Amphilius caudosignatus, 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 : 48-50

Amphilius caudosignatus sp. nov.

(Fig. 4)

Type material. Holotype, CU 86631, SL 35.5 mm, Kiené Creek, Motoboi Village, 01°32'S, 13°32'E, upper Ogowe River system, Gabon, col. J.P. Sullivan, M.E. Arnegard, C.D.Hopkins, 12 August 1999 ; 3 paratypes: 1, CU 90864, SL 29 mm, same data as holotype ; 1, CU 80784, SL 36.1 mm, Forest stream near Omoy village, tributary of Lékay River, 01°46’S, 13°46’E, upper Ogowe River system, Gabon, col. CD. Hopkins, M.E. Arnegard, J.B. Heiser, J. Beck, J.P. Sullivan, 7 August 1999 ; 1, CU 82334, SL 49.6 mm, Mimboumbou Creek, near Franceville, 13°8’17”S, 13°31’12”E, upper Ogowe River system, Gabon, col. J.P Sullivan et al., 5 August 1999 .

Diagnosis. A small species of Amphilius with 6+7 principal caudal fin rays and an unique coloration consisting of a distinct caudal fin colour pattern, which is dark brown with a white base and a broad oblique white band from mid-dorsal to post-ventral corner. This species appears to be confined to a narrow range in the Ogowe basin, and is most similar to A. nigricaudatus Pellegrin , which is widespread in the WCA region including the Ogowe River system. In addition to colour pattern it differs from A. pulcher and A. dimonika in the forward position of the eyes, i.e. its eyes are nearer the tip of the snout than the hind end of the head and vice versa in the latter species. It differs from A. korupi in having a more slender caudal peduncle (136-175% CPL/CPD vs.90-138% CPL/CPD) and A. korupi is a larger species. However, A. caudosignatus may reach a larger size than available material indicates and so its small size may not necessary be characteristic. It has fewer caudal vertebrae than A. nigricaudatus (17-18 vs. 19-21) and hence fewer total vertebrae (31-32 vs. 32-34). Its distinctive caudal fin colour pattern is similar to another undescribed species collected from the Odzala National Park in the Republic of Congo (Brazzaville) (John Friel, personal communication). That species however also has a different, distinctive colour pattern on the body.

Description. Proportional measurements and fin ray counts are given in Table 2. Body relatively short, slender, depressed anteriorly, width tapering to compressed caudal peduncle. Head smooth above, short, broad, and depressed with blunt (obtuse) anterior profile, head length 3.8-4.3 times in SL, branchiostegal membrane deeply cleft mid-ventrally; mouth sub-terminal, broad; lips thin; teeth numerous, small and caniniform on a square premaxillary pad and in a narrow band on anterior mandible; barbels filamentous, maxillary longest, extending from lateral end of upper lips and reaching to above base of pectoral fins; mandibular barbels reach to edge of branchiostegal membrane, anterior pair on ventral mandible lateral to symphysis, posterior pair on ventral mandible postero-lateral to anterior pair; snout shorter than post-orbit distance; nares in mid-snout, separated; eyes small, widely spaced (interorbit 2.8-3.3 times orbit diameter) positioned near middle of head, orbits without free border. Fins moderately large, origin of dorsal less than one head length behind head, ahead of origin of pelvic fins; dorsal base to above origin of pelvic fins; dorsal hind margin straight; pectoral fins rounded, leading ray slender, pectinate and padded, not reaching pelvic fins; pelvic fins rounded, leading ray slender, pectinate, padded, not reaching anal; anal short based and slender, not reaching caudal; caudal fin slender and emarginate or shallow forked, base with dark, semi-oval epidermal fold; adipose fin long, extending from behind pelvic base to procurrent ridge of caudal fin, gently curved. Skin smooth; lateral line with well spaced pores, complete, along mid-line to caudal base. Anus close to base of pelvic fins. Size reached 49.6 mm SL.

Coloration. Dorsal and lateral surfaces dark brown, with scattered darker spots over head and body dorsum becoming less dense behind and below; a lighter, whitish saddle patch behind dorsal base, ventral surface before anal fin light cream, brown pigment extends across ano-genital region. Base of fin rays brown, membranes clear. Caudal fin distinctive with basal third and postero-dorsal lobe dark brown or black, separated by a oblique creamy white band extending from mid-dorsal to distal ventral lobe. The larger paratype (CU 82334) does not have a whitish saddle behind the dorsal base.

Distribution. South-eastern tributaries of the Ogowe River, Gabon (Fig. 3).

Etymology. Caudo -meaning tail, signatus -meaning striking, refers to the distinctive caudal colour pattern.