Gainesville, Fla. -- If you think dinosaurs are hot today, just think back to about 110 million years ago when they really ran hot and heavy.

One of the larger animals, a behemoth called Sauroposeidon proteles, weighed close to 120,000 pounds as an adult. Now, a new study led by the University of Florida suggests it may have had a body temperature close to 48 degrees Celsius.

That is a 118-degree Fahrenheit normal temperature, about as hot as most living creatures can get before the proteins in their bodies actually begin to break down.

In fact, the size of the largest dinosaurs may ultimately have been limited by their body temperatures, according to a team of scientists from the UF Genetics Institute, the National Center for Ecological Analysis and Synthesis in Santa Barbara and the University of New Mexico writing this week in the online journal PLoS Biology.

"One of the first things to strike me about our results was that larger dinosaurs, for their size, were much more active than contemporary reptiles," said Andrew Allen, Ph.D., a researcher with the NCEAS. "If these animals functioned at temperatures of 35 or 40 degrees centigrade, it suggests that they operated at a rate more like today's mammals and birds. While the largest dinosaurs may not have been running around as fast as in 'Jurassic Park,' they certainly were very active given their extreme size."

Tyrannosaurus rex, one of the more familiar dinosaurs considered by the researchers, probably had a cruising temperature of about 33 degrees Celsius, which is just over 91 degrees Fahrenheit, according to lead researcher James Gillooly, Ph.D., an assistant professor in UF's department of zoology. Humans have a normal temperature around 98.6 degrees Fahrenheit and redline at about 108 degrees.

Researchers determined dinosaur temperatures -- long a subject of debate in biology -- by combining their understanding of relationships among body size, t
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Contact: John Pastor
jpastor@vpha.health.ufl.edu
352-273-5810
University of Florida
11-Jul-2006