Petrocephalus sauvagii is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics: very wide mouth (mouthwidth 2,7 to 3,7 in head length) associated with a characteristic head shape when viewed from above, anal fin with at least 32 branched rays, dorsal fin with at least 25 branched rays, mouth subterminal, ration between the head length and the mouth position as large as 7,4 (Ref. 85331). It has 17-30 teeth in upper jaw, and 29-35 teeth in lower jaw (Ref. 2915, 85331). Pigmentation pattern with two melanin markings, sometimes of weak intensity or even scarcely visible: (1) an irregularly round black mark below the anterior base (first to fourth rays) of the dorsal fin; and (2) an ovoid blackish mark, often irregularly shaped, at the base of the caudal fin, extending onto the upper and lower fleshy lobes of the fin (Ref. 85331).