56531 Plesiotrygon iwamae Rosa, Castello & Thorson, 1987 Potamotrygonidae River stingrays Potamotrygoninae Myliobatiformes Elasmobranchii Long-tailed river stingray South America: Upper to lower Amazon River basin, from Ecuador to Belém, Brazil, in the Napo, Solimões, Amazonas and Pará rivers.