Artist's restoration of the sauropterygian Plesiosaurus

Sauropterygia (" lizard flippers") is an extinct, diverse taxon of aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Mesozoic before they became extinct at the end of that era. Sauropterygians are united by a radical adaptation of their pectoral girdle, designed to support powerful flipper strokes. Some later sauropterygians, such as the pliosaurs, developed a similar mechanism in their pelvis.
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