Stenorynchoacrum xijiangensis, Huang, Yanfei, Yang, Junxing & Chen, Xiaoyong, 2014

Huang, Yanfei, Yang, Junxing & Chen, Xiaoyong, 2014, Stenorynchoacrum xijiangensis, a new genus and a new species of Labeoninae fish from Guangxi, China (Teleostei: Cyprinidae), Zootaxa 3793 (3), pp. 379-386 : 381-384

Stenorynchoacrum xijiangensis , new species

( Table 1 , Figures 2–4 a)

Holotype. KIZ 2001060488, 78.3 mm SL, Xiangsi Jiang, a tributary of Li Jiang draining to Xi Jiang of Zhu Jiang (Pearl River drainage), Dabu Village, Guilin City, Guangxi Province, China, collected by J. H. Lan on June, 2001 ( Fig. 1 ).

Paratypes: KIZ 2001060482−2001060487, 2001060490−2001060494, 11 specimens, 45.1-83.3 mm SL, same data as the holotype.

Diagnosis. See generic diagnosis.

Description. Morphometric data for 12 type specimens are given in Table 1 . Body elongate and compressed. Dorsal profile of body convex from tip of snout to dorsal-fin origin with the greatest depth, straight from there to caudal-fin base. The ventral profile of body convex from tip of snout to pelvic-fin origin, straight from anal-fin origin to caudal-fin base. Snout rounded and blunt. Snout length almost equal to postorbital length. Mouth gape arched and narrow, its width accounting for 14.1%−22.7% corresponding head length. Nostrils closer to anterior margin of eye than to snout tip. The ventral margin of rostral cap unfringed, completely covering upper lip and the base of upper jaw. Rostral cap connected to lower lip at the corner of mouth. A depression behind rostral barbel base, extending obliquely upward to lateral extremity of snout cap but not meeting with the sublachrymal groove. The lachrymal groove below rostral barbel base extending obliquely down to the corner of mouth and continuous with postlabial groove. The deep postlabial grooves whose length is about 1/3 of corresponding mouth width, divide lower lip into three parts including median portion and two lateral portions. Lateral portions of lower lip free. The median part of lower lip protrudes to form a round fleshy pad, the posterior of which continuous with the mental region. Rostral cap and lower lip covered by regularly arranging, variable fleshy papillae. Among them, two or three rows of papillae at the most-anterior of round fleshy pad smallest, those middle rows of papillae largest.

Papillae on the middle part of rostral cap smaller than those on the sides. Eyes large, dorsolaterally situated in the middle of head, visible from ventral view. Interorbital space wide and flat. Two pairs of barbels, rostral barbels longer than maxillary barbels but shorter than eye diameter, maxillary barbels close to corners of mouth.

Dorsal fin with three simple and 8 branched rays, emarginate; the last unbranched dorsal-fin ray soft and smooth; dorsal-fin origin at midpoint of snout tip and caudal-fin base, and located vertically in front of pelvic-fin origin. Pectoral-fin with one simple and 14 (7) or 15 (5) branched rays, lightly falcate, shorter than head length; tip of depressed pectoral-fin rays extending along 72%−98% of the distance from pectoral-fin origin to pelvic-fin origin. Pelvic-fin with one simple and 8 (12) branched rays, straight, closer to caudal-fin base than to snout tip and closer to anal-fin origin than to pectoral-fin origin; tip of depressed pelvic-fin rays nearly or already reaching anus, its length shorter than head length. Anal-fin with three simple and five branched rays, straight, closer to caudal-fin base than to pelvic-fin origin. Caudal-fin deeply forked, upper and lower lobes almost equal in length and symmetrical in shape, length of the longest ray 1.7−2.4 times length of the shortest median ray.

Lateral line complete and horizontal. Lateral line scales 39 (11) or 38 (1); scale rows above lateral line 6 (12); scale rows below lateral line 4 (12). Predorsal scales irregularly arranged, embedded in small-sized specimens. Scales of abdomen from thorax to base of pectoral-fin small and embedded under skin. Axillary scales at the base of pelvic-fin, scale vagina at dorsal-fin and anal-fin. Circumpeduncle scales 16 (12). Anus located immediately in front of anal-fin origin.

Vertebrae 35 (1), 36 (3), 37 (2). Swimbladder with two chambers: anterior one oval, posterior one elongated, 1.5−2.0 times as long as the anterior one. Gill rakers on first gill arch 8 (1) or 10 (2). Pharyngeal teeth 3 rows, 5, 4, 2−2, 4 and 5. Digestive tract long and coiled, the length is 7.5−8.7 (3) times standard length.

Color pattern in formalin. Preserved in formalin, body gray and yellowish dorsally and laterally, slightly pale ventrally. All fins gray. No stripe or blotches along dorsal and sides of body.

Distribution. Stenorynchoacrum xijiangensis is only known from Xiangsi Jiang, which is a tributary of Li Jiang draining to Xi Jiang of Zhu Jiang Drainage (Pearl River Drainage) in Dabu Village, the south of Guilin City, Guangxi Province, China.

Ecology. The species lives in underground caves connected to the surface river in the Karst area. Fish stay in the underground caves in the dry season and swim upward into the rivers during the flood season.

Etymology. It alludes Xi Jiang, the drainage of the type locality.

Figures

FIGURE 1. The location of Stenorynchoacrum xijiangensis in Guijiang (B), a tributary in Pearl River Drainage of China (A).

FIGURE 2. Diagrammatic of the oromandibular structures in Stenorynchoacrum. Rfp = round fleshy pad of the midian part of lower lip; lj = lower jaw; lpll = lateral part of lower lip; mb = maxillary barbel; pg = postlabial groove; rb = rostral barbel; rc = rostral cap; u j = upper jaw.

FIGURE 3. Lateral view of Stenorynchoacrum xijiangensis, KIZ 2001020488, holotype, 78.3 mm SL.

FIGURE 4. Ventral view of the oromandibular structures in: (a) Stenorynchoacrum xijiangensis, KIZ 2001060488, holotype, 78.3 mm SL; (b) Pseudogyrinocheilus procheilus, KIZ 82101471, 86.0 mm SL; (c) Semilabeo notabilis, KIZ 2006001509, 74.0 mm SL; (d) Parasinilabeo assimilis, KIZ 2002102352, 88.8 mm SL; (e) Rectoris posehensis, KIZ 2001000143, 90.4 mm SL; (f) Ptychidio jordani, KIZ 2008007217, 96.6 mm SL.