Phractura stiassny, 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 : 65-67

Phractura stiassny sp. nov.

(Fig. 12)

Type material. Holotype, AMNH 232265, SL 115 mm, female, Nyanga River, where street crosses river in Tchibanga, Nyanga River system, 03°00'S, 11°00'E, Gabon, col. A. Lamboj, D.Altmann, M.Hasselmann, 24 July 2000.

Diagnosis. A species of Phractura diagnosed by the possession of a well developed pair of neural spines on the first and second post-Weberian vertebrae, that reach the body surface in the space between the supraoccipital process and the nuchal shield of the dorsal fin. Phractura stiassny differs from P. brevicauda in the length of the caudal peduncle (caudal peduncle length 2.6 times in SL vs. 3-4.2 times in SL), in having a pointed snout vs. rounded snout, larger and closer eyes (interorbit separated by one orbit diameter vs. two orbit diameter), longer, more slender barbels (reach beyond branchiostegal border vs. short not reaching near edge of branchiostegal border) and a more slender obscure supraoccipital process vs.broad prominent supraoccipital process in P. brevicauda . This species is similar to P. longicauda and to P. gladysae in having a long slender caudal peduncle but both the latter species have the supraoccipital process and nuchal shield in contact and without intermediate neural spines. P. stiassny has a large Doumea-like head with smooth skin, whereas P. brevicauda and P. longicauda have bony heads with ridges and a relatively shorter snout and smaller more widely separated eyes. P. stiassny is similar in size and some head features to P. gladysae , it differs from the latter in the length of the barbels ( P. stiassny maxillary barbels reach beyond branchiostegal membrane vs.does not reach the edge of the branchiostegal membrane in P. gladysae ). However both species are uncommon and known only from few museum specimens.

Description. Proportional measures and fin ray counts given in Table 9. Body firm, depressed and tapered to a long, slender (depth 28 times in length) caudal peduncle (2.6 times in SL); two pre-dorsal bony scutes, dorsal and ventral bilateral series of thin scutes from adjacent to dorsal fin and behind the pelvic fins respectively, caudal peduncle encased in bony scutes. Head length 5.8 times in SL, head depressed, obtusely pointed, smooth-skinned; snout long, two thirds of head length, nares separated in mid snout; eyes moderately large (orbit 20% HL), narrowly separated by one orbit diameter; mouth subterminal, small, oval shaped, upper lip with small papillae, lower lips smooth, divided by triangular pad; barbels slender, relatively long, papillose, maxillary 0.75 length of head, extends from lateral edge of upper lip, reaching beyond edge of branchiostegal membrane; outer mandibular barbels extend from lateral corner of mouth, reach edge of branchiostegal membrane, inner mandibular barbels on ventral mandible, medial to outer mandibular barbels and separated by medial triangular mandibular pad, not reaching edge of branchiostegal membrane; branchiostegal membrane ventrally undivided, emarginate; supraoccipital process slender, inconspicuous, separated from nuchal shield by space with 2 small bony scutes; humeral process slender, inconspicuous. Fins large, origin of dorsal fin less than one HL behind head; dorsal fin tall, pointed, trailing edge concave; pectoral fins falcate, not reaching pelvic fins, leading ray curved, pectinate, padded; origin of pelvic fins beneath posterior edge of dorsal base, pelvic fins large, falcate, reaching beyond origin of anal fin, leading ray pectinate, padded; anal fin slender, pointed; caudal small, shallow forked; adipose small, behind anal base. Ano-genital pores slightly nearer pelvic bases than origin of anal. Skin smooth, lateral line complete. Reaches 115 mm SL.

Coloration. Greyish-brown above with irregular dark brown and black spots and larger blotches, ventral parts from head to caudal fin cream; head plain grey above; paired fins with sooty band across mid reaches, median fins with distal sooty patches.

Distribution. Known from a single specimen taken from the Nyanga River, Tchibanga, Gabon (Fig. 10).

Etymology. The name ‘ stiassny ’ is used as a noun in apposition. Named for Dr. Melanie Stiassny, Curatrix of Ichthyology at the AMNH in New York, for her contributions to African ichthyology and in appreciation for the support given the author to carry out this study. Dr. Stiassny is the lead editor of the synthesis volume on the fresh and brackish water fishes of the West Central Africa.