NEW YORK (AP) — Using fossilized teeth, scientists have finally taken the T. rex's temperature — and it wasn't too different from our own.

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 out that atoms within the enamel clump together in different patterns based on an animal's body temperature.

“We figured out how warm the most famous animal of all, a T. rex, was,” said co-author Aradhna Tripati, a geochemist at the University of California, Los Angeles.

Readings from three teeth revealed an average body temperature of about 97 degrees Fahrenheit (36 degrees Celsius). That's similar to modern elephants and not too far from the average body temperature of humans, which ranges from 97 to 99 degrees Fahrenheit (36 to 37 degrees Celsius).

The findings were published Wednesday in the journal Science Advances.

“I almost would have expected a higher body temperature,” Wiemann said. Based on her prior work, she thought the predator could have run a few degrees hotter — similar to modern birds, dinosaurs' warm-blooded descendants.

Knowing how hot or cold the T. rex was can help scientists piece together how the dinosaur might have lived.

At 97 degrees (36 degrees Celsius), T. rex could have lived across most of prehistoric North America, Tripati said, maintaining a stable internal thermometer across both cooler and hotter regions. The findings could also shed light on the kinds of prey the dinosaur had to hunt in order to keep its energy up.

Scientists say it'll be important to test these methods on other dinosaurs to see how warm or cold they ran. It's possible T. rex's temperature could have been one of the keys to its dominance as one of the dinosaur age's top predators.

“There's lots of interesting, charismatic species that could be explored using this,” said study co-author Robert Eagle, a geobiologist at UCLA.

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