The genus Eretmosaurus was erected for 'Plesiosaurus' rugosus by Seeley (1874). Eretmosaurus is a rogue taxon in cladistic analyses and researchers have been in disagreement about its taxonomic affinity. Eretmosaurus has been included in several different families: the Rhomaleosauridae based on the anatomy of its girdles (Persson 1963); the Pliosauridae (Brown 1981), the…