Pseudecheneis crassicauda, Heok Hee Ng & David R. Edds, 2005

Heok Hee Ng & David R. Edds, 2005, Two new species of Pseudecheneis, rheophilic catfishes (Teleostei: Sisoridae) from Nepal., Zootaxa 1047, pp. 1-19 : 2-5

Pseudecheneis crassicauda sp. nov.

(Fig. 1)

Pseudecheneis sulcatus (non M’Clelland, 1842) Shrestha, 1981: 197, Fig. 91 (in part); 1994: 62, Fig. 97 (in part).

Type material. Holotype: BMNH 1958.9.1.8, 103.7 mm SL; Nepal: Mewa Khola (River), Dhankuta District, 27°0'N 87°20'E; J. C. Getley, date unknown.

Paratypes: BMNH 1958.9.1.9 (1), 56.8 mm SL; data as for holotype. BMNH 1970.12.14.230 (1), 136.8 mm SL; Nepal: Mewa Khola (River), Sanghu; K. Hyatt, 7 December 1961.

Diagnosis. Pseudecheneis crassicauda is distinguished from P. paviei and P. sympelvica in having an elongate body with 38-39 vertebrae (vs. short body with 33-35 vertebrae) and from P. sympelvica in having separate (vs. fused) pelvic fins. It differs from other congeners in having a deeper caudal peduncle (6.0-6.6% SL vs. 3.8-5.5) and (except for P. immaculata ) a smaller eye (7.5-8.3% HL vs. 8.8-12.8). It further differs from P. immaculata in having a shorter adipose-fin base (1.5-2.0 times of anal-fin base vs. more than 2.0; 20.3-24.3% SL vs. 27.7) and the presence (vs. absence) of pale spots on the body, and from P. sulcata in having pelvic fins that reach (vs. do not reach) the base of the first anal-fin ray.

Description. Morphometric data as in Table 1. 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 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+19=38 (1), 19+20=39* (1) or 20+19=39 (1).

Head acutely rounded 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 12-15 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 (3) rays, and fin margin straight. Adipose fin with short base, approximately 1.5 to 2 times of anal-fin base length; located in middle third of postdorsal region. Adipose fin margin gently convex; posterior end deeply incised. Caudal fin forked, with i,7,7,i (2) or i,7,8,i* (1) 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 iv,6 (1), v,7 (1) or v,8* (1) rays. Anal fin margin almost straight.

Pelvic-fin origin at vertical through second or third dorsal fin-ray base. Pelvic fin greatly enlarged, extending to base of first anal-fin ray. Anterior fin margin strongly convex, first element broadened and with regular striae on ventral surface; with i,5 (3) 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,12 (1) or i,13* (2) 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 surface 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 dorsalfin 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 Mewa Khola (River), which is part of the Tamur River drainage (Fig. 2). The Tamur River is an eastern tributary of the Kosi River, Nepal’s largest river, which flows through eastern Nepal and into the Ganges River in India.

Etymology. From the Latin crassus, meaning thick, and cauda, meaning tail, in reference to the deep caudal peduncle of this species. Used as an adjective.