T. rex teeth indicate it ran as warm as an elephant

The estimated body temperature of T. rex is now comparable to that of modern elephants, indicating a metabolically active physiology rather than a sluggish reptile.

Researchers have analyzed T. rex teeth to estimate its body temperature, suggesting it was warm-blooded, similar to modern elephants. Using a technique called clumped isotope thermometry on carbonate minerals in tooth enamel, scientists measured the ratio of heavy isotopes of carbon and oxygen to determine the temperature at which the enamel formed. The analysis of three T. rex teeth indicated an average body temperature of approximately 36.3° Celsius, falling within the range of large mammals like elephants and significantly warmer than contemporary crocodilians, which averaged around 30.9° Celsius. This finding challenges earlier perceptions of T. rex as a sluggish reptile and supports the view of it as an active, endothermic animal capable of managing its own body heat. The study also used climate modeling to show that T. rex was consistently warmer than its environment and could have inhabited various climate zones across North America.

The new dental thermometry method, utilizing clumped isotope thermometry, overcomes limitations of previous studies by decoupling body temperature from ambient water composition, offering a more reliable measure of dinosaur physiology. This technique, applied to T. rex teeth, yielded temperatures comparable to modern endotherms like elephants, suggesting that these giant predators were not solely reliant on external heat sources. This finding contributes to a growing body of evidence that supports a more active, bird-like metabolism for T. rex, prompting a re-evaluation of its ecological role and behavior.

The research indicates that T. rex's warm-blooded nature allowed it to maintain a stable body temperature across a wide range of environmental conditions, potentially enabling its widespread distribution across North America. While the study acknowledges the possibility of seasonal bias due to limited samples, the consistent results across multiple teeth strengthen the argument for homeothermy. Future research using the same methodology aims to explore the thermal physiology of other dinosaur species, potentially revealing a broader evolutionary trend toward endothermy in prehistoric reptiles.