T. rex ran warm: new analysis reveals dinosaur body temperature
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Researchers at the University of California, Los Angeles, and the Natural History Museum of Los Angeles County determined that Tyrannosaurus rex maintained a body temperature of approximately 97 degrees Fahrenheit. The team developed a technique to measure fossilized tooth enamel, analyzing rare isotopes of carbon and oxygen to estimate the dinosaur’s internal temperature.
This is the first direct evidence showing T. rex was warm-blooded, supporting the idea that the predator had a fast metabolism and could thrive in colder environments like ancient Alaska. For over a century, scientists have used fossil evidence to understand T. rex biology. Previous discoveries indicated the dinosaur could withstand cold conditions, suggesting a shift away from the cold-bloodedness common in reptiles.
The UCLA team refined their temperature-measuring method over a decade, reducing the amount of fossil material needed for testing. This allowed the Natural History Museum to provide samples from “Thomas,” a complete T. rex skeleton on display. The researchers drilled into two of Thomas’s teeth, collecting enamel that they dissolved in acid to release carbon dioxide gas. A mass spectrometer then measured isotope ratios within the gas, revealing the dinosaur’s body temperature.
Modern reptiles generally maintain temperatures around 82-86 degrees Fahrenheit, while birds average 104-109 degrees Fahrenheit. T. rex’s 97-degree temperature places it closer to warm-blooded mammals than to today’s reptiles. The study also analyzed a 66-million-year-old crocodilian fossil from the same location, finding a temperature of 86 degrees Fahrenheit, confirming the accuracy of the method. This finding supports the theory that T. rex’s warm-bloodedness helped it survive and thrive in a wider range of climates.
