Allosaurus

Allosaurus, late Jurassic carnivorous dinosaur of the W United States. Specimens of 30 to 40 ft (9 to 12 m) have been found. It had stong hind legs, smaller sharply clawed forelimbs, two small horns directly above the eyes, and expandable jaws that could widen to consume large pieces of meat.

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Allosaurus

Large carnivorous dinosaur of a group similar to the tyrannosaurs, found as fossils primarily in Late Jurassic rocks of North America. It weighed 2 tons (1,800 kg) and grew to 35 ft (10.5 m) long. Its well-developed tail, half of its total body length, probably functioned as a counterbalance for the body. Allosaurus walked on its two hind limbs and probably used the much smaller forelimbs for grasping. Equipped with powerful, flexible jaws, allosaurs likely preyed on medium-sized dinosaurs; they were possibly scavengers that hunted in groups. Some related allosaurs (Giganotosaurus, Carcharodonotosaurus) may have been larger than Tyrannosaurus rex.