English: Allosaurus jimmadseni is the most abundant large theropod from the Late Jurassic of North America. It was a bipedal predator at the top of its food chain, with a robust skull equipped with dozens of sharp, serrated teeth. Allosaurus was able to open its jaws to a 90 degree angle, the widest known gape of any dinosaur, allowing it to attack much larger prey. Allosaurus could grow to about 9 m in length, and weighed around 2.5 t. It is hypothesized that Allosaurus exhibited cooperative social behavior and hunted in packs, though it is possible that their social interactions were aggressive and competitive, rather than cooperative.