T. rex ran a body temperature close to humans, fossil teeth study finds
Chemical clues in fossilized T. rex teeth indicate an average body temperature of about 36°C, close to that of humans and modern elephants.
Scientists have extracted a body-temperature reading from the teeth of Tyrannosaurus rex, finding that the dinosaur ran at roughly the same internal warmth as a human.
The analysis, published in the journal Science Advances, puts the predator's average body temperature at about 97 degrees Fahrenheit (36 degrees Celsius). That figure sits close to the range for people, between 97 and 99 degrees Fahrenheit (36 to 37 degrees Celsius), and matches that of present-day elephants.
Researchers have long debated how dinosaurs regulated their body heat. Early thinking held that they were slow, cold-blooded animals, but later evidence suggested that older dinosaurs were warm-blooded and could control their internal temperature. Most scientists now accept that T. rex was warm-blooded, yet fixing an exact core temperature for an extinct animal has proved difficult.
"We can't just use a thermometer to do that," said Jasmina Wiemann, a paleobiologist at Johns Hopkins University who was not involved in the study.
Previous attempts relied on growth patterns or bone clues, but no firm number emerged. The new work turned to teeth instead. Within tooth enamel, atoms cluster in patterns that vary with an animal's body temperature, giving researchers a chemical record to read.
"We figured out how warm the most famous animal of all, a T. rex, was," said co-author Aradhna Tripati, a geochemist at the University of California, Los Angeles.
Readings from three teeth produced the average of about 36 degrees Celsius. Wiemann said the result was lower than she had anticipated. Based on her earlier research, she had expected the dinosaur to run a few degrees hotter, closer to modern birds, which are dinosaurs' warm-blooded descendants.
Knowing the temperature helps build a picture of how T. rex lived. Tripati said that at 36 degrees Celsius the animal could have ranged across most of prehistoric North America, holding a stable internal temperature in both cooler and hotter regions. The finding may also offer clues about the prey it needed to hunt to sustain its energy needs.
The team says the method should now be tested on other dinosaurs to learn how warm or cold they ran. T. rex's temperature may have been one of the factors behind its rise as a dominant predator of the dinosaur age.
"There's lots of interesting, charismatic species that could be explored using this," said co-author Robert Eagle, a geobiologist at UCLA.