Systematic revision of the Potamotrygon scobina Garman, 1913 species-complex (Chondrichthyes: Myliobatiformes: Potamotrygonidae), with the description of three new freshwater stingray species from Brazil and comments on their distribution and biogeography Author João Pedro Fontenelle Author Marcelo R. De Carvalho text Zootaxa 2017 4310 1 1 63 journal article 32357 10.11646/zootaxa.4310.1.1 fa2c148d-adf5-4ee3-9eee-d6f18b85c44d 1175-5326 846227 51059A1A-74EE-4DFC-90DD-B9130CE267CB Identification key for species of the Potamotrygon scobina complex 1a. Dorsal disc color with a reticulate, polygonal pattern, lacking ocelli; whitish blotches, when present, very small; tail with dorsal polygonal color pattern at base; dorsal tail thorns at base composed of 2 or 3 irregular rows................. P. limai . 1b. Dorsal color composed of small ocelli, few or numerous, sometimes in combination with whitish small to large blotches; tail without polygonal pattern at base; dorsal tail base with 1 or 2 rows of thorns...................................... 2. 2a. Disc relatively thin and low, head also low, not greatly elevated above disc; tail long and slender, with a well-developed terminal cartilaginous rod; distance between cloaca and tail tip usually greater or equal to disc width...................... 3. 2b. Disc relatively thick and high, head robust and elevated above disc; tail wide and robust, with short cartilaginous rod; distance between cloaca and tail tip smaller than disc width.......................................................... 4. 3a. Dorsal color gray or dark brown; dorsal ocelli usually with accessory whitish blotches; ocelli vary in size, but usually equal or smaller than eye diameter; tooth rows 40/48–50..................................................... P. scobina . 3b. Dorsal color brown to light brown, with evenly distributed ocelli without accessory whitish blotches, and relatively large, usually greater than eye diameter; tooth rows 32–40.................................................... P. garmani . 4a. Dorsal background with small, clearly separated ocellated spots with a darker contour; denticles more concentrated on central disc, disc margins relatively smooth; mean tail length 78.1% DW; tail width at base about 1/5 of disc width; dorsal tail thorns comparatively small........................................................................ P. adamastor . 4b. Dorsal background with numerous whitish spots ocelli fewer and lack a defined black contour; disc totally covered by dermal denticles; tail longer, mean tail length 86.1% DW; tail width at base about 1/6 of disc width; dorsal tail thorns well developed........................................................................................... P. amazona .