Triplophysa pseudostenura, He & Song, 2012

He, Chunlin & Song, Zhaobin, 2012, Triplophysa pseudostenura, a new nemacheiline loach (Cypriniformes: Balitoridae) from the Yalong River of China, Zootaxa 3586, pp. 272-280 : 273-277

Triplophysa pseudostenura sp. nov.

( Figures 1, 2, 3)

Holotype. IHB 20070703001 , male, 120.3 mm SL, Yalong River (tributary of upper Yangtze River drainage), at Gala village (99°58’2.20’’E, 31°37’2.76’’N; 3350 m above sea level), Ganzi County, Ganzi Prefecture, Sichuan Province, China, July 3, 2007, collected by Chunlin He, Peng Cheng and Deqing Tan.

Paratypes. Twenty-nine paratypes. IHB 20070703002–006 , 20070703017–018 , 53.4–103.7 mm SL, paratopotypes ; IHB 820819–20 , 820824 , 820826–28 , 820831 , 820833 , 79.9–140.8 mm SL, Xianshui River (tributary to Yalong River ), Luhuo County, Ganzi Prefecture , August, 1982 ; IHB 820705 , 820707 , 820714 , 820717 , 820724 , 820733 , 83.4–132.1 mm SL, Xianshui River (tributary to Yalong River ), Daofu County, Ganzi Prefecture , July, 1982 ; IHB 821158 , 821203 , 821205 , 821208 , 821214 , 821218 , 821241 , 821249 , 118.0–142.0 mm SL, Yalong River , Dege County, Ganzi Prefecture , June, 1982 .

Diagnosis. Body smooth and without scales; head tapering and relatively narrow (head width 47.6–54.0% HL); eye small (eye diameter 12.1–17.6% HL); lips thin and smooth; trunk slender and laterally compressed; caudal-peduncle length 20.0–23.8% SL; caudal peduncle slender, laterally compressed (cross-section of caudal peduncle elliptic), and tapering, with trunk towards the base of caudal fin; pelvic fin insertion anterior to dorsal-fin origin; dorsal-fin origin closer to caudal-fin base than to snout tip; caudal fin deeply concave; lateral line complete; posterior chamber of gas bladder reduced or absent; intestine short, in zigzag pattern posterior to bottom of ‘U’- shaped stomach (= stomach-like structure sensu Zhu 1989).

Description. Meristic and morphometric characteristics are provided in Table 1. General appearance and characteristics of head, mouth and intestine are provided in Figures 1A, 2A, 2C, 3A, and 3B. Body elongate, smooth and without scales. Anterior portion of trunk very slender and laterally compressed and with a uniform body depth. Posterior trunk without uniform depth but tapering sharply posteriorly towards caudal-fin base, especially along the caudal peduncle. Caudal peduncle slender, laterally compressed and with elliptical-shaped cross-section; caudal peduncle lowest at posterior 2/3 portion. Predorsal body straight; dorsal-fin base and postdorsal profile oblique. Ventral profile of head horizontal; trunk laterally compressed from breast area to caudalfin base; anal-fin base straight; postanal profile slightly concave. Lateral line complete, running along middle of flank.

Head depressed, depth less than width, and nearly triangular in shape when viewed dorsally. Snout acuminate, nearly equal to or slightly less than postorbital head length; interobtial space slightly convex. Eye small and near dorsal profile of head; positioned near midpoint of head. Nostrils closer to anterior margin of eye than to snout tip; anterior and posterior nostrils closely spaced; anterior nostrils smaller than posterior nostrils and pierced at extremity of short tube.

Mouth inferior, horse-shoe shaped. Lips thin; upper lip smooth or slightly furrowed (furrows deepening near corner of mouth) and without median incision. Lower lip with well-marked median incision, slightly furrowed medially and smooth laterally. Upper jaw covered by upper lip; lower jaw scoop-shaped and uncovered medially by lower lip. Barbels in three pairs; inner rostral pair reaching corners of mouth or bases of maxillary barbels; outer rostral pair extending slightly beyond nostrils; maxillary pairs reaching posterior margins of eyes.

Dorsal-fin rays iii/7–8; pectoral-fin rays i/10–12; pelvic-fin rays i/6–7; anal-fin rays ii/5; caudal-fin rays 8–9+8 = 16–17 branched rays. Dorsal fin with truncate distal margin; origin slightly closer to caudal-fin base than to snout tip; posterior end of dorsal-fin base opposite midpoint between pelvic-fin insertion and vent; tip of depressed dorsal-fin rays extending anterior to anal-fin origin. Tip of pectoral fin acuminate, reaching or nearing midway to pelvic-fin insertion. Pelvic-fin insertion midway between snout tip and caudal-fin base, or slightly anterior to dorsal-fin origin; tip of pelvic fin not extending to anus. Anus midway between the tip of pelvic fin and anal-fin origin; distance between anus and anal-fin origin subequal to eye diameter. Distal margin of anal fin truncate or slightly concave, reaching midway to caudal-fin base; anal-fin origin closer to pelvic-fin insertion than to caudalfin base. Caudal fin deeply concave; lower lobe subequal to or slightly longer than the upper; longest branched ray of lower lobe 5/3–4/3 times of median ray.

Gas bladder bipartite; anterior chamber enclosed in dumbbell-like bony capsule and posterior chamber greatly reduced or absent. Intestine short, forming a zigzag loop just below the bottom of the ‘U’-shaped stomach ( Figs. 3A, B), 1.7 times as long as SL.

Sexual dimorphism. Brush-like pads of tubercles present on the heads of males. Males possess a weakly delimited pad of minute, granular tubercles on each side of preorbital region ( Fig. 2A), and have broadened and thickened external (the first 6 or 7) branched pectoral-fin rays, dorsally covered by small, round and condensed epidermal tubercles. In females tip of pectoral fin acuminate and length is subequal to or slightly longer than that of males. Females without tubercles on head and pectoral-fin rays.

Coloration. Trunk and dorsum of living fish gray and venter white. All fins hyaline; anterior part of caudal fin slightly gray. In formalin-preserved specimens, head and body yellowish-brown. Dorsum of body fawn; head, upper half of flank above the lateral line light yellowish; lower half of flank below the lateral line and abdomen flaxen. Upper half of body above lateral line with eight to nine beige transverse bars. Both sides of head and abdomen yellowish, and with no bars or spots present. Dorsal and caudal fins fulvous with some brown spots. Pectoral fins of females flaxen and slightly hyaline; in males pectoral fins fulvous and hyaline along inner distal margin. Pelvic and anal fins flaxen and hyaline; each with dusky basal portion on dorsal surface of outside rays.

Distribution. Occurs in the main stream of Yalong River between Dege and Yajiang counties, and the Xianshui River, a tributary of the Yalong River, between Luhuo and Yajiang counties ( Fig. 4).

Etymology. Derived from Greek “ pseudo ”, alluding to the fact that the species, T. pseudostenura , was first misidentified as Triplophysa stenura .