This species is distinguished from all its congeners by the following characters: a unique blackish (in live specimens) or dark brown (preserved specimens) general body colouration, which masks the faint vertical bars or a zig-zag pattern of blotches on the flanks; a deeper and posteriorly strongly compressed caudal peduncle, its depth 11.7-14.9 % SL, mean 13% (vs. < 10.9% SL); a deeper body, its depth 17.9-21.6% SL, mean 19.9% (vs. less or equal to 18.3%); stout lower pharyngeal tooth plate bearing molariform teeth on its median area (vs. conical); with maximum size 12.13 cm SL (vs. 8.15 cm SL in the largest known specimen of prionogenys and 8.78 cm SL in wajapi); differs from centrarchus and wajapi by having 3 anal-fin spines (vs. 4); differs from monogramma and centisquama by having the anterior and posterior branches of the lateral line separated by 2 horizontal scale rows (vs. lateral line continuous); differs from gephyrogramma by the absence of a caudal-fin blotch (vs. present, rounded and conspicuous); differs from cinderella by the absence of small dark spots scattered on flanks (vs. presence at least in specimens up to 6.0 cm SL) and by the absence of filamentous dorsal-fin prolongation in sexually dimorphic males (Ref. 108975).