Diagnosis: Nannocharax signifer is distinguished from all other Nannocharax species in West Africa by the red-orange colouration of the anterior part of its dorsal fin (Ref. 85591). The combination of the following characters is also diagnostic: no continuous black band along the flank; multiple x-shaped body colour pattern extending on the lower half of the flank; 46-48 lateral line scales; and 4-5 scales between anus and origin of anal fin (Ref. 85591).

Description: Body shape typical for Nannocharax: elongated with a slender body, oval in cross section, only slightly laterally compressed; body depth greatest directly in front of dorsal fin (Ref. 85591). Head pointed, mouth small and subterminal; eye slightly closer to tip of snout than to end of head; eye diameter about one third of head length (Ref. 85591). Body completely covered with ctenoid scales; lateral line complete, straight along body, with 46 to 48, usually 47 scales; 4.5 scale rows between lateral line and origin of dorsal fin and 4.5 scale rows between lateral line and origin of pelvic fin; 14 scale rows around caudal peduncle (Ref. 85591). Dorsal fin at about middle of body, with 3-4 simple rays of which 1-2 are supernumerary; dorsal-fin origin at vertical through pelvic-fin origin or slightly behind; caudal fin deeply bifurcate with equal lobes; 9 dorsal procurrent rays, 10 upper principal rays, 9 lower principal rays and 8 ventral procurrent rays; pectoral fin with 14-16 rays, usually 14; tip of pectoral fin behind origin of pelvic fin; pelvic fins well separated from each other, with 9 rays; anal fin with 10-11 rays, usually 10 (Ref. 85591). Usually 38 vertebrae in total, rarely 39; 19 abdominal and 19 caudal vertebrae (Ref. 85591).

Colouration: In alcohol body pale brownish or yellowish, without difference between upper and lower half of the body; prominent pattern on body: 8-9 dark brown saddle-like blotches along mid-dorsal line; blotches usually reaching 2-3 scale rows down flank; first four blotches scarcely vary among the specimens: first saddle-like blotch close to head, second ending at dorsal-fin origin, third at middle of dorsal fin and fourth starting behind dorsal-fin base; along horizontal septum 6-7 black slightly rectangular blotches; additionally irregular pattern of X-shaped marks along flank, mainly concentrated on lateral line scale row and two rows below; lower part of head white, upper part light brown with dark areas in occipital region and on opercle; black stripe from eye to snout; pectoral fin transparent with slight brownish stripe in distal third; pelvic-fin transparent with one brown stripe about in middle; brown marks on anterior part and base of anal-fin not always present; a conspicuous black spot on anterior extremity of anal-fin base commonly present; caudal fin with much pronounced dark-brown blotch at base of lower lobe; additional dark marks at about one-third and two-third of fin length, less pronounced on median rays; adipose fin transparent; dorsal-fin membrane transparent; first rays with 2 to 3 black marks on all rays, appearing as black bands; most distal blotches on anterior rays sometimes much pronounced, probably sex-dependant (Ref. 85591). In life, first rays of dorsal fin conspicuously red or red-orange; belly reflecting white; back and upper half of flanks light brown or olive; pattern identical to preserved specimens (Ref. 85591).