ABSTRACT

The family Potamotrygonidae was described by Garman (1877) to include freshwater stingrays restricted to the South American continent. This is the most speciose extant group of elasmobranchs living in fresh waters, with approximately 20 valid species (Charvet-Almeida et al. 2002; de Carvalho, Lovejoy, and Rosa 2003; Rosa, de Carvalho, and Wanderley 2008). Potamotrygonid stingrays occur in most of the major river systems of South America draining to the Atlantic Ocean and the Caribbean Sea, with the exception of the São Francisco River and all coastal drainages south of the Parnaíba River in Brazil (Rosa 1985a).