crocodile, with the stamina of a modern-day carnivore such as a lion.

``What you have is a turbocharged reptile,'' Geist said.

The researchers developed their theory after looking at very well-preserved remains inside the chest of a baby Scipionyx, a dog-sized predator similar to the velociraptors made famous in recent dinosaur fiction films such as ``Jurassic Park.''

``In that animal, under visible light, you can see distinct visceral organs like the intestines, the liver,'' Ruben said.

``But under ultraviolet light, the thing just literally started to glow. The intestines were much more visible, the liver became more visible, the muscles as they were preserved were more visible.''

The layout was like that of a creature that breathes with a diaphragm, like humans and other mammals do. That implies a breathing capacity much greater than that seen in most living reptiles.

If dinosaurs were cold-blooded, that could explain why they died out 65 million years ago, Ruben said.

``If these things are ectotherms or cold-blooded, they depend on the environment for their body temperature,'' he said. ``They are not maintaining body temperature because of a high metabolic rate like we do.''

That would be fine in the relatively warm climate of the Cretaceous and preceding periods. But the climate changed, going through much cooler periods and even ice ages.

Even a little cooling could have been enough to wipe out the dinosaurs, even before an asteroid hit and kicked up dust, as many scientists now think happened 65 million years ago, Ruben believes.

``Dinosaurs were beginning to lose diversity and disappear a good six to eight million years before the asteroid hit,'' Ruben said.

``They were on the way downhill for a long time. I would suggest that one reason might be that these were very highly specialised cold-blooded animals that could not survive easily in an environment that was becoming seasonally cooler.''