Corosaurus is known from the holotype UW 5485, a partial skeleton which includes the skull.[1] Later, the referred specimens YPM 41030-41068, FMNH PR 135, FMNH PR 1368-1369, FMNH PR 242-246 and FMNH PR 1382-1383 were described by Glenn William Storrs in 1991. All specimens were collected in Jackson Canyon, Natrona County, from the Chugwater Group of the Alcova Limestone Formation, dating to the late Olenekian stage of the late Early Triassic, about 247.4-245 million years ago.[3] After a revision of the holotype and referred material of Corosaurus, Olivier Rieppel found Corosaurus to be the sister-taxon to a clade comprising Cymatosaurus, Pistosaurus and Plesiosauria.