A 66-Million-Year-Old Tooth Shows T. Rex Ran Almost as Warm as a Human Body

The most effective thermometer for Tyrannosaurus rex might have been in its mouth. A research revealed on 9/16/2026 in Science Advances used chemical signatures locked inside fossil tooth enamel to estimate how sizzling the predator ran, touchdown at about 97 levels Fahrenheit, almost a human physique temperature. “Nobody’s been in a position to make a temperature measurement like this earlier than,” UCLA geobiologist Robert A. Eagle mentioned, after the crew drilled tiny enamel samples, dissolved them in phosphoric acid, and browse the ensuing fuel in a mass spectrometer. The UCLA group says the tooth level to an animal that stayed hotter than its environment, strengthening the long-running case for warm-blooded tyrannosaurs.

Unearthing a dinosaur’s temperature

One of the vital surprisingly “trendy” numbers in science landed this fall: 97 levels Fahrenheit. A research revealed on September 16, 2026, in Science Advances used chemical signatures locked inside fossil tooth to place a direct estimate on how heat Tyrannosaurus rex probably ran in life, roughly matching a human physique.

For many years, researchers have argued over whether or not massive dinosaurs have been warm-blooded or extra reptile-like. This work is notable as a result of it strikes past inference and into measurement, the sort of step-change you normally see when new lab strategies mature and at last get utilized to an outdated, cussed query.

What tooth enamel can retailer for 66 million years

The research was led by UCLA geochemists Randon J. Flores and Robert A. Eagle, who analyzed three T. rex tooth to estimate physique temperature. Two of these tooth got here from a skeleton nicknamed “Thomas,” held on the Pure Historical past Museum of Los Angeles County and preserved to about 70% completeness.

The core trick: tooth enamel preserves uncommon “clumped” bonds between carbon and oxygen isotopes, and the abundance of these clumps rises in cooler temperatures and falls in hotter ones. Enamel’s massive, sturdy crystals resist chemical change over tens of millions of years higher than bone does, making it an unusually dependable archive for this type of forensic chemistry.

The lab work behind the headline quantity

To learn that temperature sign, Flores and Eagle used a dental drill to gather tiny enamel samples, dissolved the powder in phosphoric acid, then measured the carbon dioxide fuel with a mass spectrometer. Eagle summed up the second plainly: “Nobody’s been in a position to make a temperature measurement like this earlier than.”

The outcome landed at about 36°C, or 97°F. Eagle put it much more immediately: “We discovered T. rex was 36°C (97°F), about the identical as people.” The authors famous they might not utterly rule out seasonal bias, although samples from completely different components of the Thomas tooth produced statistically indistinguishable temperatures.

Heat-blooded, however not bird-hot

That 97°F estimate sits above trendy cold-blooded reptiles, which generally run round 82 to 86°F, however under birds, which regularly clock 104 to 109°F though they’re evolutionary descendants of dinosaurs. The center floor issues, as a result of it suggests tyrannosaurs generated substantial inside warmth with out essentially working like immediately’s high-octane birds.

UCLA professor and co-author Aradhna Tripati linked the physiology to geography: “What the tooth inform us is that T. rex was hotter than the surroundings round it,” and “A warm-blooded T. rex is a T. rex that may go virtually anyplace on the continent, together with the Arctic.” The research provides to cold-tolerance proof like a T. rex footprint present in Alaska in 2022.