Pseudexostoma longipterus Zhou & Yang & Li & Li 2007, new species

Pseudexostoma longipterus, new species

(Figs. 2B, 3B, 4, 5)

Material examined. – Holotype: SWFC 200308022, 95.4 mm TL, 82.1 mm SL, Cikai (27 ° 44.27'N 98 ° 40.02"E), Gongshan County, Yunnan Province; W. Zhou, 12 Aug.2003.

Paratypes: SWFC 200308020–021, 200308023–031, 11 ex., 68.2– 113.8 mm TL, 59–99.2 mm SL, same data as holotype.

Diagnosis. – Pseudexostoma longipterus is distinguished from P. yunnanensis by the following combination of characteristics: posterior margin of lower lip with three notches, depth of middle notch shallower than lateral ones (vs. as the same depth), length of two smaller median lobes of lower lip longer than lateral lobes (Fig. 2B) (vs. as the same length, Fig. 2C); pelvic fin i, 3–4 (vs. i, 5); base of adipose fin longer (37.8–45.1% SL vs. 28.8–39.8); caudal peduncle more slender (depth of caudal peduncle 4.6–6.1% SL and 19.6–30.8% in length of caudal peduncle vs. 6.4–8.3 and 32.6–42.7); premaxillary tooth band with 16-18 teeth (vs. 18–22), premaxillary tooth band divided into two and isolated (Fig. 3B) (vs. connected partially, Fig. 3C). Pseudexostoma longipterus differs from P. brachysoma in having a longer pectoral fin, pelvic fin and caudal fin (pectoral fin 30.1–31.3% SL vs. 24.9–29.8, pelvic fin 23.1–24.3% SL vs. 16.1–22.9, caudal fin 18–19.6% SL vs. 13.6–17.9), bigger eyes and wider interorbital width (eye diameter 8.2–10% HL vs. 5.8–7.8, interorbital width 25.5–30.8% HL vs. 19.7–24.7).

Description. – Morphometric data as in Table 1.

Body moderately compressed. Dorsal profile rising evenly and somewhat steeply from tip of snout to origin of dorsal fin, then sloping gently ventrally to end of caudal peduncle. Head and abdominal region before origin of anal fin broad and flat. Body after adipose fin compressed gradually.

Head depressed and broad, triangular when viewed laterally and with rounded snout when viewed from above. Eye small and ovoid, subcutaneous and located at middle of dorsal surface of head. Mouth transverse and inferior, premaxillary and mandibular tooth bands exposed when mouth closed. Teeth embedded in skin, shovel-shaped, tips exposed and arranged in irregular rows. Premaxillary tooth band divided into two, with 16–18 teeth (Fig. 3B). Anterior nostril tubular, separated from posterior nostril by nasal barbel base. Gill opening narrow, extending from one-third of last ray of pectoral fin to the first ray. Dorsal surface smooth without tubercles. Barbels in four pairs. Maxillary barbel flattened, with surrounding flap of skin and rounded tip, extending beyond pectoral fin origin, but not reaching to gill opening and far from post-temporal. Nasal barbel with small flap of thin skin fringing posterior margin and not reaching anterior margin of orbital. Post labial groove connected. Lower lip broad with three notches along posterior margin, divided into two bigger lateral lobes and two smaller median lobes. Depth of middle notch shallower than depth of lateral side notches. Two smaller median lobes of lower lip longer than lateral lobes. Inner mandibular-barbel close to midline, extending to pectoral fin origin. Outer mandibular-barbel precedes lateral inner mandibular barbel, extending to pectoral fin origin (Fig. 2B).

Unbranched dorsal fin rays not ossified. Post-dorsal margin of dorsal fin concave slightly. Origin of dorsal fin located at point through anterior third of body. Adipose fin base not connected with caudal fin. Caudal fin emarginate, upper lobe smaller than lower lobe. Anal fin post-ventral margin emarginate. Distance of anal fin origin to caudal fin base shorter than to end of pelvic fin base. Origin of pelvic fin precedes vertical end of dorsal fin base. Pelvic fin margin convex slightly, not extending to anus. Pectoral fin greatly enlarged and first unbranched ray not ossified. First unbranched ray of paired fins broadened with regular striae on ventral surface. Anus and urogenital openings located at end of pelvic fin and before origin of anal fin. Lateral line midlateral and complete.

Coloration. – Grey black on dorsal surface, no spots or patches. Grey yellow on ventral region. Caudal fin grey black with an irregularly, small, yellow patch in the middle. Fins with grey yellow around distal edge.

Distribution. – Only known from the middle Nujiang basin (Fig. 4).

Etymology. – From the Latin longi-, meaning longer, and the Latin pterus, meaning fin. In reference to the longer pectoral fin, pelvic fin and caudal fin, distinguished from P. brachysoma and P. yunnanensis. A noun in apposition.