It’s not every day you get to “take the temperature” of a creature that’s been extinct for 66 million years. But that’s exactly what a team of researchers from UCLA and the Natural History Museum of Los Angeles County have managed to do. Their work, published September 2026 in Science Advances, used a cutting-edge chemical technique to measure the body temperature of the world’s most iconic dinosaur, the Tyrannosaurus rex.
Cracking Prehistoric Physiology
Previous theories suggested that T. rex was probably warm-blooded, but scientists had no way to pin down its exact body temperature—until now. “We can’t just use a thermometer to do that,” joked Jasmina Wiemann, a Johns Hopkins paleobiologist not involved in the research. So the team turned to chemistry. By analyzing how atoms, particularly isotopes, bond together in the enamel of fossilized T. rex teeth, researchers could reverse-engineer the dinosaur’s core temperature. Heavier isotope pairs bond differently depending on temperature, leaving a chemical fingerprint scientists can read millions of years later.
Three teeth from “Thomas,” the resident T. rex at LA’s Natural History Museum, provided the evidence. The verdict? T. rex had an average body temperature of about 97.3 degrees Fahrenheit (plus or minus 4.5 degrees), or 36 degrees Celsius. That’s about as warm as a human—or an elephant. For comparison, ancient crocodiles from the same era clocked in at a much chillier 88°F.
Clues to a Dinosaur’s Lifestyle
“This gives us a direct window into dinosaur physiology that we’ve never had before,” said Robert Eagle, a geobiologist at UCLA and co-author of the study. The result confirms T. rex was warm-blooded, more like modern birds than cold-blooded reptiles. Such a high body temperature suggests T. rex could sustain activity even in colder climates, possibly explaining why their fossils are found all across North America—even in places that would have been frosty during the Cretaceous.
And there’s more: the same study offers a new tool to probe the biology of other extinct species. “There’s lots of interesting, charismatic species that could be explored using this,” Eagle added. With this method, questions about how dinosaurs survived harsh winters or roamed vast territories might finally get some concrete answers.
