|Ocellate river stingray, Potamotrygon motoro|
River stingrays or freshwater stingrays are Neotropical freshwater fishes of the Potamotrygonidae family in the order Myliobatiformes, one of the four orders of batoids, cartilaginous fishes related to sharks. River stingrays are found in rivers in South America draining into the Caribbean Sea and the Atlantic Ocean as far south as the River Plate in Argentina. Each river system has its own endemic stingrays. They are generally pale brown, variously mottled or speckled, have discs ranging from 25 to 150 centimetres (1 to 5 ft) in diameter and venomous caudal stings. There are about twenty-eight species in four genera.
They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina. Generally, each species is native to a single river basin, and the greatest species richness can be found in the Amazon.
River stingrays are almost circular in shape, and range in size from Potamotrygon schuhmacheri, which reaches 25 centimetres (9.8 in) in diameter, to the short-tailed river stingray, P. brachyura, which grows up to 1.5 metres (4.9 ft) in diameter. The upper surface is covered with denticles (sharp tooth-like scales). Most species are brownish or greyish and often have distinctive spotted or mottled patterns, but a few species are largely blackish with contrasting white spots.
They have a venomous caudal sting, and are one of the most feared freshwater fishes in the Neotropical region, sometimes more feared than piranhas and electric eels. However, they are not dangerous unless stepped on or otherwise threatened.
River stingrays are the only family of batoids completely restricted to fresh water habitats. While there are true freshwater species in the family Dasyatidae, for example Himantura chaophraya, the majority of species in this family are saltwater fish.
- Genus Heliotrygon Carvalho & Lovejoy, 2011
- Genus Paratrygon A. H. A. Duméril, 1865
- Genus Plesiotrygon Rosa, Castello & Thorson, 1987
- Genus Potamotrygon Garman, 1877
- Potamotrygon amandae Loboda & M. R. de Carvalho, 2013
- Potamotrygon boesemani Rosa, M. R. de Carvalho & Almeida Wanderley, 2008 (Emperor ray) 
- Potamotrygon brachyura (Günther, 1880) (Short-tailed river stingray)
- Potamotrygon constellata (Vaillant, 1880) (Thorny river stingray)
- Potamotrygon falkneri Castex & Maciel, 1963 (Largespot river stingray)
- Potamotrygon henlei (Castelnau, 1855) (Bigtooth river stingray)
- Potamotrygon humerosa Garman, 1913
- Potamotrygon hystrix (J. P. Müller & Henle, 1834) (Porcupine river stingray)
- Potamotrygon leopoldi Castex & Castello, 1970 (White-blotched river stingray)
- Potamotrygon limai Fontenelle, J. P. C. B. da Silva & M. R. de Carvalho, 2014
- Potamotrygon magdalenae (A. H. A. Duméril, 1865) (Magdalena river stingray)
- Potamotrygon marinae Deynat, 2006
- Potamotrygon motoro (J. P. Müller & Henle, 1841) (Ocellate river stingray)
- Potamotrygon ocellata (Engelhardt, 1912) (Red-blotched river stingray)
- Potamotrygon orbignyi (Castelnau, 1855) (Smoothback river stingray)
- Potamotrygon pantanensis Loboda & M. R. de Carvalho, 2013
- Potamotrygon schroederi Fernández-Yépez, 1958 (Rosette river stingray)
- Potamotrygon schuhmacheri Castex, 1964 (Parana River stingray)
- Potamotrygon scobina Garman, 1913 (Raspy river stingray)
- Potamotrygon signata Garman, 1913 (Parnaiba River stingray)
- Potamotrygon tatianae J. P. C. B. da Silva & M. R. de Carvalho, 2011
- Potamotrygon tigrina M. R. de Carvalho, Sabaj Pérez & Lovejoy, 2011 (Tiger ray) 
- Potamotrygon yepezi Castex & Castello, 1970 (Maracaibo River stingray)
- Compagno, L. J. V. & S. F. Cook (1995) "The exploitation and conservation of freshwater elasmobranchs: status of taxa and prospects for the future". In: The Biology of Freshwater Elasmobranchs. Oetinger, M. I. & Zorzi, G. D. (eds.). Journal of Aquariculture & Aquatic Sciences, 7: 62–90.
- Freshwater Stingrays (Potamotrygonidae): status, conservation and management challenges CITES. AC20 Inf. 8.
- De Carvalho, M.R. and N.R. Lovejoy (2011). "Morphology and phylogenetic relationships of a remarkable new genus and two new species of Neotropical freshwater stingrays from the Amazon basin (Chondrichthyes: Potamotrygonidae)". Zootaxa (2776): 13–48.
- Loboda, T.S.; de Carvalho, M.R. (2013). "Systematic revision of the Potamotrygon motoro (Müller & Henle, 1841) species complex in the Paraná-Paraguay basin, with description of two new ocellated species (Chondrichthyes: Myliobatiformes: Potamotrygonidae)" (PDF). Neotropical Ichthyology 11 (4): 693–737. doi:10.1590/s1679-62252013000400001.
- Rosa, de Carvalho & Wanderley (2008). "Potamotrygon boesemani (Chondrichthyes: Myliobatiformes: Potamotrygonidae), a new species of Neotropical freshwater stingray from Surinam". Neotropical Ichthyology 6 (1): 1–8. doi:10.1590/S1679-62252008000100001.
- Fontenelle, J.P., Da Silva, J.P.C.B. & De Carvalho, M.R. (2014): Potamotrygon limai, sp. nov., a new species of freshwater stingray from the upper Madeira River system, Amazon basin (Chondrichthyes: Potamotrygonidae). Zootaxa, 3765 (3): 249–268.
- de Carvalho, Perez & Lovejoy (2011). "Potamotyrgon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yepez, 1958 (Chondrichthyes: Potamotrygonidae)". Zootaxa 2827: 1–30.
8. Ross, Richard (1999) Freshwater Stingrays, Aqualog Special,p49 9. Ross, Richard (2000) Freshwater Rays, Aqualog, p140
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