Allosaurus is a genus of large theropod dinosaur that lived 155 to 145 million years ago, in the late Jurassic period (Kimmeridgian to Tithonian). The name Allosaurus means “different lizard”. The first remains that can definitely be ascribed to this genus were described in 1877 by Othniel Charles Marsh. Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of sharp, serrated teeth. The skull of Allosaurus is well documented, although resources are scattered. The seminal skeletal reference of Madsen 1976 only partially documents the skull.