The region is inhabited by 115 species (19 genera) of freshwater mussels in three families: Hyriidae, Mycetopodidae and Etheriidae.
South America is composed of six subregions. The Magdalena-Pacific Subregion (SA1; 5 gen., 12 spp., 5 endemic) is the area between the Isthmus of Panama and the Andes Mountains in the northwest. The Orinoco-Guayana Subregion (SA2; 10 gen., 31 spp., 17 endemic) includes the Orinoco basin east to the Guayanas. These basins are north of the Amazon Subregion (SA3; 16 gen., 37 spp., 12 endemic), composed of the whole Amazon Basin. The Atlantic coastal streams (including the São Francisco) in eastern Brazil comprise the São Francisco-Atlantic Subregion (SA4; 5 gen., 17 spp., 4 endemic). The Paraná-Paraguay Subregion (SA5; 11 gen., 63 spp., 42 endemic) is composed of all the rivers draining via the Rio de la Plata and the coastal streams of Uruguay and southern Brazil. Finally, the Patagonia Subregion (SA6; 2 gen., 3 spp., 2 endemic) includes southern Argentina and Chile.
Endemic species are marked with an asterisk (*).