Allosaurs were a family or a clade of theropoddinosaurs. Although they originated in the Northern Hemisphere, the last allosaurs were found in the south. The members of this group were characterized by large, well-developed front limbs, armed with powerful claws, and long and relatively narrow jaws, studded with thin, blade-like teeth - perfect for slicing teeth but useless against armored skin and bone, unlike the teeth of Tyrannosaurus rex.
Allosaurs were primarily hunters of giant sauropod dinosaurs like Diplodocus and Argentinosaurus. To bring them down, allosaurs often hunted in loose packs. However, when those giants died out, so did the allosaurs and carchardontosaurs.