A study using fossilized T. rex teeth confirms the dinosaur had a body temperature of about 36°C, supporting the theory it was warm-blooded. The research, led by UCLA scientists, analyzed chemical bonds in enamel to estimate the temperature, offering new insights into dinosaur physiology.
Scientists have finally pinned down the body temperature of Tyrannosaurus rex, revealing the prehistoric predator likely ran warm—around 36°C, similar to modern humans. The breakthrough, published in Science Advances, relied on analyzing chemical bonds in fossilized teeth, a method refined over a decade to require just a few milligrams of enamel. This discovery adds critical evidence to the decades-long debate over whether dinosaurs were warm-blooded, a trait that would have allowed T. rex to thrive in diverse climates, including the frigid environments of ancient Alaska.
The Science Behind the Discovery
The research team, led by UCLA scientists Robert Eagle and Aradhna Tripati, used clumped-isotope analysis on two teeth from “Thomas,” a nearly complete T. rex skeleton housed at the Natural History Museum of Los Angeles County. This technique measures the arrangement of carbon and oxygen isotopes in tooth enamel, which form bonds at rates dependent on temperature. By drilling out minuscule samples—less than a milligram—scientists determined that T. rex’s body temperature was 36.3°C, significantly higher than cold-blooded reptiles but lower than modern birds.
The enamel chemistry recorded the temperature at which it formed, and 66 million years later we can read it,
said Tripati, a geochemistry professor at UCLA. The method’s precision stems from the durability of enamel, which resists chemical changes over millennia. Researchers spent over a decade refining the technique to reduce the fossil material needed by 90%, enabling analysis without damaging the specimen. Nobody can measure a T. rex tooth unless you can show them you only need a few milligrams,
Eagle noted.
Implications for Dinosaur Research
The findings align with growing evidence that many dinosaurs were warm-blooded, a theory bolstered by fossilized footprints in Alaska and other high-latitude regions. This was a warm-bodied organism, which really places new constraints on its behavior, its physiology, how it interacted with other species and how much food it needed,
Eagle said. A warm metabolism would have allowed T. rex to maintain activity in cold climates, challenging earlier assumptions that dinosaurs were sluggish, cold-blooded creatures.
Vertebrate paleontologist Thomas Holtz Jr., who was not involved in the study, called the method another way to examine the question.
Comparing T. rex’s temperature to that of cold-blooded crocodiles and clams from the same era, Holtz said the data gives high confidence
that the dinosaur was endothermic. The study also suggests T. rex’s physiology enabled it to inhabit a vast range, from modern-day Mexico to Alaska, though a high metabolism would have required a substantial food intake.
What This Means for Paleontology
The research opens new avenues for studying dinosaur physiology, with plans to apply the same technique to other species like Triceratops and Brachiosaurus. We have wondered about whether dinosaurs were warm-blooded or not literally since the first time dinosaurs got their name,
Holtz said, referencing Richard Owen’s 1842 description of Dinosauria. The study’s authors emphasize that while T. rex was warm-blooded, this does not necessarily mean all dinosaurs shared the trait.
The findings also highlight the evolving understanding of dinosaur biology. For decades, scientists relied on skeletal structure and biomechanics to infer metabolism, but this study offers a direct, chemical measurement. For an animal this famous, it is remarkable how little we actually knew,
Tripati said. The research underscores the value of interdisciplinary approaches, merging geochemistry with paleontology to unlock secrets buried in ancient fossils.
As paleontologists continue to refine these methods, the line between reptile and bird-like physiology in dinosaurs grows clearer.