Scientists in California say they have for the first time devised a way to accurately take the body temperatures of dinosaurs — by examining the creatures’ teeth.
Chemical analysis of the Jurassic period fossil teeth from two sauropods — long-tailed, long-necked dinosaurs that rank among the largest land animals ever to roam the Earth — showed they were about as warm as most modern mammals.
However, they also were cooler than some experts had predicted for animals of such gigantic size.
The findings from a team led by researchers at the California Institute of Technology were published on Thursday in an online edition of the journal Science.
“This is like being able to stick a thermometer in an animal that has been extinct for 150 million years,” said Robert Eagle, an evolutionary biologist and post-doctoral scholar at Caltech who was lead author of the report.
The study supports a growing body of research suggesting dinosaurs were more active and energetic than scientists originally believed.
However, it leaves unanswered the key question of whether dinosaurs were cold-blooded, relying on their environments for heat, or warm-blooded, with self-regulated metabolism like modern mammals and their evolutionary descendants, birds.
Eagle said that determination would have to come with further analysis of a much greater range of dinosaur species.
The two dinosaurs initially selected for study — Brachiosaurus brancai and Camarasaurus — were close cousins of the massive plant-eating dinosaur known as brontosaurus.
The temperature of Brachiosaurus was measured at 38.2°C. Camarasaurus registered a temperature of 35.7°C. Researchers say those figures are accurate to within 2°C.
While equivalent to the temperature of most modern mammals, that range is warmer than modern and extinct crocodiles and alligators but cooler than birds.
Still, because of their sheer enormous size, sauropod dinosaurs would be expected to retain their body heat more efficiently than smaller warm-blooded animals, like humans, even if dinosaurs themselves were cold-blooded, Eagle said.
To explain this, researchers suggested the dinosaurs may have had some physiological or behavioral adaptation that allowed them to avoid getting too hot. One possibility is they dissipated excess heat through their long necks and tails.
In any case, scientists will learn more as they apply their new technique to other species, such as meat-eating predators like Tyrannosaurus rex or velociraptors, which were smaller and probably faster on their feet, Eagle said.
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