Sauropterygia

From Ancient Greek, literally "lizard flippers".

†Sauropterygia

1. A taxonomic superorder within the class Reptilia – extinct 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. They are united by a radical adaptation of their pectoral girdle, designed to support powerful flipper strokes.