Potamotrygon is a genus of freshwater stingrays in the family Potamotrygonidae, a group of rays that abandoned the sea entirely and now live out their whole life cycle in South American rivers; the atlas records species across Brazil, Argentina, Paraguay, Venezuela, Bolivia, Colombia, Peru, and Suriname. Like other stingrays they have a flattened, disc-shaped body with the mouth and gill slits on the underside and eyes on top, and they retain one or more venomous, barbed spines near the base of the tail for defense — a real hazard keepers and waders both need to respect. Unlike marine rays, Potamotrygon give birth to live young nourished in the uterus rather than laying eggs. The atlas covers 32 species with disc sizes from about 8–37.5 in, and many carry bold spot, blotch, or net-like patterning that makes the genus one of the most visually striking freshwater fish groups.
Species such as the Ocellate River Stingray (Potamotrygon motoro), the Black-Diamond Stingray (P. leopoldi), and the Tiger River Stingray (P. tigrina) are prized centerpiece fish in the specialist ray-keeping side of the hobby, valued for their patterning and genuinely unusual biology rather than typical community-tank behavior. They are a demanding, expert-level group: large aquaria, a soft sand substrate to protect the delicate underside, and meticulous water quality are all needed, and most aquarium specimens today are captive-bred given that several source countries restrict export of wild-caught individuals. The conservation picture is one of the more concerning in the atlas: the IUCN tally shows a substantial share of species rated Vulnerable, Near Threatened, or Endangered, driven by habitat loss, damming, and historically heavy collection pressure for the aquarium trade itself.