Amphilius dimonikensis, Paul H. Skelton, 2007

Paul H. Skelton, 2007, New species of the amphiliid catfish genera Amphilius, Doumea and Phractura and the taxonomy of Paramphilius from West Central Africa (Siluriformes, Amphiliidae)., Zootaxa 1578, pp. 41-68 : 44-45

Amphilius dimonikensis sp. nov.

(Fig. 2)

Synonymy. Amphilius pulcher , non Pellegrin; Mamonekene & Teugels 1993, 44-45.

Type Material. Holotype, MRAC 92-125-P-324, SL 55.6 mm, Mpoulou River, Kouilou River system, at confluence with Kibouba above the Divenda rapids, Republic of Congo, 04° 02' S, 12° 21 ' E, V Mamonekene, 9 July 1992 ; 5 paratypes: 1, SAIAB 79509 (ex MRAC 92-125-P-325), SL 43.5 mm male, same data as holotype ; 2, MRAC 92-125-P-326-327, SL 26.6 mm, 34.2 mm, not sexed, Mpoulou River, tributary of Kouilou River, at confluence of Kiada, Republic of Congo, 04°02' S, \2°2Y E, V.Mamonekene, 9 August 1992 ; 2, MRAC 92-125-P-328-329, SL, 21 mm, Kiadi River, tributary of Mpoulou, Kouilou River system, at the confluence, Republic of Congo, 04°02' S, 12°21' E, V. Mamonekene, 9 August 1992 .

Diagnosis. A combination of characters separate this species from other Amphilius . It is one of several Amphilius characterized by 6+7 principal caudal rays. This character separates it from several species with 8+9 rays found in East and southern Africa (Skelton 1984) and from A. longirostris (with 7+8 principal caudal rays) in the WCA. The position of the eyes is slightly closer the hind margin of the head than the tip of the snout, similar to A. pulcher but a feature that distinguishes it from other species in the region with 6+7 caudal rays. In the WCA A. dimonikensis is most similar to A. pulcher , from which it differs most markedly in colour pattern (a regular pattern of brown bands and lighter saddles versus an irregular pattern of striking dark brown or black patches for the latter), as well as in the size of the adipose fin (adipose length = 21% SL vs. 34 % in A. pulcher ). A. dimonikensis has fewer vertebrae (31-32 total vertebrae vs. 33-34) particularly fewer caudal vertebrae (17-18 vs.19-20) than A. pulcher . It differs in pigment pattern from the species described below as Amphilius caudosignatus , Amphilius korupi , Amphilius mamonekenensis as well as from Amphilius nigricaudatus .

Description. Measurements and fin ray counts given in Table 1. Body stout, depressed anteriorly, width tapering to a compressed caudal peduncle. Head length 3.5-3.9 times in SL. Head depressed and rounded anteriorly; branchiostegal membrane deeply cleft mid-ventrally; mouth broad, subterminal, lips thick and fleshy; premaxillary teeth caniniform in a medially broad and laterally tapered band and mandibular teeth caniniform in a narrow band; 3 pairs of filamentous barbels, maxillary barbels subequal to head length extending from the upper lips; mandibular barbels on ventral surface of mandible, inner positioned latero-medially behind anterior edge of jaw, outer mandibular pair postero-lateral to inner pair; snout moderately long, half of head length, nares in mid-snout, narrowly separated; eyes about midway or slightly nearer hind margin of head, moderate sized, closely spaced (interorbit 1.2 to 1.9 times orbit diameter), confluent with head (orbital margins attached). Caudal peduncle short (5.9-7.1 times in SL), slightly longer than deep (length 1.2-1.5 times depth). Fins well developed, dorsal base entirely in advance of pelvic fins, origin less than one head length behind head, rectangular with leading simple ray equal to length of leading edge; pectoral fins not reaching pelvic fins, rounded with leading ray curved, padded and pectinate, innermost (posterior) rays align against lateral body wall; pelvic fins broad, with padded pectinate leading ray, not reaching base of anal; anal fin short, not reaching base of caudal; caudal fin with simple epidermal fold over base of rays, hind edge emarginate, ventral lobe slightly longer than dorsal lobe; adipose fin well developed, rounded, base extends from before origin of anal to base of caudal procurrent ridge. Skin smooth, lateral line complete along midline to base of caudal fin. Anus positioned about one third of distance from base of pelvic fins to origin of anal fin. Size reached 55.6 mm SL.

Coloration. Head and body dark brown with 4-5 light (creamish) saddle bands on dorsal surface, and a light (off-white) ventral surface from head to anal fin. Fins with brown rays; caudal fin with broad basal dark brown band and a distal dark brown band.

Distribution. Known only from the Mpoulou River, a tributary of the Kouilou River within the Dimonika Biosphere Reserve, Mayombe, Republic of Congo (Fig. 3).

Etymology. The name ‘dimonikensis’ refers to the Dimonika Biosphere Reserve, Mayombe, Republic of Congo, from where this species is likely to be endemic.