Pareuchiloglanis prolixdorsalis, Xu Li, Wei Zhou, Alfred W. Thomson, Qing Zhang & Ying Yang, 2007

Xu Li, Wei Zhou, Alfred W. Thomson, Qing Zhang & Ying Yang, 2007, A review of the genus Pareuchiloglanis (Sisoridae) from the Lancangjiang (upper Mekong River) with descriptions of two new species from Yunnan, China., Zootaxa 1440, pp. 1-19 : 15-17

Pareuchiloglanis prolixdorsalis sp. nov.

(Fig. 8)

Holotype. SWFC 0105002 , 161 mm TL, 146 mm SL; Xiaonuoyou (22°14’04”N 100°36’75”E), Nabanhe (small branch of Lancangjiang) , Jinghong County, Yunnan Province, L.-X. Hang, 2 May 2001.

Paratypes. SWFC 0105001, 0105003-0105005 (4; 135-170 mm TL, 120-148 mm SL), same data as holotype. SWFC 0303249 (1; 92.8 mm TL, 80.4 mm SL), Donggualin (24°18.43’N 100°46.61’E), Xiaobahe (upstream of Weiyuanjiang, a branch of Lancangjiang) , Zhenyuan County, Yunnan Province, W. Zhou & Q. Wang, 29 Sept. 2003.

Diagnosis. Characters distinguishing Pareuchiloglanis prolixdorsalis from P. abbreviatus , P. gracilicaudata , P. kamengensis and P. myzostoma are summarized in Table 1. A species of Pareuchiloglanis with the following unique combination of characters: adipose-fin base not confluent with caudal fin (vs. confluent); premaxillary tooth patches appear joined (vs. separate); lower lip connected to base of maxillary barbel by skin flap, without sulcus between them (vs. not connected, with sulcus); 6 upper + 7 lower branched caudalfin rays (vs. 7+8); dorsal fin i-5-6 (vs. i-7); anal fin ii-4 (vs. ii-8); distance between pelvic-fin origin to anal-fin origin longer than distance between pelvic-fin origin to mouth (vs. equal); pectoral fins not reaching origin of pelvic fin (vs. reaching); origin of pelvic fins opposite to end of dorsal-fin base (vs. posterior to end of dorsalfin base); anus nearer to posterior end of pelvic-fin base than to anal-fin origin (vs. nearer to anal-fin origin); long interdorsal, tip of dorsal fin not reaching origin of adipose fin when depressed (vs. reaching); caudal peduncle length 18.2-22.2% SL; caudal peduncle depth 4.5-5.6% SL.

Pareuchiloglanis prolixdorsalis is distinguished from P. gongshanensis , P. feae , P. kamengensis and P. macropterus by the following characters: premaxillary tooth patches appear joined with a median indentation (vs. separate) (Fig. 2A); lower lip connected to base of maxillary barbel by skin flap, and without sulcus between them (vs. not connected, with sulcus) (Fig. 3A). It differs from P. abbreviatus and P. anteanalis by its shorter pectoral fin, pectoral fin not reaching origin of pelvic fin (vs. reaching). It differs from P. feae , P. poilanei , P. sichuanensis and P. tianquanensis by adipose-fin base not being confluent with caudal fin (vs. confluent). It differs from P. abbreviatus by having tip of dorsal fin not reaching origin of adipose fin when depressed (vs. reaching). It differs from P. gracilicaudata , P. myzostoma , P. nebulifer and P. robusta by having 6+7 branched caudal-fin rays (vs. 7+8). Pareuchiloglanis prolixdorsalis differs from P. songdaensis by having distance between pelvic-fin origin to anal-fin origin longer than distance between pelvic-fin origin to mouth (vs. equal). It differs from P. songmaensis by having fewer fin rays, dorsal fin i-5-6, anal fin ii-4 (vs. i-7, ii-8).

Pareuchiloglanis prolixdorsalis differs from P. sichuanensis and P. sinensis by narrower caudal peduncle, depth 4.5-5.6% SL (vs. 7.8-11.4% SL). It differs from P. rhabdurus by its longer and deeper caudal peduncle, length 18.2-22.2% SL (vs. 17.6% SL) and depth 4.5-5.6% SL (vs. 4.2% SL). It further differs from P. gongshanensis , P. kamengensis , P. macropterus and P. myzostoma by having the origin of the anus nearer the posterior end of the pelvic-fin base (vs. nearer anal-fin origin).

Description. Morphometric and meristic data are in Table 3. Mouth wide, inferior, transverse. Anterior margin of premaxillary tooth patches exposed when mouth closed. Oral region with papillae. Oral teeth coniform, embedded in skin, only tips exposed, irregular rows. Premaxillary tooth patches broad, appear joined, with median indentation, sides not extending backwards (Fig. 2A). Gill opening extending from posttemporal region to base of second pectoral-fin element. Post-labial groove interrupted, ending at base of inner mandibular barbel. Lower lip connected to base of maxillary barbel by skin flap, without sulcus between them (Fig. 3A).

Head compressed, rostral margin rounded when viewed dorsally. Head and abdominal region moderately broad. Dorsal profile rising gradually from tip of snout to origin of dorsal fin, then sloping slowly ventrally to end of caudal peduncle. Oral region, anterior part of abdomen with dense papillae, density gradually decreasing posteriorly. Eye small, almost round, subcutaneous, dorsal. Eye closer to tip of snout than to dorsalmost extremity of gill opening. Barbels flattened, in four pairs. Nasal barbel with small flap of thin skin fringing posterior margin, reaching anterior orbital margin. Maxillary barbel with thin flap of skin fringing posterior margin, pointed tip, extending to or beyond pectoral-fin origin. Origin of inner mandibular barbel close to midline. Outer mandibular barbel origin posterolateral of inner mandibular barbel, reaching nearly to first pectoral-fin element.

Dorsal fin at point through anterior third of body; without spine, margin straight, extending beyond vertical through base of pelvic fin. Tip of dorsal fin not reaching origin of adipose fin when depressed. Adipose fin with long base, third of postdorsal distance, fin margin almost straight for entire length, adipose-fin base deeply incised posteriorly. Length of adipose-fin base equal to predorsal length. Origin of anal fin posterior, inserted nearer to caudal-fin base than to end of pelvic-fin base. Pectoral and pelvic fins enlarged, with broadly rounded margins, first element on each broadened, with regular striae on ventral surface. Pectoral fin not reaching origin of pelvic fin. Pelvic fin reaching anus. Anus located nearer to posterior end of pelvic-fin base than to anal-fin origin. Caudal fin truncate. Skin smooth. Lateral line complete and midlateral.

Colouration. Green yellow on dorsal surface, milk-white on ventral region. Light yellow spot on posttemporal area. Pair of yellow spots on dorsal, adipose, caudal fins. Pectoral and pelvic fins green-yellow with lighter colour around distal edge. Dorsal fin green-yellow with lighter medial band and distal edge. Caudal fin gray-black with small yellow patch in middle.

Distribution. Lower reaches of the Lancangjiang [Mekong] drainage (Fig. 4).

Etymology. From the Latin prolixus, meaning extended, and dorsalis, meaning dorsal. In reference to the longer distance from the end of the dorsal-fin base to the origin of the adipose-fin, distinguished from P. abbreviatus in the same river system.