T. Rex Teeth Reveal Human-Like Body Temperature

UCLA scientists reported Wednesday the first measurement of T. rex body temperature, about 97°F (36°C), by analyzing enamel from three fossil teeth at the Natural History Museum of Los Angeles County. They measured rare carbon-13 and oxygen-18 isotope bonds that form depending on temperature. The Science Advances study used a UCLA method refined to require 90% less material than a decade ago. "No one's been able to make a temperature measurement like this before," co-author Robert Eagle said. "We found T. rex was 36 Celsius (97 Fahrenheit), about the same as humans. The temperature is about what I would have guessed — higher than a reptile or a slow mammal like a sloth, but lower than an avian." Crocodilian fossils from the Montana Hell Creek site read about 86°F, like modern reptiles at 82–86°F, ruling out alteration; birds are 104–109°F. Alessandro Chiarenza said models show a range from Mexico to Alaska 66 million years ago. Aradhna Tripati said: "For an animal this famous, it is remarkable how little we actually knew." Teeth indicate T. rex ran warmer than the environment and could reach the Arctic, where its fossils occur but cold-blooded reptiles' do not. National Science Foundation grants aided the research. What is contested: none found.