Plesiosaur

Plesiosaurs were large marine reptiles that lived during the Mesozoic period. Despite being large reptiles, they were not a type of dinosaur.

There are two major kinds of plesiosaur. One type is characterized by having a large head and a short neck, while the other group is small-headed and long-necked. The former are known as pliosaurs. Of the latter group there are three kinds: the plesiosaurid, the cryptoclidids and the elasmosaurs.