Diagnosis: Petrocephalus odzalaensis is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics: dorsal fin shorter than anal fin; dorsal fin with a maximum of 22 branched rays; anal fin with a minimum of 27 branched rays; mouth sub-terminal, ratio between head length and mouth position is between 4,2 and 5,0; and eye small, the ratio head length and eye-diameter between 3,7 and 4,2 (Ref. 85331). Body pinkish-gray, darker dorsally, with the presence of three distinct pigmentation patches: (1) a distinct ovoid black mark situated below the anterior base of the dorsal fin on each side of the body; (2) a small black mark at the base of each pectoral fin; (3) an ovoid black mark on each side that is centered at the base of the caudal fin, not extending onto the upper and lower lobes of this fin (Ref. 85331).
Description: Body ovoid, longer than high, the ratio standard length and height between 2.6 and 2.9, and laterally compressed (Ref. 85331). Head length between 3.7 and 4.0 times in standard length (Ref. 85331). Snout short, the ratio head length and snout length between 6.2 and 8.3, and round (Ref. 85331). Mouth small, the ration head length and mouth width between 4.0 and 4.8, subterminal, opening just under the anterior half of the eye (Ref. 85331). Teeth small and bicuspid, 8-12 in a single row in the upper jaw, 18-23 in a single row in the lower jaw (Ref. 85331). Caudal peduncle thin, the ration caudal peduncle length and caudal peduncle depth between 1,9 and 2,3 (Ref. 85331). Dorsal and anal fins originate in the posterior half of the body; pre-dorsal distance slightly greater than the pre-anal distance; dorsal fin with 20-22 branched rays; anal fin with 27-29 branched rays (Ref. 85331). Scales cover the body, except for the head; lateral line visible and complete with 36-38 pored scales along its length; 10-14 scales between the anterior base of the anal fin and the lateral line; 12 scales around the caudal peduncle (Ref. 85331). Skin on head thick, turning opaque with formalin fixation; knollenorgans clustered into three distinct rosettes (Ref. 85331).
Colouration: Body background colour pinkish-gray, darker dorsally; pigmentation pattern consisting of three characteristic black patches: a distinct ovoid black mark below the anterior base of the dorsal fin; a small black mark at the base of the pectoral fin; and an ovoid black mark centered at the base of the caudal fin, which does not extend onto the upper and lower lobes; fins translucent (Ref. 85331).