Elasmosaurus

Elasmosaurus is an extinct genus of plesiosaurs with an exceptionally long neck, known from Late Cretaceous marine deposits in North America.

Plesiosauria: Plesiosauria is an extinct clade of marine reptiles with four flippers and compact bodies. Elasmosaurus belongs to this clade, whose body plan frames its anatomy.
Elasmosaurus platyurus: Elasmosaurus platyurus is the type species of the genus, described from a fossil found in Kansas. This species anchors the genus and its best-known early fossil history.
Plesiosaur locomotion: Plesiosaur locomotion was powered by coordinated strokes of the fore and hind flippers. This propulsion system carried Elasmosaurus through the sea despite its long neck.
Mosasaur: A mosasaur is an extinct marine squamate with an elongated body, paddle-like limbs, and powerful tail. Mosaurs were contemporaneous marine predators, but they were not plesiosaurs and swam differently.
Elasmosauridae: Elasmosauridae is a plesiosaur family characterized by especially long necks and numerous neck vertebrae. Elasmosaurus is a member of the family named for its distinctive long-necked form.
Samuel Wendell Williston: Samuel Wendell Williston was an American paleontologist and physician who studied fossils of the American West. He corrected the early reconstruction of Elasmosaurus by recognizing that its long vertebral series belonged to the neck.
Plesiosaur feeding: Plesiosaur feeding involved capturing prey with jaws, with strategies inferred from anatomy and fossil evidence. The skull and neck inform hypotheses about how Elasmosaurus approached and caught prey.
Pliosaur: A pliosaur is a plesiosaur with a short neck, large head, and powerful swimming limbs. Pliosaurs show the short-necked body plan contrasted with Elasmosaurus’s extreme neck.
Plesiosaur neck: A plesiosaur neck is the chain of cervical vertebrae extending from the shoulders to the skull. Its extreme length is among Elasmosaurus’s most striking anatomical features.
Edward Drinker Cope: Edward Drinker Cope was an American paleontologist who described many fossil vertebrates during the nineteenth century. Cope named Elasmosaurus in 1868 and initially placed its skull at the wrong end of the skeleton.

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