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Plesiosauria (plesiosaurs; subclass Euryapsida, order Sauropterygia) A suborder of aquatic reptiles which enter the fossil record in the late Triassic and which are common in many Jurassic and Cretaceous sediments. In appearance they have been likened to ‘a snake strung through the body of a turtle’, and some grew up to 15 m in length. There were also shortnecked types, as well as the swan-necked. The former are defined as the superfamily Plesiosauroidea, the latter as the superfamily Pliosauroidea, the latter as the superfamily Pliosauroidea, the two making up the suborder.

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