Polycotylus is a genus of plesiosaur within the family Polycotylidae.[1] The type species is P. latippinis and was named by American paleontologist Edward Drinker Cope in 1869. Eleven other species have been identified. The name means 'much-cupped vertebrae', referring to the shape of the vertebrae. It lived in the seas of North America, toward the end of the Cretaceous.[2] One fossil preserves an adult with a single large fetus inside of it, indicating that Polycotylus gave live birth, an unusual adaptation among reptiles.
Description[]
Like all plesiosaurs, Polycotylus was a large marine reptile with a short tail, large flippers, and a broad body. It has a short neck and a long head, and was about 5 metres (16 ft) long.[3] It has more neck vertebrae than other polycotylids, however. Polycotylus is thought to be a basal polycotylid because it has more vertebrae in its neck (a feature that links it with long-necked ancestors) and its humerus has a more primitive shape. The long ischia of the pelvis are a distinguishing feature of Polycotylus, as are thick teeth with striations on their surfaces, a narrow pterygoid bone on the palate and a low sagittal crest on top of the skull.
History[]
Edward Drinker Cope named Polycotylus from the Niobrara Formation in Kansas in 1869. The holotype bones from which he based his description were fragmentary, representing only a small portion of the skeleton. A more complete skeleton was later found in Kansas and was described in 1906. A nearly complete skeleton was found in 1949 from the Mooreville Chalk Formation in Alabama, but was not described until 2002.