Schistura altuscauda, Chen & Myint & Chu & Chen, 2020

Chen, Meng-Fang, Myint, Khin Mar, Chu, Ling & Chen, Xiao-Yong, 2020, Two new species of loaches from the Irrawaddy River basin, Chin State, Myanmar (Teleostei: Cypriniformes: Nemacheilidae), Zootaxa 4895 (1), pp. 86-102 : 95-99

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Schistura altuscauda

sp. nov.

Schistura altuscauda sp. nov.

( Fig. 10 View FIGURE 10 )

Holotype. KIZ 2018002400 View Materials , 64.8 mm SL. Myanmar: Chin State: Mindat Town: Htin stream, 22°21’31”N, 94°4’28”E, 441 m elevation, Paing Zaw , Nay Htet Naing , 27 March 2018. GoogleMaps

Paratypes. KIZ 2018002401–2403 View Materials , SEABRI 20181223, 26–30, 20181234, 48.4–73.0 mm SL; 10 specimens; same data as holotype GoogleMaps .

Diagnosis. Schistura altuscauda sp. nov. can be distinguished from all other species in the area by a combination of the following characters: high caudal peduncle (14.0–20.3% SL), strong processus dentiformis on upper jaw; 7–19 bars on flank of body, bars in front of dorsal fin obviously thinner than those behind, sometimes fused in front of dorsal fin; lateral line complete; males with prominent suborbital flap; and pelvic lobe present.

Description. General appearance and morphometric data of holotype and paratypes are shown in Fig. 10 View FIGURE 10 and Table 2, respectively.

Body moderately thick, slightly increasing from nape to dorsal fins, gradually decreasing from dorsal-fin base to caudal-fin base. In lateral view, head short, eyes large, small concavity between head and body. Head with swollen cheeks, snout round, nasal valve triangular in dorsal and lateral view. Caudal peduncle depth 1.1–2.3 times its length. Developed axillary pelvic lobe. Largest known size 73.0 mm.

Dorsal fin with 3 simple and 7½–8½ branched rays, distal margin slightly concave, origin anterior to pelvic-fin origin. Pectoral fin with 1 unbranched and 9–10 branched rays, reaching half distance to base of pelvic fin. Pelvic fin with 1 unbranched and 6–7 branched rays, origin between first and second branched dorsal rays, not reaching anus, which lies approximately 1.5 eye diameter in front of anal-fin origin. Anal fin with 3 simple and 5½ branched rays, not reaching caudal-fin base. Caudal fin lunate, with 9+8 branched rays.

Body almost completely covered by scales, except on thorax and abdomen. Lateral line complete, 85–92 pores. Cephalic lateral line system with 8 supraorbital, 4+10 infraorbital, 10 preoperculo-mandibular, and 3 supratemporal pores.

Anterior nostril pierced on anterior side of pointed flap-like tube, forming tip and low anterior rim. Mouth shallowly arched ( Fig. 11 View FIGURE 11 ). Upper lip with small incision, 11–12 deep furrows on each side. Lower lip with median interruption, 3–4 deep furrows in median area. Processus dentiformis present, wide and strong. Lower jaw exposed, without median notch. Interior rostral barbel reaching half distance to base of maxillary barbel; exterior rostral barbel reaching mouth corner. Maxillary barbel reaching vertical of posterior margin of eye. Intestine with large loop some distance behind stomach ( Fig. 12 View FIGURE 12 ). Gill rakers 15–15 (1).

Sexual dimorphism. Males possess large triangular downward suborbital flap ( Fig. 13 View FIGURE 13 ).

Coloration (preserved in formalin). Ground color in preserved specimens pale yellowish gray. Head with

vermicular pattern on top, snout, suborbital area, and opercle. Irregular bar pattern from nape to dorsal-fin origin. 7–19 black brown bars on body, bars in front of dorsal fin obviously thinner than those behind, sometimes fused together in front of dorsal fin and wider than interspaces. 3–4 saddles from dorsal-fin base to caudal fin-base. Bars from dorsal fin-base to caudal peduncle-base meet on other side of body. Dorsal fin hyaline, with three rows of black spots. 3 black spots at dorsal midline, located at base of first unbranched ray and branched ray, third branched ray, and 4 th– 6 th branched rays, respectively. Caudal fin hyaline, with 4 rows of black spots; in paratypes, without black spots ( Fig. 14 View FIGURE 14 ). Others fins hyaline.

Distribution. Schistura altuscauda sp. nov. is presently only known from the type locality, Irrawaddy River basin in Htin stream, Mindat Town, Chin State, Myanmar ( Fig. 8 View FIGURE 8 ).

Etymology. The name is from the Latin altus (= high) and cauda (= caudal), referring to the presence of a high caudal peduncle.