The dwarf freshwater stingray commonly known as the Black tailed antenna ray in the aquarium trade has finally been formally named in a recent issue of the journal PapÃ©is Avulsos de Zoologia.
Marcelo Carvalho and Maíra Ragno name the new stingray from the upper and middle Amazon River drainage Plesiotrygon nana, after its small adult size (Latin nanus=dwarf).
Plesiotrygon nana differs from its only congener, P. iwamae, in a number of ways, including having the dorsal surface of the disc with highly convoluted yellowish lines or small spots composed into very fine rosettes or a combination of spots and irregular ocelli, a circular disc, a broadly rounded snout, very small and less rhomboidal spiracles, a short snout and a narrow mouth and nostrils.
In addition, the denticles on the dorsal surface of the tail are small, scattered, and not forming a row of enlarged spines, it has significantly fewer tooth rows in adult and preadult fish, fewer caudal vertebrae, and a higher number of pectoral radials.
This species also has a very small adult size, probably not surpassing 25cm/10" disc length or width.
For more information, see the paper: de Carvalho, MR and MP Ragno (2011) An unusual, dwarf new species of Neotropical freshwater stingray, Plesiotrygon nana sp. nov., from the upper and mid Amazon basin: the second species of Plesiotrygon (Chondrichthyes: Potamotrygonidae). Papéis Avulsos de Zoologia 51, pp. 101–138.