One of the hottest debates among dinosaur experts is whether the ancient reptiles were warm-blooded or cold-blooded.
Now a new study has found that the answer may have varied with the size of the dinosaur.
What's more, the beasts' body temperatures may have changed by as much as 36°F (20°C) as they grew up.
The finding, published online this week in the journal PLoS Biology, is based on a simple equation that applies to many modern animals.
That equation links young animals' growth rates to two factors: body size and body temperature.
"We found that that relatively simple model describes a lot of the variation in growth rates," said James Gillooly, a researcher at the University of Florida in Gainesville, who led the study.
Hot Math
Gillooly's brainstorm was to mathematically rearrange the equation to predict an animal's body temperature given the creature's size and growth rate.
Paleontologists have long been estimating dinosaurs' sizes from their fossils.
And growth rings in dino bones provide means of estimating their growth rates at various stages in their lives. (Related news: "One Size Didn't Fit All for Early Dinosaur, Study Says" [December 2005].)
Using this data, Gillooly's team calculated the body temperatures of eight species of dinosaurs, ranging from 25 pounds (12 kilograms) to 14 tons (13,000 kilograms).
The researchers also tested their model by doing a similar analysis for modern crocodiles ranging in size from 70 pounds (32 kilograms) to slightly larger than a ton (907 kilograms).
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