A 66-million-year-old tooth reveals T. rex was nearly as warm as a human

For more than a century, scientists have tried to reconstruct the biology of Tyrannosaurus rex from bones, teeth, footprints, and other traces left behind more than 60 million years ago. Fossils discovered as far north as Alaska have suggested that T. rex could tolerate cold conditions, adding to evidence that the giant dinosaur was moving away from the cold-blooded physiology of many reptiles and toward the warm-blooded metabolism seen in birds.

Now scientists have done something that once seemed impossible: they have effectively taken T. rex 's temperature.

Researchers at UCLA developed a method for estimating body temperature from fossilized teeth and applied it to specimens held by the Natural History Museum of Los Angeles County. Their results indicate that T. rex maintained a body temperature of about 97 degrees Fahrenheit, remarkably close to that of humans.