Potamotrygonidae

River stingrays or freshwater stingrays are Neotropical freshwater fishes of the family Potamotrygonidae in the order Myliobatiformes, one of the four orders of batoids, cartilaginous fishes related to sharks. They are found in rivers in tropical and subtropical South America (freshwater stingrays in Africa, Asia and Australia are in another family, Dasyatidae). A single marine genus, Styracura, of the tropical West Atlantic and East Pacific are also part of Potamotrygonidae. They are generally brownish, greyish or black, often with a mottled, speckled or spotted pattern, have disc widths ranging from and venomous tail stingers. River stingrays feed on a wide range of smaller animals and the females give birth to live young. There are more than 35 species in five genera.

== Evolution == Potentially the oldest known member of the family is the extinct potential styracurine Atlantitrygon, known from fossil teeth recovered from the Late Paleocene of Senegal. The oldest definitive member of this family, and also the oldest from freshwater habitats, is Potamotrygon ucayalensis from the middle Eocene of Peru.