Madagascar is widely recognized as a biodiversity hotspot, but the freshwater bivalves have received only limited recent attention. Based upon examination of records from 15 major museums and a literature review, at least nine species of freshwater mussels (Mollusca: Bivalvia: Unionoida) have been reported from either Madagascar or the Mascarene Islands (specifically, Reunion or Mauritius) in the Indian Ocean, east of Africa. The quality of the data, however, is generally poor. Seven of those species records are regarded as either erroneous reports of taxa known from other regions or as nomina dubia. No records from the Mascarenes are considered to be valid. The two remaining species, Etheria elliptica Lamarck 1807 and Unio geayi Germain 1911 (= Coelatura geayi) are both from Madagascar, and the latter is discussed in the context of two alternative hypotheses for the origin of the family Unionidae, nicknamed “Out of Africa” and “Into Africa.” Germainaia gen. nov. is introduced for Unio geayi to emphasize the distinction of that species from other Afrotropical freshwater mussel lineages. The possibility that Germainaia may represent the Hyriidae in Madagascar is discussed, but the new genus is left incertae sedis at the family-level in the absence of complete data.

New taxon: Germainaia Graf and Cummings