Plesiotrygon nana
Plesiotrygon nana, the black-tailed antenna ray, is a species of freshwater stingray in the family Potamotrygonidae. It is native to the western Amazon basin in northeastern Peru, western Brazil, southeastern Colombia, and possibly eastern Ecuador. It is found both in the mainstream of the Amazon and Putumayo Rivers and in smaller tributaries such as the Itaya and Pachitea Rivers. It is occasionally kept in aquariums and has been bred in captivity, but it is sensitive and the tail is easily damaged.
The black-tailed antenna ray is very long-tailed, similar to the only other member of the genus, the long-tailed river stingray. The type specimen, an adult male, had a disc width of, leading to speculations that the black-tailed antenna ray is the smallest member of the family. However, a female kept at the Shedd Aquarium had a disc width of, and later specimens caught in the wild have been up to in width and in weight.