Allosaurus fragilis was a large theropod from the Late Jurassic of North America (Morrison Formation). It measured about 7.5–8.5 meters in length and weighed roughly 1.3–2 tons, being one of the main apex predators of its ecosystem.

It had a large but lightly built skull with long, laterally compressed, serrated teeth adapted for slicing flesh rather than crushing bone. The forelimbs were relatively large for a theropod of its size, with three-fingered hands and large curved claws. It likely hunted large herbivorous dinosaurs using slashing attacks and repeated strikes rather than a single powerful bite.