Fossils of Tyrannosaurus rex are found in rocks from the last three million years of the Cretaceous Period. It was among the last dinosaurs to exist before the Cretaceous-Tertiary Extinction event, 65 million years ago.

Tyrannosaurus was a carnivore that walked on two legs with a massive skull balanced by a long, heavy tail. Tyrannosaurus had a large, powerful hind limbs with three toes, each of which would have ended in a claw like this one.