This species is distinguished by the following characters of which the first three are unique among the Pimelodidae and the last is unique among the Brachyplatystomatini: jaw teeth dimorphic with mostly fine, densely spaced outer teeth and relatively few (3-6) inner rows of slender, straight, inwardly depressible teeth; juveniles (< 200 mm SL, but some as large as 300 mm SL) marked by bold, large (twice or more times eye diameter) dark brown or gray spots centered above lateral line; ground color in preservative tan to medium brown; adults and juveniles (> ca. 200 mm SL) black to very dark gray or brown dorsally and abruptly countershaded along a horizontal from snout tip to caudal-fin base, especially along posterior half of body just above or at lateral line; ventrally it is plain white to dusky cream; most specimens with light patch anterior to upper lobe of caudal fin; caudal fin of adults is moderately to shallowly forked, lobes broad and nearly equal (Ref. 55106).