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Diagnosis: Petrocephalus pulsivertens is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics: dorsal fin with at least 25 branched rays; anal fin with at least 31 branched rays; mouth large, the ratio head length and mouth width between 2.0 and 3.7; 15-21 teeth in the upper jaw; 24-30 teeth in the lower jaw; and eye large, the ratio head length and eye-diameter between 3,2 and 3,5 (Ref. 85331). Pigmentation pattern consists of two distinctive melanin markings (black patches): (1) a distinct ovoid mark below the anterior base of the dorsal fin; and (2) a crescent-like mark, sometimes diffuse, centered at the base of the caudal fin and extending onto the upper and lower parts of the caudal 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 3.6 and 3.7 times in standard length (Ref. 85331). Eye large, the ration head length and eye-diameter between 3.2 and 3.5 (Ref. 85331). Snout short, the ratio head length and snout length between 6.1 and 7.3, and round (Ref. 85331). Mouth large, the ratio head length and mouth width between 3.0 and 3.7, subterminal, opening just under the anterior half of the eye (Ref. 85331). Teeth bicuspid, small and numerous, 15-21 in a single row in the upper jaw, 24-30 in a single row in the lower jaw (Ref. 85331). Caudal peduncle relatively thin, the ratio caudal peduncle length and caudal peduncle depth between 2.1 and 2.3 (Ref. 85331). Dorsal and anal fins originate in the posterior half of the body; pre-dorsal distance equal to, or slightly greater than, pre-anal distance; dorsal fin with 25-27 branched rays; anal fin with 31-35 branched rays (Ref. 85331). Scales cover the body, except for the head; lateral line visible and complete with 38-40 pored scales along its length; 13-15 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, becoming opaque with formalin fixation; knollenorgan electroreceptors on head clustered into three distinct rosettes (Ref. 85331).
Colouration: Body and head mostly whitish-silvery, but head also exhibits faint metallic blue-purple iridescence; dorsum darker than the rest of the body; melanin patterning consists of two distinct black marks: a distinct ovoid melanin mark below the anterior base of the dorsal fin on each side of the body and a crescent-like melanin mark, sometimes diffuse, centered at the base of the caudal fin on each side and extending onto the upper and lower parts of the caudal fin; no black mark is present at the base of the pectoral fins; the fins themselves are mostly translucent, with the dorsal and caudal fins sometimes turning slightly yellow after formaldehyde preservation (Ref. 85331). |