Common names
Smooth back river stingray

Short Description
Diagnosis after DA SILVA & DE CARVALHO, 2015 [22907]: A species of Potamotrygon from the Amazon basin distinguished from congeners by the following combination of characters: dark brown dorsally, with slender dorsal reticulate pattern delimiting rounded, fragmented spaces composed of small dark beige spots with diameter smaller than eyes; dorsal tail with lateral black stripes; ventral tail medially white, with gray margins; distal tail dark gray with vermiculate white spots randomly distributed; disc thick at pectoral bases; spiracles small, their aperture equivalent to one and a half times eye length; clearly demarcated labial ridges at lower jaw corners; small triangular monocuspidate teeth in males and trapezoidal and tricuspidate teeth in females; dorsal tail spines usually in a single irregular row; lateral tail spines developed and distributed from tail-base to region posterior to caudal sting origin; submarginal tubercles rare and isolated. Potamotrygon humerosa can be distinguished from P. orbignyi by its dorsal coloration composed exclusively of broad rounded fragmented spaces within slender reticulations (vs. reticulate pattern usually delimiting hexagonal spaces, or reticulation surrounding circular, ringed or rosette-like markings), smaller tail length (means 82% vs. 92% DW, respectively), tail with conspicuous lateral spines from base to origin of caudal sting (lacking in P. orbignyi); lower number of total (means 119.4 vs. 125.5, respectively) and diplospondylic vertebrae (84.5 vs. 91.5, respectively), and a smaller size at maturity (means 255.3 mm DW in males and 268.7 mm DW in females vs. 346.2 mm DW in males and 363.2 mm DW in females in P. orbignyi). Potamotrygon humerosa can be distinguished from P. marinae by lacking vivid, wide and rounded orange blotches and spots within reticulations on dorsal disc, by its mostly white ventral disc color (vs. mostly dark gray in P. marinae), by having a greater branchial basket length (means 18.3% vs. 16.9% DW, respectively), and by its lower number of mesopterygial radials (means 15.4 vs. 18, respectively).

Distribution
Occurs in the Amazon River, and in lower reaches of the effluents Canumã, Negro, Abacaxis, Trombetas, Tapajós, and Pará, but appears to be absent from the Tocantins-Araguaia basin [22907]

Biology
freshwater

Size / Weight / Age
DW (male): 90–332 mm (n=13); (female) 90–311 mm (n=27) [22907]

Remarks
shark-references Species-ID=7967; CITES: (see: Protected Species for more details) Convention on International Trade in Endangered Speciesof Wild Fauna and Flora annex: III; Council Regulation 2017/160 annex: C

Parasites (arranged by Jürgen Pollerspöck)
Monogenea

• Potamotrygonocotyle chisholmae Domingues & Marques, 2007 [14308]
• Potamotrygonocotyle dromedarius Domingues & Marques, 2007 [22565]
• Potamotrygonocotyle rionegrense Domingues, Pancera & Marques, 2007 [14549]
• Potamotrygonocotyle tsalickisi Mayes, Brooks & Thorson, 1981 [14308] [14549] [22565]