Allosaurus ( IPA : /?æl?'s???s/ ) was a large (up to 9.7 m long) bipedal carnivorous dinosaur . The name Allosaurus comes from the Greek allos/a???? , meaning 'strange' or 'different' and saurus/sa???? , meaning 'lizard' or 'reptile'. [1] It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at the time of its discovery. Allosaurus was the most common large predator in the Morrison Formation of what is now North America , 155 to 145 million years ago , 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.
