FACT SHEET: Allosaurus

NAME: ALLOSAURUS (AL-oh-SAUR-us), meaning: "Different Lizard" SIZE: 38 feet long, 16 feet tall (the size of a school bus), weighed 3 tons TYPE OF DIET: Carnivore (large plant-eating dinosaurs) WHEN: Late Jurassic period (154 - 144 million years ago) WHERE: Colorado, North America

Allosaurus was a big, carnivorous dinosaur, meaning that it ate meat. It was the largest carnivore in North America during the late Jurassic period. Allosaurus was about 38 feet long and 16 feet tall. It weighed about 3 tons. That’s larger than a school bus! There were lots and lots of Allosaurus during the late Jurassic period. In fact there were more Allosaurus than any other predator in North America. Allosaurus had a big, heavy tail, a bulky body, and thick bones. Its hind legs were thick and powerful but its front legs were tiny. It used its small arms to grab things. It had large, powerful jaws with long, sharp, teeth. Its teeth were serrated like a saw and up to four inches long. The name Allosaurus means “different lizard”. It got its name because of its unusual vertebrae, which are bones in its back and neck. No other dinosaur was built quite the same way. Most dinosaurs have gastralia that come out of the backbone. Gastralia are ribs that hang over a dinosaur’s belly. They are thin and fragile, but help protect a dinosaur’s insides, like its heart and lungs. In the Allosaurus, these bones were growing from the skin in its belly instead. Allosaurus was a fierce hunter and probably ate large, plant-eating dinosaurs, like Stegosaurus and Iguanodon. But it was probably not a very fast runner. Big bipedal dinosaurs were so heavy that if they fell they could really hurt themselves. The first whole Allosaurus skeleton was discovered in 1883, in Colorado, North America. They were often found together at the same site. Because of this we believe that Allosaurus may have hunted in groups.