Tyrannosaurus rex was a hottie with a body temperature similar to our own, according to a new analysis of their teeth. MThe finding supports the idea that T. rex was a fast, energetic predator and scavenger, not an animal that basked in the sun to gain energy like most modern-day reptiles.

T. rex, which lived between about 68 million and 66 million years ago, at the end of the Cretaceous period (143.1 million to 66 million years ago), was one of the largest carnivorous dinosaurs that ever lived.

Previous studies have already suggested that T. rex and its relatives were warm blooded, but now scientists have estimated the dinosaur's body temperature for the first time by studying different isotopes, or forms, of the same chemical elements in the enamel of three T. rex teeth from specimens found in the Hell Creek Formation in Montana.

Rare, heavy isotopes of carbon and oxygen bond together differently in growing tooth enamel depending on the temperature. The number of bonds formed between these rare isotopes is greater at cooler temperatures than it is at warmer temperatures, which means warm-blooded, or endothermic animals, that can regulate their own body temperature, have fewer of these chemical bonds in their teeth than cold-blooded, or ectothermic, animals, which rely on their environment for warmth...