Oreoglanis macronemus, Ng, 2004

Ng, Heok Hee, 2004, Oreoglanis Macronemus, A New Species Of Glyptosternine Catfish (Teleostei: Siluriformes: Sisoridae) From Northern Laos, Raffles Bulletin of Zoology 52 (1), pp. 209-213 : 209-211

Oreoglanis macronemus , new species

( Fig. 1 )

Material examined. – Holotype – BMNH 1933.8 .19.51, male, 64.7 mm SL, Laos: Xieng Khouang, coll. J. Delacour & W. Lowe, 1926.

Paratypes – BMNH 1933.8.19.52–54, 2 ex., females, 47.5–59.7 mm SL , 1 ex., male, 61.8 mm SL, data as for holotype .

Diagnosis. – Oreoglanis macronemus shares with members of the O. delacouri group a lower lip lacking a median notch,

with prominent projections along the posterior margin and a lunate caudal fin with extended principal rays. This distinguishes it from congeners of the O. siamensis species group ( O. insignis , O. macropterus , O. setiger and O. siamensis ), which have a median notch on the lower lip, with an entire or weakly laciniate posterior margin, and emarginate caudal fins. It can be distinguished from congeners of the O. delacouri species group in having a shorter caudal peduncle (15.6–17.3% SL vs. 18.7–27.1) and longer nasal barbels (35.4–41.7% HL vs. 11.2–32.0). It is further distinguished from O. delacouri , O. infulatus , O. hypsiurus and O. lepturus in having a deeper caudal peduncle (4.2–4.9% SL vs. 2.1– 3.6), and from O. frenatus in having more vertebrae (39–40 vs. 36–38).

Description. – Morphometric data as in Table 1. Head moderately broad and extremely depressed; dorsal profile slightly convex and ventral profile almost straight. Eye ovoid, horizontal axis longest, subcutaneous; located dorsally on head. Gill openings extremely narrow, extending from middle of pectoral-fin base to level just medial to base of last pectoralfin ray.

Mouth strongly inferior, with broad, thin and papillate lips. Lower lip lacking median notch, posterior margin with lobulate projections. Postlabial groove on lower jaw present and uninterrupted. Jaw teeth pointed and in large, broad band with small median indentation and rounded ends on both sides in upper jaws. Two kinds of teeth present on lower jaw in two separate, roughly triangular patches: anterior teeth short and spatulate, with curved inner face; posterior teeth pointed as in those of upper jaw.

Barbels in four pairs. Maxillary barbels flattened, with membranous flap of skin on dorsoposterior edge and rounded tip. Ventral surface with numerous plicae, with crenulate ventroposterior edge. Nasal barbel extending to point midway between barbel base and anterior orbital margin. Inner mandibular-barbel origin close to midline immediately under lower lip and extending to imaginary line through bases of the first pectoral-fin elements. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to base of first pectoral-fin element.

Body extremely depressed, becoming compressed towards caudal peduncle. Dorsal profile rising very gently from tip of snout to origin of dorsal fin, then almost horizontal to end of adipose fin base, sloping gently ventrally thereafter to end of caudal peduncle. Ventral profile horizontal to anus and thereafter sloping dorsally to end of caudal peduncle.

Skin smooth. Lateral line complete and midlateral in position. Vertebrae 24+15=39 (n=1), 25+14=39 (n=1), 26+13=39 (n=1) or 26+14=40 (n=1).

Dorsal fin with first element not ossified and i,6 (n=4) rays; fin margin convex. Pectoral fin greatly enlarged, with first element thickened but not ossified, and i,15,i (n=2) or i,17 (n=2) rays. Ventral surface of thickened first pectoral-fin element with numerous striae. Pectoral-fin margin strongly convex. Pelvic-fin origin at midpoint of body. Pelvic fin enlarged, with i,5 (n=4) rays and convex margin. Ventral surface of first pelvic-fin element with numerous striae. Anus and urogenital openings located at vertical through line through posterior quarter of adpressed pelvic fin. Anal fin with short base and ii,4 (n=4) rays. Caudal peduncle short. Caudal fin lunate, with i,5,5,i (n=3), i,6,5,i (n=4) or i,6,6,i (n=1) principal rays.

Males with small conical genital papilla immediately posterior to anus in depression terminating posteriorly with straight transverse wall. Females with tube-shaped papilla similarly positioned.

Colour. – In 70% ethanol: brown on dorsal and lateral surfaces of the head and body, dark yellow on ventral region. A paler, dark yellow ovoid patch on the dorsum at the base of the first dorsal-fin element present. Dorsal and caudal fins brown; dorsal surfaces of pectoral and pelvic fins brown, with light yellow ventral surfaces. Anal fin yellow. Dorsal surface of barbels brown, ventral surface light yellow. Caudal-fin base with a vertical darker band that extends along outermost lower principal caudal rays.

Etymology. – From the Greek makros, meaning long, and nema, meaning thread. In reference to the long nasal barbels of this species. Used as a noun in apposition.

Distribution. – Known from the Xieng Khouang region, most likely from either the Nam Ngiap or the Nam Sen drainage (see discussion).

Figures

Fig. 1. Oreoglanis macronemus, new species, BMNH 1933.8.19.52, paratype male, 61.5 mm SL; Laos: Xieng Khouang.