Pseudecheneis stenura, Heok Hee Ng, 2006

Heok Hee Ng, 2006, The identity of Pseudecheneis sulcata (M'Clelland, 1842), with descriptions of two new species of rheophilic catfish (Teleostei: Sisoridae) from Nepal and China., Zootaxa 1254, pp. 45-68 : 57-61

Pseudecheneis stenura sp. nov.

(Fig. 5)

Material examined

Holotype: KIZ 199811999, 132.1 mm SL, China: Yunnan, Baoshan Prefecture, Longchuanjiang at Lianmengjie bridge (Irrawaddy River drainage); C.J. Ferraris, X.-Y. Chen et al., 2- 6 Nov.1998.

Paratypes: CAS 219177 (55), 41.3-180.1 mm SL, data as for holotype.

Diagnosis

Pseudecheneis stenura can be distinguished from congeners in having a longer caudal peduncle (30.3-34.5% SL vs. 20.4-29.0) and, except for P. immaculata , a longer pectoral fin (160.4-196.9% HL vs. 106.9-164.3). It further differs from P. immaculata , P. paviei , P. sulcata , P. sulcatoides , and P. sympelvica in having a prominent bony spur on the anterodorsal surface of the first dorsal-fin pterygiophore (vs. spur absent; Fig. 2) and from P. paviei and P. sympelvica in having more vertebrae (38-40 vs. 33-35) and transverse laminae on the thoracic adhesive apparatus (14-18 vs. 8-12), from P. sympelvica in having the pelvic fins separate (vs. fused at midline) and the sulcae on the thoracic adhesive apparatus continuous (vs. interrupted) across the midline, and from P. sulcata in having a slenderer caudal peduncle (2.9-3.6% SL vs. 4.0-5.2). Pseudecheneis stenura further differs from P. crassicauda in having a slenderer caudal peduncle (2.9-3.6% SL vs. 6.0-6.6) and larger eye (9.2-12.8% HL vs. 7.5-8.3), from P. immaculata in having (vs. lacking) pale colored patches on the body and a shorter adipose-fin base (18.8-23.7% SL vs. 27.7), and from P. serracula in having a shorter adipose-fin base (18.8-23.7% SL vs. 26.8-30.4) and the neural spines of the last 2-3 preanal and first 6-7 postanal vertebrae gradually increasing in height (vs. corresponding neural spines strongly elevated). It can be further distinguished from P. sulcatoides in having a shorter distance between the dorsal and adipose fins (11.5-18.0% SL vs. 19.5-23.1), the first dorsal-fin element present (vs. element absent), the complex vertebra with a bifid neural spine (vs. neural spine not bifid) and the first dorsal-fin pterygiophore with (vs. lacking) a prominent bony spur on the anterodorsal surface, and from P. tchangi in having a slenderer caudal peduncle (2.9-3.6% SL vs. 4.0).

Description

Morphometric data as in Table 3. Head and abdominal region narrow and strongly depressed. Dorsal profile rising gently from tip of snout to origin of dorsal fin, then almost horizontal or sloping very gently ventrally to end of caudal peduncle. Ventral profile horizontal to anal-fin base, then sloping very gently dorsally to end of caudal peduncle. Caudal peduncle long, slender and moderately compressed. Anus and urogenital openings located at posteriormost extent of pelvic fin. Skin smooth, tuberculate in some areas. Lateral line complete and midlateral. Vertebrae 19+18=37 (1), 18+20=38 (7), 19+19=38 (9), 18+21=39* (12), 19+20=39 (18), 20+19=39 (2), 18+22=40 (2), 19+21=40 (2) or 20+20=40 (3).

Head acutely triangular when viewed from above. Gill openings moderate, extending from posttemporal region to base of first pectoral-fin element. Head covered with thick, tuberculate skin. Ventral surface of head with unculiferous collar on distal margin of branchiostegal membrane immediately anterior to thoracic adhesive apparatus.

Thoracic adhesive apparatus consisting of 14-18 transverse ridges (laminae) separated by grooves (sulcae); ridges frequently not meeting at midline of adhesive apparatus. Adhesive apparatus extending from immediately posterior to collar on distal margin of branchiostegal membrane to level of last pectoral-fin ray.

Barbels flattened, and in four pairs. Maxillary barbel with ventral surface densely covered with papillae, and pointed tip; barbel extending about two thirds of distance between its base and base of first pectoral-fin element. Distal half of barbel attached to snout via large, thin flap of skin. Nasal barbel with small flap of thin skin fringing posterior margin and extending midway to distance between posterior nares and anterior orbital margin. Inner mandibular-barbel densely covered with papillae; origin close to midline, extending to collar on distal margin of branchiostegal membrane. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to level of anterior orbital margin. Eye small and almost rounded, subcutaneous and located on dorsal surface of head.

Mouth inferior, with moderately broad, thin papillate lips. Rictal lobe large and papillate. Premaxillary tooth band not exposed when mouth is closed. Premaxillary teeth short and conical, arranged in irregular rows on a moderately large quadrangular patch. Dentary teeth long, thin and somewhat rounded at tip; arranged in irregular rows on two separated, roughly triangular patches.

Dorsal fin origin located at point through anterior third of body. First and second dorsal fin-ray elements not ossified, bearing i,6 (56) rays, and fin margin straight. Adipose fin with short base approximately equal to anal-fin base length; located in middle third of postdorsal region. Fin margin gently convex; posterior end deeply incised. Caudal fin forked, with i,7,8,i (56) principal rays; procurrent rays symmetrical and extend only slightly anterior to fin base. Anal fin with short base extending approximately equal to adipose fin-base length and iii,7 (2), iv,7 (32), iii,8* (14) or iv,8 (8) rays. Fin margin almost straight.

Pelvic-fin origin at vertical through second or third dorsal fin-ray base. Pelvic fin greatly enlarged and with strongly convex anterior margin, first element broadened and with regular striae on ventral surface; with i,5 (56) rays. Pectoral fin greatly enlarged and with convex anterior margin, reaching to just beyond pelvic-fin base. First element not ossified, broadened and with regular striae on ventral surface; fin with i,13 (7), i,14* (43) or i,15 (6) rays.

Coloration

In 70% ethanol: chestnut brown on dorsal and lateral surfaces of head and body, fading to very light brown on ventral region. Dorsal surfaces of head and body with distinctive series of small very light brown spots and bands: one ovate spot on base of first dorsal-fin ray, and another pair on each side of body immediately posterior to last dorsal-fin ray; one band on each side of body at adipose-fin origin, and another on caudal peduncle at base of caudal fin. Dorsal and anal fins hyaline, with brown base and brown subdistal band; brown coloration of base and subdistal band connected to each other at anterior third of fin. Adipose fin light brown, with lighter color around distal edge, especially at posterior end of fin. Caudal fin brown, with hyaline distal margin. Dorsal surfaces of pectoral and pelvic fins brown, ventral surfaces light yellow. Maxillary and nasal barbels brown dorsally and light yellow ventrally.

Distribution

Known from the Longchuanjiang, a tributary of the Irrawaddy River in southwestern China (Fig. 3).

Etymology

From the Greek stenos, meaning narrow, and oura, meaning tail. In reference to the extremely narrow caudal peduncle. Used as a noun.