The purpose of this application, under Articles 68 and 75 of the Code, is to conserve the generic name Cuvieronius Osborn, 1923, long and widely applied to extinct South American gomphotheriid proboscideans, by setting aside all previous type species fixations and designating Mastotherium hyodon Fischer, 1814 as the type species of Cuvieronius and by designating a neotype for that species. Because M. hyodon has long and universal (though incorrect) usage as the type species of Cuvieronius and because the type specimen of M. hyodon is unidentifiable, the type species and neotype designations are proposed to promote the stability and universality of nomenclature.