T. rex teeth suggest its body ran as warm as an elephant's
UCLA researchers analyzing isotopes in T. rex tooth enamel found the dinosaur's body temperature was around 36 degrees Celsius, similar to a modern elephant, supporting the idea it was warm-blooded.
A research team led by geochemists Randon J. Flores and Robert A. Eagle at the University of California, Los Angeles has estimated Tyrannosaurus rex's body temperature by studying its teeth. Their measurements point to roughly 36 degrees Celsius, close to the body temperature of modern Indian and African elephants.
The study examined three T. rex teeth from Montana's Hell Creek Formation, supplied by the Natural History Museum of Los Angeles County. Two teeth came from a young adult likely weighing over three tons, while a third partial tooth belonged to another individual. For comparison, the team also analyzed five teeth from crocodilians that lived alongside T. rex in the same rivers and floodplains.
A new measuring method
Earlier attempts to gauge dinosaur temperature using oxygen isotopes were unreliable because results were skewed by the water composition inside the animal's body. This time, researchers used clumped isotope thermometry, a technique that tracks how often rare carbon-13 and oxygen-18 atoms bond together within carbonate minerals in tooth enamel — a process governed purely by the temperature at which the mineral formed.
Before drawing conclusions, the team verified that 66 million years underground had not altered the chemistry of the teeth, using several checks including infrared spectroscopy, which confirmed the enamel's structure remained intact.
Warmer than its surroundings
The measurements showed T. rex ran noticeably warmer than the crocodilians, which averaged 30.9 degrees. Comparing this with climate models of the era and isotope data from freshwater mussels — indicating summer water temperatures around 26 degrees — the researchers concluded T. rex was consistently warmer than its environment.
The team also built a model suggesting that thanks to its ability to maintain a stable body temperature across a range of conditions, T. rex could have lived across nearly all of North America, from humid southern regions to colder northern areas including Alaska. The authors caution, however, that body temperature alone doesn't settle the debate over the dinosaur's exact metabolic strategy.
