Mormyrops (Oxymormyrus) boulengeri Pellegrin, 1900
Species overview
Medium-sized fish, body much elongate, low, head pipe-snouted with long, slender, curved snout, very small terminal mouth; blackish brown. Size observed: 247 mm SL.
M. boulengeri(measurements)
Taxonomic description
-Body much elongate, moderately laterally compressed, cross section oval, body depth 11-15 % SL, greatest depth between pelvic and anal fin.
-Head produced into a long, slender, clearly curved* pipe-shaped snout**; head length 29-32 % SL in mature specimens, but strongly dependent on age or size, respectively; head depth 6-10 % SL, 65-85 % body depth.
-Outline of back straight, above pectoral fin slightly concave; upper profile of head convex, upper outline of snout convex, underside of both head and snout concave, outline of belly more or less straight; body may be wavy in outlines.
-Snout long, slender, clearly curved*, 38-50 % head length, 71-108 % postorbital length**.
-Mouth 3-7 % head length, terminal, its edge below posterior nostril, upper jaw on a level with upper edge base of pectoral fin, lower jaw about as deep as upper part of snout.
-Chin with small submental swelling.
-Teeth truncate, very small, in closed lines, 14/14.
-Nostrils separate, circular, very close to end of snout, distance from each other 3-5 % length of snout, distance from eye 85-94 % length of snout; anterior nostril anterior to posterior nostril, their axis inclined about 45 ° to axis of snout.
-Eye diameter 3-5 % head length, 6-8 % postorbital length.
-Opercular cleft curved. 16-25 % head length, 54-77 % head depth.
-Dorsal fin 17 fin-rays, base of D 12-16 % SL, anal fin 38 rays, base of A 26-31 % SL, origin of D well behind origin of A, end of D well before end of A; predorsal length 72-74 % SL, preanal length 63-66 % SL.
-Pectoral fin rounded, its base clearly behind opercular cleft, about half as long as its distance from pelvic fin. V is closer to P than to A.
-Caudal fin rounded, small, the scaled lobes extending to about half of the entire fin. 63-70 scales in lateral line; 8 round caudal peduncle.
-Caudal peduncle 7-9 % SL, its depth 2-4 % SL, 32-48 % its length.
-Coloration »Blackish brown«, in life purplish brown; fin rays black, fin membranes lighter, in the unpaired fins dark at the bases, in particular in the anterior parts.
*) Different from Mormyrops zanclirostris.
**) The extreme shape of the snout changes with age/size of the fish, in juveniles it is much less obvious.
Type locality
»Rivière Alima à Diélé, Congo français« Rep. Congo Brazzaville (Alima 1° 36 ‘ S 16° 36 ‘ E).
Distribution
Middle Congo basin.