January 22, 1999
Web posted at: 7:28 p.m. EST (0028 GMT)

CORVALLIS, Oregon (CNN) - A study of an Italian dinosaur fossil suggests meat-eating dinosaurs called therapods had a specialized lung structure that allowed them to engage in vigorous, aggressive activity when necessary.

Scientists have known very little about the internal anatomy of dinosaurs until recently, because their soft, internal organs and tissues were rarely preserved and almost entirely absent in the fossil record.

But by using ultraviolet light, scientists examined an extraordinarily well preserved 110 million-year-old fossil of a baby therapod found in Italy. They were able to visualize the remains of many internal organs. The research was conducted by Nicholas Geist and John Ruben at Oregon State University and published in the journal Science this week.

Many scientists believe that dinosaurs were coldblooded, which means they had slow metabolic rates while at rest or in the cold -- their bodies did not expend energy to keep themselves at a consistently warm temperature.

But, if they had to move fast -- to fight, or to pursue prey -- their specialized lung structure could pump oxygen quickly into the lungs and bloodstream.

"The therapod dinosaurs were fast, dangerous animals," said Geist. "They could conserve energy much of the time and then go like hell whenever they wanted to."

The scientists identified the liver, large intestine, windpipe and some muscles of a dinosaur species known as Scipionyx. Most significantly, they found the dinosaur had a diaphragm that divided the body cavity into two parts -- the top part containing the heart and lungs, the bottom containing the liver and entrails.

The finding is bad news for scientists who theorize dinosaurs and birds could be closely related. Birds have an entirely different lung structure, and the differences between the two pulmonary systems do not suggest a close relationship.

"This fossil is helping confirm that the dinosaurs were indeed, by definition, coldblooded, and that in all likelihood birds are not the descendants of any known group of dinosaurs," Geist said.

Therapods like Scipionyx ate meat and walked on their hind legs. They had big heads with large mouths and teeth, long tails and small forearms. Geist, a paleobiologist, said the specimen he used may be the best-preserved dinosaur fossil ever found.

The research offers insight into how the dinosaurs were able to dominate their world for 150 million years. Geist called the fossil a potential "Rosetta stone" for dinosaurs, a reference to the discovery that allowed archaeologists to decipher ancient Egyptian writings.