Elasmosaurus platyurus is perhaps the most iconic of the plesiosaurs, a group of marine reptiles which swam in the oceans throughout the Mesozoic Era. Existing around 80 million years ago during the Cretaceous Period, Elasmosaurus is known to have hunted in the Western Interior Seaway which once submerged central North America. Its elongated neck would have run over twenty feet in length.
By the way, the bumpy skin and glowing bioluminescent spots portrayed here are speculative features rather than known for certain.