Elasmosaurus.
Elasmosaurus was a large marine reptile in the order Plesiosauria. The genus lived about 80.5 million years ago, during the Late Cretaceous. The first specimen was sent to the American paleontologist Edward Drinker Cope after its discovery in 1867 near Fort Wallace, Kansas. Only one incomplete skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species, E. platyurus, is recognized today. Measuring 10.3 meters (34 ft) long, the genus had a streamlined body with paddle-like limbs or flippers, a short tail, and a small, slender, triangular head. With a neck around 7.1 meters (23 ft) long, Elasmosaurus was one of the longest-necked animals to have lived, with the largest number of neck vertebrae known, 72. It probably ate small fish and marine invertebrates, seizing them with long teeth. Elasmosaurus is known from the Pierre Shale formation, which represents marine deposits from the Western Interior Seaway.
