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Washington D.C. -- A computerized tomography (CT) scan of the chest cavity of a new dinosaur fossil reveals a heart more closely resembling a bird or mammal organ, rather than a modern reptile's. This discovery, which suggests that the dinosaur was warm-blooded, with a relatively high metabolism, is reported in the 21 April issue of Science.

When Michael Hammer, professional fossil collector and co-author of the Science paper, discovered the remains of a dinosaur in South Dakota, he guessed from the unusually well-preserved ribs that its chest cavity might hold some internal organs.

Although researchers don't fully understand how this happens, animals' soft tissues can sometimes become fossilized in oxygen-poor environments, such as the sediment beneath a streambed.

Instead of paring away the bones from their surroundings, Hammer carefully cleaned the surface of the skeleton. Before sending the specimen to its new owners at the North Carolina State Museum of Natural Sciences, physician Andrew Kuzmitz had its chest region CT scanned. A team from the Museum and from North Carolina State University produced three-dimensional images from the CT data and analyzed the results.

The images revealed two neighboring cavities and a single tubular structure positioned like an aorta. The cavities are probably the heart's lower chambers, the ventricles. The walls of the upper chambers, the atria, are usually very thin and probably collapsed when the dinosaur died. Birds and mammals also have four-chambered hearts with a single aorta.

Dinosaurs have traditionally been considered to be more clos
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Contact: Heather Singmaster
hsingmas@aaas.org
202-326-6414
American Association for the Advancement of Science
20-Apr-2000