Allosaurus, the "Different Lizard," provides a "different" example of a ferocious predator than that of the Tyrannosaurus. Contrasting with the T. rex, the Allosaurus measured only three meters tall, just under twice the height of a human. It was still quite long at a maximum of 9-10  meters. Its notable skull ridges had several functions, such as acting as sun-shades and display items. Curiously, many skull fossils found exhibit odd imperfections, providing valuable insight into the paleo- pathology of dinosaurs and its  possible effects on creatures.  Living at the top of its food chain, the menacing claws and jaws of the Allosaurus made it quite the predator long before the time of the Tyrannosaurus. Abundantly  found in the Morrison Formation, it survived by preying upon large  herbivores and possibly even some  predators. It prowled the semiarid  environments of present day America  and Portugal alongside other  predators like Ceratosaurus and  Torvosaurus, but the three likely  held separate niches. Living from the Kimmeridgian to early Tithonian  eras of the Jurassic, Allosaurus had a delectable selection of prey.  Paleontologists have found evidence  that it hunted Stegosaurus and  other members of its family for food  and likely scavenged sauropod  carcasses.