A new study measuring the body temperature of Tyrannosaurus rex through dental analysis indicates the predator maintained a temperature near 36 degrees Celsius, comparable to modern elephants.

Researchers Randon J. Flores and Robert A. Eagle from the University of California, Los Angeles, applied clumped isotope thermometry to three T. rex teeth fossils from Montana's Hell Creek Formation. This method analyzes carbon-13 and oxygen-18 bonding patterns in tooth enamel carbonate minerals, which directly reflect the temperature at which the mineral formed, independent of surrounding water composition.

The technique overcame previous limitations of oxygen isotope analysis, which required assumptions about ancient hydration levels. By focusing on enamel's resistance to chemical alteration and verifying through infrared spectroscopy and isotopic consistency checks, the team confirmed the fossils' integrity over 66 million years.

Body temperatures averaged 36.3 degrees Celsius with a margin of error of 2.5, aligning closely with African and Asian elephants. For comparison, contemporaneous crocodilians from the same ecosystem registered temperatures around 30.9 degrees Celsius, reflecting their behavioral thermoregulation through aquatic and basking cycles.

Climate modeling of the late Cretaceous, incorporating data from fossil freshwater mussels and high-resolution simulations, revealed regional summer temperatures rarely exceeded 33 degrees Celsius. Despite this, T. rex exhibited consistently higher body temperatures than its environment, suggesting physiological heat retention.

The findings support the hypothesis of homeothermy in large non-avian dinosaurs, though the researchers distinguish this from definitive proof of endothermic metabolism. Gigantothermy—heat retention through body mass—offers an alternative explanation for stable internal temperatures in large ectotherms.

Computational models projecting thermal tolerance across 465 modern species indicate T. rex could inhabit diverse latitudes, including high-latitude regions like Alaska, with no thermal constraints from heat-humidity thresholds in simulated environments.

Limitations include potential seasonal bias from analyzing only growth-stage tooth tissue and the need for further fossil sampling to confirm widespread thermoregulatory capabilities. The study, published in Science Advances, contributes to ongoing research into dinosaur physiology and paleoecological distribution patterns.