(syn. Mergus Ϯ Auckland Island Merganser M. australis) Gr. προ pro before, related; genus Mergus Linnaeus, 1758, merganser; "Genus PROMERGUS, nov. Differs from the genus Mergus (type M. merganser Linné) in its longer and more slender bill and shorter toes, but especially in having the sexes alike in coloration; in Mergus the depth of the culmen at the frontal feathers is more than one-third its length, while in Promergus the depth is less than one-fourth the length. Type: P. australis (Hombron & Jacquinot)." (Mathews & Iredale 1913).