Elasmosaurus was a large marine reptile that lived during the Late Cretaceous (about 80 million years ago) in a shallow sea that once covered what is now central North America. It belonged to a group of reptiles called plesiosaurs which are characterized by the possession of a very long neck, small head, turtle-shaped body with flippers rather than legs, and a short tail, all of which are represented on this Elasmosaurus toy. History: The first Elasmosaurus fossil was described by the famous American paleontologist Edward Drinker Cope in 1868. Cope was a fossil lizard expert, and this led to a curious mistake - while in a hurry to publish his description of Elasmosaurus, he put the skull on the end of the tail, thinking that it was the neck. Cope spend a lot of time and money trying to buy back all of the copies of his original description so that he could correct his mistake and put the head on the right end of the animal. Scientific Name: Elasmosaurus, which means thin plate.