Technology and Science18 September, 20263 min read
Study Estimates Tyrannosaurus Rex Body Temperature at 36°C Using Tooth Enamel Chemistry
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UCLA scientists analyzed fossil tooth enamel to estimate T. rex temperature at 36°C. The study provides direct chemical evidence that Tyrannosaurus rex was warm-blooded.
Teeth as Thermometers
A new study used the chemistry of Tyrannosaurus rex tooth enamel to estimate the dinosaur’s body temperature at about 36° Celsius, roughly the body temperature of a modern elephant.
“This dental thermometer read about 36° Celsius—roughly the body temperature of a modern elephant.”
Ars Technica reports that a team led by Randon J. Flores and Robert A. Eagle, geochemists at the University of California, Los Angeles, measured the temperature by analyzing “clumped isotope thermometry,” a method Eagle introduced to dinosaur research over a decade ago.
The approach relies on how often rare heavy isotopes of carbon and oxygen bond together in carbonate minerals in tooth enamel, with the number of those clumped bonds recording the animal’s body temperature regardless of water composition.
El Món says the study, published in the journal Science Advances, used two fragments of teeth from Thomas, a nearly complete T. rex skeleton preserved at the Los Angeles County Museum of Natural History.
El Món also quotes Robert Eagle saying, “this is the most direct and least complicated constraint that has been established so far on the real body temperature of a T. rex.”
Warm-Blooded, Like Humans
Multiple outlets frame the result as evidence that T. rex was warm-blooded, with Smithsonian Magazine saying the fearsome predator ran at a toasty 97 degrees Fahrenheit, around the same temperature as modern-day humans. Smithsonian Magazine reports that the study was published September 16 in the journal Science Advances and that the team analyzed three fossilized dinosaur teeth from the Natural History Museum of Los Angeles County, including two from a T. rex named Thomas. CBC adds that Aradhna Tripati said, “You would not want to go to a T. rex and stick a thermometer in its mouth or in its armpit or in its butt,” emphasizing why chemistry in hard tissues like tooth enamel and eggshells was needed.
CBC reports the researchers estimated T. rex’s body temperature at between 33.8 C and 38.8 C, placing it “similar to that of large mammals such as elephants” and large and possibly flightless birds such as ostriches. In the same CBC coverage, Anthony Fiorillo said the paper “makes a solid and compelling case,” while François Therrien said the warm body temperature suggests T. rex could be active during the day, at night and in winter.
What the Number Changes
Beyond settling whether T. rex was warm-blooded, the study’s temperature estimate is used to connect physiology to behavior and geographic range, with Scientific American saying the enamel chemistry is “truly recording the temperature at which it formed.” Scientific American reports that researchers measured isotopes within T. rex tooth enamel found in modern-day Montana and found the dinosaur likely ran at around 36 degrees Celsius, similar to the internal body temperature of modern-day humans. Ars Technica explains that earlier attempts relied on oxygen isotopes in bones and teeth, but those ratios depend on water composition, which was something “nobody could pin down for an extinct creature,” motivating the clumped-isotope method.
“We found T. rex was 36°C (97°F), about the same as humans.”
New Scientist quotes Robert Eagle saying, “We found T. rex was 36°C (97°F), about the same as humans,” and adds that the reconstructed temperature was higher than ambient temperatures in prehistoric Montana. Scientific American says Eagle hopes to use the same technique to “suss out the body temperatures of avian dinosaurs and ancient mammalian ancestors next,” extending the stakes from one iconic predator to broader questions about how warm-bloodedness evolved.