How Do You Take a T. Rex's Temperature? Try the Teeth

To quote the UCLA press release about its researchers’ recent dino-discovery, “T. rex was a hottie!”

That doesn't mean paleontologists found evidence that Tyrannosaurus rex was handsome. Rather, they calculated the actual body temperature of the average T. rex.

“No one’s been able to make a temperature measurement like this before,” study co-author Robert Eagle said in the news release. “We found T. rex was 36 Celsius (97 Fahrenheit), about the same as humans." Eagle is a geobiologist. He explained that a T. rex was warmer than modern reptiles. It was probably cooler than today's birds, though.

Scientists have long suspected that T. rex and other dinosaurs were warm-blooded. Yet figuring out exactly how hot dinosaurs ran has been tricky. Eagle’s team used an innovative process. They examined the chemical building blocks of a T. rex's teeth. At lower body temps, certain isotopes of carbon and oxygen bind together. The cooler an animal’s body, the more of those isotopes there will be. The researchers drilled into several T. rex teeth. They analyzed their cores. Eagle's team found a number of isotopes consistent with that human-like 97 degrees.

Knowing how warm a T. rex’s body could be is “spectacular” on its own, scientists say. But there’s much more it can tell us, study co-author Aradhna Tripati explained.

“(Temperature) drives behavior, range, energy budget and how a species responds to a changing climate …,” Tripati said. “The teeth tell us T. rex was warmer than the environment around it." That means T. rex could have lived almost anywhere in North America, Tripati added.

Reflect: What's a small clue, like a tooth or a fingerprint, that you think could tell a surprising story about someone's whole life?

Photo of T. Rex mouth from Reuters.