Research carried out on austral plesiosaurs from the Weddellian Biogeographic Province in the decade since the last attempt to characterise the New Zealand elasmosaurid, Mauisaurus haasti Hector, 1874 (On the Fossil Reptilia of New Zealand. Transactions and Proceedings of the New Zealand Institute 6: 333-358), has prompted a reappraisal of this taxon and a new consideration of its relationships. The hypodigms used in previous descriptions of the species are shown to include specimens from a number of different taxa, and the defining apomorphy of Mauisaurus, a hemispherical capitulum on the femur, has now been observed in specimens known to belong to different clades. Mauisaurus is now regarded as nomen dubium with possible affinities with the Subfamily Aristonectinae. A re-assessment of the most complete specimen previously assigned to Mauisaurus suggests it is a typical long-necked elasmosaurid closely comparable to Tuarangisaurus keyesi Wiffen and Moisley, 1986 (Late Cretaceous reptiles (Families Elasmosauridae and Pliosauridae) from the Mangahouanga Stream, North Island, New Zealand. New Zealand Journal of Geology and Geophysics 29: 205-252).