Diet: Allosaurus was a carnivore (meat-eater) who may have hunted in packs. In these groups, Allosaurus could have ambushed even the very large sauropods (like Diplodocus and Camarasaurus).

Anatomy: This bipedal predator was up to 38 feet (12 m) long and weighed roughly 1 to 5 tons. It had solid, heavy bones, long claws on its 3-fingered hands, and large, powerful jaws.

When Allosaurus Lived: Allosaurus was the biggest meat-eater during the late Jurassic period, about 154 to 144 million years ago.

Fossils: Allosaurus was named in 1877 by paleontologist Othniel C. Marsh, based on fragmentary remains. The first virtually complete Allosaurus skeleton was discovered by rancher M. P. Felch in 1883, in Colorado, USA. Over 60 Allosaurus fossils have been found.