Growing to a disc diameter of about 1.9 m (6.2 ft) and a weight of 220 kg (490 lb), with unconfirmed records of even larger specimens,[4] the short-tailed river stingray is the largest freshwater species in its family[3] and one of the heaviest strict freshwater fish in South America, only matched by the arapaima (Arapaima) and piraíba catfish (Brachyplatystoma filamentosum).

[7] The ray's tail is very muscular and thick, covered with short spines at the base and a venomous sting at the end.

[5] In the north it ranges from the upper Paraguay River basin, including the Pantanal, and south to the lowermost freshwater sections of the Río de la Plata.

[5] Unlike some other freshwater rays, it has not been able to spread to the upper Paraná River basin after the Itaipu Dam flooded the Guaíra Falls, which represented a natural barrier to its range.

[1][6] The pups start off eating plankton and then move on to consume small mollusks, crustaceans, the larvae of aquatic insects, and fish.