Edmontosaurus ("Edmonton's Lizard"), as well as previously called Anatotitan ("Giant Duck"), was a large hadrosaur dinosaur, a member of the ornithischian dinosaurs and the most common groups of dinosaurs in the Late Cretaceous, from the Cretaceous. It was one of the last non-avian dinosaurs on Earth before the mass extinction event.
Edmontosaurus lived in western North America during the Late Cretaceous period from 76-65 million years ago. It was among the largest herbivores of its time and was also among the last member of the hadrosaur family of dinosaurs.
Edmontosaurus was a very large dinosaur with a massive 23 foot tail, arguably the largest members of the hadrosaur family. They measured over 39-43 feet (12-13 m) long, stood 13 feet tall at the hips, and weighed 4-6 tons, the size of a railroad box car.
It also had very large and wide hind legs and its front legs were short and chunky. Edmontosaurus had a large bill that resembled that of a modern duck - hence its original name. Inside its mouth was a large battery of teeth, designed to grind vegetation.
Like all herbivores, Edmontosaurus lived in small groups to large herds. When feeding, huge batteries of chewing teeth made short work of the vegetation they ate. Like the Iguanodon dinosaurs about some 20 million years earlier, Edmontosaurus walked on four legs but ran on two.
Despite its relatively large size, Edmontoasurus was preyed upon by predators, including the North American apex predator, Tyrannosaurus rex, as it viewed Edmontosaurus as a favorite prey item. However, although it had very few weapons of choice, Edmontosaurus did posses the ability to run rather quickly. Like its ancestors, it could run on its hind legs and could also swing its tail like the arm of a crane. However, its speed never always guaranteed it safety.