The freshwater anomuran crabs of the family Aeglidae are all restricted to southern South America occurring in Chile, Brazil, Bolivia, Uruguay, Paraguay, and Argentina. The family consists of a single genus, Aegla, containing 63 currently described species. There are another 5-10 known yet undescribed species to complement this diversity. The aeglids occur in freshwater lakes, streams, rivers, and in caves with freshwater. The origin of the family appears to be from marine ancestors from the Pacific invading streams in Chile about 75 mya radiating both in Chile and again on the eastern side of the Andes, particularly in Brazil. Of the 63 species, 23 or 36.5% are considered under threat and are in need of conservation action.