Allosaurus - Meaning: Other Lizard

Allosaurus (AL-oh-saw-russ) was a large bipedal (active on two legs) carnivorous dinosaur up to 12 metres (39 ft) long. It was named 'different lizard' because its vertebrae were different from those of all other dinosaurs.

The name comes from the Greek meaning 'strange' or 'different'. It was the most common large predator in what is now North America, 155 to 145 million years ago, active in the late Jurassic period.

It shared the landscape with several genera of giant sauropods such as Apatosaurus, Diplodocus and Camarasaurus as well as other herbivores such as Stegosaurus and Camptosaurus, all of which may have been potential prey.

More scant finds of a smaller species similar to Allosaurus and dating from the Early Cretaceous of North America and Australia, indicate that this versatile hunter might have survived the mass extinction at the end of the Jurassic period.

Allosaurus was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs, with an average length of 9 metres (30 feet). Its most distinctive feature was a pair of blunt horns, just above and in front of the eyes. Although short in comparison to the hindlimbs, the forelimbs were massive and bore large, eagle-like claws. The skull showed evidence of being composed of separate modules, which could be moved in relation to one another, allowing large pieces of meat to be swallowed. The skeleton of Allosaurus, like other theropods, displayed bird-like features, such as a furcula (wishbone) and neck vertebrae hollowed by air sacs.

Allosaurus is the most common theropod in the vast tract of dinosaur-bearing rock in the American Southwest known as the Morrison Formation. Remains have been recovered in Montana, Wyoming, South Dakota, Colorado, Oklahoma, New Mexico and Utah, in the United States. There have also been finds in Portugal. Allosaurus shared the Jurassic landscape with several other theropods, including Ceratosaurus and the massive Torvosaurus.