Rare Fossil Shows Dinosaurs As Fast,...( iscovered just a few years ago of a bab...)

"Besides an intact skeleton, this fossil shows remnants of liver, large intestine, windpipe and even muscles," Jones said. "The baby dinosaur probably died in a shallow, still, saltwater marsh that preserved its structure incredibly well. It's like a Rosetta stone for paleontology, and shows us more about dinosaur biology than we ever knew before."

Of particular importance, the researchers said, is the clear presence of a complete separation of the body cavity into two parts, one containing the lungs and heart, and the other holding the liver and guts.

This sort of body cavity partitioning is only seen in living animals that use an active diaphragm to help ventilate their lungs, such as mammals and crocodilians. Like crocodiles and alligators, the liver of these carnivorous dinosaurs was pulled back by large muscles that attached to a distinctive bony element of the pelvis. These muscles pulled the liver back, causing it to act like a piston.

This "hepatic piston" mechanism probably enhanced the capacity for high levels of oxygen exchange - and the fast-paced activity associated with it - that could have rivaled that of some mammals.

"This type of physiology would provide some metabolic advantages unlike that of any animal still alive today," Jones said. "But for various reasons it only works well in a warm, equitable climate, which most of the world had during the age of dinosaurs. When the climate turned colder or more seasonal variation developed, what had once been the advantage of the dinosaurs became their problem."

The lungs and other structures found in this dinosaur fossil bears little similarity to that of modern birds, the researchers said, and they contin
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Contact: Terry Jones
jonest@bcc.orst.edu
541-737-6120
Oregon State University
21-Jan-1999