Diagnosis: Within the Congo basin, Distichodus langi can be distinguished from D. affinis, D. altus, D. decemmaculatus, D. noboli, D. notospilus and D. teugelsi by its higher total number of lateral line scales, 68-70 vs. less than 46; from D. maculatus by the absence of large, dark spots all over the body and a higher number of dorsal fin rays, 26-28 vs. 19-21; from D. antonii by its inferior, vs. terminal, mouth, its higher number of scales between the lateral line and the dorsal fin, 15-16 vs. 10-12, and its higher number of lateral line scales in front of the hypural joint, 68-70 vs. 52-64; from D. fasciolatus by its higher number of dorsal fin rays, 26-28 vs. 24-26, its higher number of pelvic fin rays, 11 vs. generally 10, and its deeper head, 67.4-69.4% of head length vs. 35.9-62.9% of head length; from D. lusosso by its inferior, vs. terminal, mouth and feebly compressed snout, vs. distinctive prolonged; from D. sexfasciatus by its feebly compressed snout, vs. strongly compressed, its higher number of dark vertical bars along the body, 13 vs. 6-7, and its higher number of teeth on the outer row on both jaws, more than 20 vs. 12-14; and from the D. atroventralis complex by a higher number of scales between the lateral line and pelvic fin, 12 vs. 9-11, its higher number of pectoral fin rays, 21 vs. 17-20, its higher number of circumpeduncular scales, 24-25 vs. 20-24, and its deeper head, 67.4-69.4% of head length vs. 35.1-55.7% of head length (Ref. 96324).

Description: Body relatively deep; dorsal head profile and dorsal body outline concave to end of dorsal fin, straight from end of dorsal to adipose fin, and convex from adipose to caudal fin; ventral head profile straight, concave from posterior to head to end of anal fin, and convex from end of anal to caudal fin (Ref. 96324). Head compressed with nasal openings relatively closely set, 14.4-15.9% of head length, but deep, 67.4-69.4% of head length; mouth inferior; posterior edge of maxillary not passing the nostrils; two rows of bicuspid teeth in each jaw (Ref. 96324, 122092). Origin of dorsal fin well in front of pelvic fin origin along vertical axis; distal margin dorsal fin straight or slightly concave, distal margin of anal fin straight to slightly convex; base and distal end of pelvic fin relatively close to vent, 23.4-25.9% of standard length and 1.6-7.8% of standard length respectively; pectoral and pelvic fin rays decreasing in length from outer to inner fin margin; adipose fin little further removed from dorsal fin than from caudal fin; caudal peduncle deeper then long; caudal fin forked with two rounded lobes covered with numerous small scales except for translucent area distally (Ref. 96324).

Colouration: The body of the two preserved specimens is uniformly brown-yellowish, with a slightly lighter belly; dorsal fin scattered with many small, dark spots; caudal fin brownish, with slightly darker median rays; adipose fin with translucent distal margin; pectoral fins pale to yellow-orange; pelvic fins generally pale, sometimes the distal edges are darker coloured; thirteen vague dark vertical bars have been observed on the flanks of the additional specimen, whereas the holotype has none (Ref. 96324).