New Delhi, Sept. 18 -- Researchers once thought that dinosaurs were sluggish, cold-blooded creatures. Later findings challenged that, suggesting that older dinosaurs were warm-blooded and could control their body temperature.

Most scientists agree that Tyrannosaurus rex was warm-blooded, but pinning down the exact core temperature of an extinct creature is difficult.

"We can't just use a thermometer to do that," said Jasmina Wiemann, a paleobiologist at Johns Hopkins University who had no role in the latest work.

Scientists tried other methods like studying how T. rex grew or searching for clues in its bones, but a firm number eluded them.

In a new study, researchers hunted for chemical clues in the fearsome predator's teeth. It turns...