This species is distinguished from its congeners, except N. yapo, by having enlarged odontodes on distinct swollen skin along snout lateral margins in mature males (vs. absent); it differs from N. yapo by having enlarged odontodes along ridges before the eyes in mature males (vs absent); differs further from N. corumba and N. yapo by having a greater mandibullary width/HL, 19.9-21.8 (vs. 16.3-18.1 and 14.1-15.2, respectively), and greater caudal peduncle depth/SL, 6.7-7.7 (vs. 6.0-6.5 and 6.0-6.3, respectively); differs from N. paranensis by having a well-developed adipose fin (vs. reduced or absent), and greater orbital diameter/HL, 12.1-12.7 (vs. 7.9-12.0); from N. franciscoensis and N. ribeirensis by having well-developed dorsal-fin spinelet, wider than dorsal-fin spine base (vs. absent or narrower than dorsal-fin spine base); from N. granosus by having 28-30 (vs. 34-43) lateral line plates and greater orbital diameter/HL. 12.1-12.7 (vs. 9.0-11.0); from N. microps by having a greater orbital diameter/HL, 12.1-12.7 (vs. 8.0-11.0), and 15-24 (vs. 5-12) dentary teeth; from N. variipictus by having a smaller snout length/HL, 57.4-65.0 (vs. 66.7-72.0), greater orbital diameter/HL, 12.1-12.7 (vs. 9.1-9.9), 17-24 (vs. 12-14) premaxillary teeth, and 15-24 (vs. 7) dentary teeth (Ref. 75575).

Description: The body is relatively short and depressed, ventrally flattened to anal-fin origin, flattened to slightly rounded to caudal fin; greatest body depth is at dorsal-fin origin.Profile of dorsal body gently convex, elevating from snout tip to dorsal-fin origin and descending to first caudal-fin procurrent spine; dorsal body surface is completely covered by dermal plates, except for a naked area around dorsal-fin base; snout tip is naked; ventral head surface is naked except by a plate bearing odontodes in front of gill openings; abdomen with conspicuous, small dermal platelets between insertions of pectoral and pelvic fins, forming a thoracic shield surrounded by naked areas; the head is wide and moderately depressed, with head and snout rounded in dorsal view in larger specimens, and slightly obtuse in smaller ones; snout gently convex in lateral profile; mature males with moderately hypertrophied odontodes and swollen skin along lateral margins of snout sides, head anterior portion, and along ridge in front of eye; moderately small eye, dorsolaterally placed; well developed and rounded lips with the lower lip relatively small, not reaching pectoral girdle and covered by papillae, wider anteriorly; one or two irregular and conspicuous rows of large and transversally flattened papillae, just posterior to dentary teeth; the maxillary barbel is short and coalesced with lower lip, generally with free tip; teeth long, slender and bicuspid; the mesial cusp longer than lateral; dorsal-fin spinelet is half-moon shaped and wider than dorsal-fin spine base; the dorsal-fin with spine flexible; adipose fin moderate to well developed, generally preceded by 1 or 2 (rarely) azygous plates; pectoral fin with a depressed and inward curved spine (more curved in larger specimens), shorter than longest branched ray; pelvic-fin spine ventrally flattened, the dermal flap on its dorsal surface in males; caudal fin bifurcate with the lower lobe longer than upper and with 14 branched rays; pectoral and pelvic-fin spines with odontodes in lateral and ventral portions while anal-fin spine with odontodes only ventrally (Ref. 75575).