Petrocephalus tenuicauda (Steindachner, 1895)
Species overview
Small fish, body moderately short and deep, head about as long as deep or slightly shorter, snout short, mouth inferior. Head with three aggregations, »rosettes«, of cutaneous sensory organs. Brown, purplish-brown speckled, anterior rays of dorsal fin purplish-black. Size observed: 117 mm SL.
P. tenuicauda(measurements)
Taxonomic description
-Body moderately short, strongly laterally compressed, body depth 27-38 % SL, greatest depth at between pelvic and anal fin.
-Head length 23-27 % SL; head depth 22-30 % SL, 76-86 % body depth.
-Outline of body from origin of dorsal to origin of anal fin parabolic, upper profile of head convex, underside of head convex. Bases of unpaired fins steeply running to caudal peduncle.
-Snout short, 12-21 % head length, 19-35 % postorbital length, upper jaw on a level with lower edge base of pectoral fin.
-Mouth width 27-28 % head length, inferior, its edge below posterior rim of lens.
-Chin inconspicuous.
-Teeth notched, 6-13/16-24.
-Nostrils closely together, upright-oblong, on a level with lower rim of lens, posterior nostril very close to rim of eye; axis parallel to axis of head.
-Eye large, diameter 22-31 % head length, 33-48 % postorbital length. Three rosettes, aggregations of electrorecpetors, on the head.
-Opercular cleft strongly curved, 41-48 % head length, 33-56 % head depth.
-Dorsal fin 24-29 fin-rays, base of D 19-25 % SL, anal fin 30-35 rays, base of A 23-29 % SL, origin of D well behind origin of A, end of D before end of A; predorsal length 58-62 % SL, preanal length 53-59 % SL.
-Pectoral fin pointed, extending to middle of pelvic fin or slightly beyond. V is distinctly closer to P than to A.
-Caudal fin pointed, scaled part obtusely pointed, short. 39-42 scales in lateral line; 12 round caudal peduncle.
-Caudal peduncle 19-22% SL, its depth 4-8 % SL, 18-35 % its length.
-Coloration »Head purplish-brown, trunk brown with silvery shine and densely speckled with purplish-brown dots«. (Steindachner) »A large almost purplish-black, nearly triangular spot on the anterior part of the dorsal fin, from the base of the 8-11th rays to the tips of the 3-4th rays, without being distinctly marked off posteriorly«. (Bigorne and Paugy)
Type locality
»?aus dem Du Queah- und Junk-Flusse« Liberia.
Distribution
Atlantic slopes of Guinea, Sierra Leone and Liberia.
Electric organ discharges
P. tenuicauda(elec. organ)