Diagnosis: Petrocephalus squalostoma is distinguished from all other Petrocephalus species of the Congo province by the following combination of characteristics: body coloration pattern without intense melanin mark, sometimes a faded subdorsal roundish mark present; short dorsal fin with 15-22 branched rays and 27-32 branched rays in the anal fin; more than 13 scale rows between the anterior base of the anal fin and the lateral line; and three distinct electroreceptive rosettes in the head (Ref. 91772). Body depth 32.9-33.5% of standard length; length of snout to posterior orbital rim of eye 40.9-44.1% of head length; predorsal length 66.7-67.3% of standard length; length of dorsal fin 16.0-17.4% of standard length; preanal length 59.8-60.3% of standard length; distance anterior base of pectoral fin to anterior base of pelvic fin 19.8-20.8% of standard length; caudal peduncle depth 34.6-38.8 of its length (Ref. 91771).

Description: Body asymmetrically oval shape with long, prominent, arched back and deep body; head broadly rounded, with very short snout to posterior orbital rim, 40.9-44.1% of head length; head length 26.3-28.0% of standard length; eye diameter 22.3-25.7% of head length; small mouth ventrally located under the eye; head and body dorsolaterally compressed (Ref. 91771). Teeth small and bicuspid, 5-13 (median 11) teeth in a single row in the upper jaw, 16-23 (median 19) teeth in a single row in the lower jaw (Ref. 91772). Dorsal fin set far back, at about two-thirds of standard length from snout, starting above the fourth or fifth ray of the anal fin; 18-21 dorsal fin rays (Ref. 91771). Predorsal length 66.7-67.3% and preanal length 59.9-60.3% of standard length (Ref. 91771). Anal fin length 24.1-25.0% of standard length, longer than and opposite dorsal fin; 29-31 anal fin rays (Ref. 91771). Slender, subcylindrical caudal peduncle, with depth 34.6-38.8% of its length; its length 18.4-19.2% of standard length (Ref. 91771). Scales extending anteriorly to operculum and pectoral fins; 39-42 scales on lateral line; 12 circumpeduncular scales (Ref. 42540, 91771).

Colour: homogeneously brown in preservation (Ref. 91771). Body background mostly silver-white/gold with metallic reflections, darker dorsally from the snout to the caudal peduncle (Ref. 91772). In a few specimens presence of a pale subdorsal roundish mark lying below the anterior base of the dorsal fin, on each side of the body (Ref. 91772). All fins whitish-yellowish, mostly translucent with fine black pigmentation on the lepidotrichia (Ref. 91772).