Fossile Suggests Dinosaurs Had Super-Powerful Lungs And Were Deadly Hunters

Fossile Suggests Dinosaurs Had Super-Powerful Lungs And Were Deadly Hunters

By PAUL RECER

WASHINGTON (January 21, 1999 10:45 p.m. EST http://www.nandotimes.com) - The best-preserved dinosaur fossil ever discovered suggests some of the extinct animals had the super-powerful lungs needed to be fast and deadly hunters.

A 110 million-year-old fossil of a baby dinosaur called Scipionyx is so well-preserved that researchers believe it bears the image of some of the animal's internal organs, said Nicholas Geist, a paleobiologist at Oregon State University.

"The extraordinary condition of the fossils allows us to hang some meat on the bones of these animals," said Geist, the senior author of a study appearing Friday in the journal Science.

"What you usually get in fossils is just bones, but in this one there are remnants of liver, large intestine, windpipe and muscle," he said. "It is like a Rosetta stone for dinosaurs."

Scipionyx was a theropod, a type of meat-eating dinosaur that walked on its hind legs, had a long tail, small forearms and a big head with a large mouth and teeth.

The soft tissue impressions show that the Scipionyx had a two-partition abdominal cavity, with the lungs and heart in one section and the liver and guts in the other. The liver was connected by muscle to a pelvic bone, Geist said, suggesting the animal had a breathing system called a hepatic piston.

In such a system, muscles pull against the liver, causing the breathing cavity to expand slightly. That forces air into the lungs at a high rate.

"This is necessary for sustained activity," said Geist. "These theropods were exceedingly fast and dangerous animals. They were not slow and sluggish like many modern reptiles."

Mammals have a diaphragm muscle that causes the lung cavity to expand and draw in air. The ability to rapidly ventilate the lungs is essential for moving swiftly for long periods.

Dinosaurs' lung capacity may be one reason they dominated mammals for about 150 million years, said Geist. Mammals during this period were small and no match for the meat-eating dinosaur.

"These dinosaurs were fierce animals that could run prey down over extended distances," Geist said. "This was like a turbocharged lizard. The mammals couldn't get a foothold and just tried to stay out of the way."

The hepatic piston works best in a warm, mild climate such as the Earth enjoyed during most of the dinosaur era. When the climate chilled, the dinosaurs were in trouble, Geist said.

"These animals may have been so specialized for the warm climate, that even a minor change over an extended period may have helped do them in," he said.

But not all experts agree that the Scipionyx fossil gives such precise evidence of a hepatic pump breathing system, said Paul Soreno, a dinosaur expert at the University of Chicago.

"For many in the field, that interpretation is controversial," said Soreno.

The Scipionyx fossil, the only dinosaur ever found in Italy, is small enough to hold in two hands and the animal may have been only days old when it died. Geist said it perished in a saltwater marsh that preserved its body structure.

No fossil for an adult Scipionyx has been found and Geist said the animal species probably grew to only about the size of a large dog.