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Comprehensive Description

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Pseudomystus fumosus ZBK sp. nov.

Fig. 6

Type material. Holotype : ZRC 3229, male, 73.6 mm SL; Malaysia : Pahang , Taman Negara, Kuala Tahan; J. R. Hendrickson, July - August 1954 .

Paratype : BIRCUM 4428, 1 male, 66.0 mm SL; Malaysia : Pahang , Sungai Lompat, a tributary of Sungai Krau, 3º41'40"N102º12'40"E ; M. Zakaria-Ismail, 20 Jun 1994 .

Diagnosis. Pseudomystus fumosus ZBK can be distinguished from congeners, except for P. carnosus ZBK and P. moeschii , in having an enlarged and prominent process of the post-temporal(the “supraclavicular process” of previous authors), which is almost as long as (vs. less than one third the length of) the postcleithral process, the presence (vs. absence) of long hair-like epithelial projections on the skin and long tubular extensions of the sensory pores. Pseudomystus fumosus ZBK can be distinguished from both P. carnosus ZBK and P. moeschii in having very well developed procurrent caudal rays that are sinuously curved along the anterior edges (vs. less developed procurrent caudal rays that slope evenly along the edges; Fig. 3). It further differs from P. carnosus ZBK in having a rounded (vs. pointed) tip of the nuchal shield (Fig. 2) and from P. moeschii in having a deeper body (13.0-16.7% SL vs. 13.0-14.5) and lacking (vs. possessing) light colored patches on the body.

Description. Biometric data as in Table 3. Head depressed; dorsal profile slightly convex and ventral profile almost straight; snout broadly rounded when viewed dorsally. Bony elements of dorsal surface of head covered with thin skin; bones visible, especially on posterior half of neurocranium, and ornamented with numerous fine, radial grooves. Midline of cranium with fontanelle extending from behind snout to just beyond level of posterior orbital margin. Supraoccipital process moderately broad, with gently converging sides and blunt tip; extending to nuchal plate. Supratemporal with long posterior process, almost as long as cleithral process. Eye ovoid, horizontal axis longest, with free margin; located entirely in dorsal half of head. Gill openings wide, extending from post-temporal to beyond isthmus. Gill membranes free from isthmus, with 8 (2) branchiostegal rays. First branchial arch with 3+9 (2) gill rakers.

Mouth subterminal. Oral teeth small and viliform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band rounded, of equal width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Vomerine tooth band unpaired, continuous across midline; smoothly arched along anterior margin, tapering laterally to point extending posteriorly past level of premaxillary band; band width narrower than premaxillary band at midline, widening laterally and then tapering to a sharp point postero-laterally.

Barbels in four pairs. Maxillary barbel slender, extending for three quarters of head length. Nasal barbel slender, extending to one third of distance between posterior orbital margin and dorsalmost extent of gill opening. Inner mandibular-barbel origin close to midline, thicker and longer than nasal barbel and extending for half of head length. Outer mandibular barbel originates postero-lateral of inner mandibular barbel, extending for three quarters of head length..

Body slightly compressed, becoming more so toward caudal peduncle. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin and sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile slightly convex to anal-fin base, then sloping slightly dorsally to end of caudal peduncle. Skin smooth, with long hair-like epithelial projections; projections especially prominent on head and dorsal third of body. Lateral line complete and mid-lateral in position, sensory pores of lateral line with long, tubular extensions. Vertebrae 17+23=40 (1)* or 18+24=42 (1).

Dorsal fin with spinelet, spine, and 7 (2) rays. Origin of dorsal fin anterior to midbody, about two-fifths of body. Dorsal fin margin convex, usually with anterior branch of fin rays longer than other branches. Dorsal fin spine short, straight and slender, posterior edge without serrations. Nuchal shield moderately broad, with rounded tip anteriorly.

Pectoral fin with stout spine, sharply pointed at tip, and 7 (1) or 9 (1) rays. Anterior spine margin smooth; posterior spine margin with 15 large serrations along entire length (serrations fewer in smaller specimens). Pectoral fin margin straight anteriorly, convex posteriorly. Cleithral process moderately broad, with slightly convex dorsal margin and extending for two thirds of pectoral-spine length.

Pelvic fin origin at vertical through posterior end of dorsal-fin base, with i,5 (2) rays and slightly convex margin; tip of adpressed fin not reaching anal fin origin. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Males with a conical genital papilla reaching to base of first anal-fin ray.

Adipose fin with convex margin for entire length, with deeply-incised posterior portion and origin in contact with base of last dorsal-fin ray; fin-base long, spanning twothirds of postdorsal distance. Anal fin base just posterior to vertical through origin of adipose fin, with iv,12 (1) or iv,13 (1) rays and curved posterior margin.

Caudal peduncle moderately deep. Caudal fin deeply forked, with i,7,8,i (2) principal rays; upper lobe slender and lanceolate, lower lobe pointed. Procurrent rays extend anterior to fin base, with sinuous anterior margins.

Coloration. In 70% ethanol: dorsal and lateral surfaces of head and body brown, fading to a grayish white on ventral surfaces of head and body. Adipose fin brown. Dorsal, caudal and all paired fins with dusky brown fin rays and hyaline distal margin, inter-radial membranes of all fins with scattered melanophores. Barbels brown dorsally, grayish white ventrally.

Distribution. Known from the upper Pahang River drainage in eastern Peninsular Malaysia (Fig. 4).

Habitat. The holotype of Pseudomystus fumosus ZBK was collected at Kuala Tahan from either the Sungai Tembeling or the Sungai Tahan. The Sungai Tembeling is a large channel over 50 m wide that has cream to reddish sediment-laden water over silt and sand substrates. The Sungai Tahan at Kuala Tahan is a smaller channel that is about 20 m wide with clear but tannin-stained water over rocks, pebble and sand substrate. The paratype was obtained from Kuala Lompat, a tributary of the Sungai Krau. It was caught in a 5-m wide forest stream under 60% canopy cover. The crystal-clear water was about 1 m deep and relatively fast-flowing over a substrate of pebbles and sand (M. Zakaria-Ismail, pers. comm. to second author).

Etymology. From the Latin fumosus, meaning smoke, in reference to its uniform grayish-brown body. An adjective.

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