Stock Photo - 'Elasmosaurus dinosaur.  Artwork of Elasmosaurus, a marine dinosaur (plesiosaur) coming ashore ... .  Elas- mosaurus ('plated reptile') had a long neck with a relatively  small  head  and  a mouth  lined  with teeth.  It was probably a fish-eater,   using  its neck  to  dart its head at prey.  It was propelled through the water  by  four  powerful  paddle-like limbs  which  it  flapped  up  and  down  like the paddles of a modern-day turtle. Elasmosaurus prob- ably came ashore to lay its eggs.  Dinosaurs lived during the  Mesozoic  era  (65-225  million  years ago). Elasmosaurus was described in 1868, although the first  reconstruction  mistakenly  placed  its head on the end of its relatively short tail.