Home > Diorama > Dinosaur Explorer > Allosaurus The Allosaurus (which literally means "different lizard") was first discovered in 1877 by Othniel Marsh and was one of the largest carnivorous dinosaurs to have ever lived. Allosaurus lived 50 million years before Tyrannosaurus Rex, during the late Jurassic Period in North America. These dinosaurs measured up to 38 feet long, 16½ feet tall and could weigh well over 3000 pounds. Its short arms had three-fingered hands and claws which measured up to 6 inches in length. Its powerful jaws contained a set of extremely sharp serrated teeth, which measured up to 4 inches in length. One Allosaurus can be found in the diorama at Universe of Energy and is located in the "fight scene" atop a rock ledge above the vehicles on the right side.