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. 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 31 to 200 centimetres (1.0–6.6 ft) 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.
Potamotrygonidae
Potamotrygon histrix is one of the most southernly distributed river stingrays, being found in the Río de la Plata Basin
Potamotrygon henlei and its close relatives (e.g., P. leopoldi) mainly feed on snails in the wild, but easily adapt to a more generalized diet in captivity
As in other rays, this Plesiotrygon iwamae is easily identified as male by its claspers, the pair of elongated structures at the base of the tail
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown the myliobatiforms to be a monophyletic group, and its more derived members evolved their highly flattened shapes independently of the skates.
Myliobatiformes
Camouflaged porcupine ray