Allosaurus ("other lizard") was one of the biggest carnivorous dinosaurs before the tyrannosaurids appeared some 50 million years later. Allosaurus's long, muscular hind limbs supported a body weighing two tonnes or more. The huge but lightweight skull consisted largely of bony struts, with bony ridges above the eyes. The immennse, expandable jaws had long, curved, saw-edged teeth. A thick, S-curved neck supported the head, and a long, deep tail counterbalanced the heavy front end of this terrifying theropod.