Diagnosis: distance from tip of snout to last externally visible dorsal spine 49.5-67.6% SL (mean 60.5%), decreasing with size; postanal length 38.5-53.4% SL (mean 44.7%), increasing with size; distance from tip of snout to last externally visible anal spine 49.2-67.0% SL (mean 59.1%), decreasing with size; distance from posterior edge of pectoral fin to anterior origin of first dorsal spine, 19.4-86.4% HL (mean 52.4%); gill opening small, its distance to dorsal pectoral fin base relatively long, 8.3-14.9% HL (mean 11.5%); 24+1 up to 33+1 (median 30+1) dorsal spines; origin of soft dorsal fin slightly anterior or posterior to origin of soft anal fin (Ref. 81678).
Description: 0-4 preopercular spines (loss of spines with increasing size); 0-1 preorbital spine (loss of spine with increasing size); anterior origin of first dorsal spine always clearly situated posterior to posterior edge of pectoral fin; preanal length relatively long, 44.9-61.0% SL (mean 53.8%), decreasing with size; preanal length longer than postanal in small-sized specimens gradually becoming of equal size with increasing size; preanal length even shorter than postanal in largest examined specimens; distance from anterior border of snout to last externally visible dorsal spine largely comparable to (often somewhat larger than) distance from anterior border of snout to last externally visible anal spine (Ref. 81678). Intraspecific variation: (1) with increasing size the preanal length decreases proportionally to the increase of the postanal length; (2) the preorbital spine, if present, has a tendency to disappear with size; in small specimens, the presence/absence of a preorbital spine may vary according to the basin of origin; (3) preopercular spines, if present, have a tendency to decrease in number with size; the number of preopercular spines may vary considerably between specimens of the same basin; (4) the number of dorsal spines shows an important amount of geographical variation (Ref. 81678).
Coloration: In preservation: overall colour uniformly brown; upper sides and dorsal mid-line lighter brown with a series of small dark brown spots on dorsal mid-line, extending along dorsal, caudal and anal fin bases; generally a dark brown band originating at base of rostral appendage and continuing posteriorly along sides of body and tail; upper edge of lateral band with a well delimited battlement-like pattern and lower edge ill defined; some specimens with more uniformly coloured dark brown sides; ventral side of head, belly, and abdomen lighter brown or whitish with virtually no markings; exceptionally, a dark brown netting around pectoral fin region; general colour of dorsal, caudal and anal fins whitish; dorsal fin with an additional series or a somewhat more irregularly displaced sequence of small dark brown spots; anal fin also with such an additional series, sometimes with a few additional dark brown spots situated on posterior half of fin; caudal fin with a single, or in some specimens two, large dark brown spot(s); pectoral fins whitish with no or sometimes a few, dark brown spots; unpaired fins darker in larger specimens; Congo River basin specimens generally with a more developed netting pattern surrounding large yellowish white spots on the lower flanks (Ref. 81678).