Pareuchiloglanis rhabdurus, Heok Hee Ng, 2004

Heok Hee Ng, 2004, Two new glyptosternine catfishes (Teleostei: Sisoridae) from Vietnam and China., Zootaxa 428, pp. 1-12 : 7-10

Pareuchiloglanis rhabdurus sp. nov.

(Fig. 3)

Type material. Holotype: AMNH 211153 , 90.0 mm SL; Vietnam: Ha Giang province, Red River (Song Hong) drainage, Vi Xuyen district, Cao Bo stream (Bac Trao river) near camp 1 , 22°45'18.0"N 104°52'11.4"E; R. C. Schelly et al., 22 April 2000.

Diagnosis. Pareuchiloglanis rhabdurus can be distinguished from the three other species known from Vietnam and adjacent regions in Laos ( P. macrotrema , P. nebulifer and P. poilanei ) in having a more slender body (8.7% SL vs. 9.4-13.6) and caudal peduncle (4.2% SL vs. 5.1-8.6). It further differs from P. macrotrema in having a smaller dorsal to adipose distance (12.2% SL vs. 15.2-20.7), and a longer snout (57.0% HL vs. 50.0-52.1), from P. nebulifer in having a narrower interorbital (25.5% HL vs. 29.3-35.6) and a longer adipose-fin base (34.7% SL vs. 28.3-30.9), caudal peduncle (17.6% SL vs. 13.6-15.7) and snout (57.0% HL vs. 47.8-50.7), and from P. poilanei in having separate (vs. confluent) adipose and caudal fins.

Pareuchiloglanis rhabdurus can be distinguished from all other congeners except P. longicauda and P. sinensis in having the gill opening extending to the base of the first pectoral-fin element (vs. not extending ventrally beyond the third pectoral fin ray). It differs from P. longicauda in having a longer adipose-fin base (34.7% SL vs. 24.5-32.7) and a shorter caudal peduncle (17.6% SL vs. 20.0-22.2), and from P. sinensis in having a more slender body (8.7% SL vs. 14.9-18.6) and caudal peduncle (4.2% SL vs. 8.1-9.3).

Description. Morphometric data as in Table 2. Head and abdominal region moderately broad 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 almost at level of line through posterior pelvic-fin margins. Skin smooth. Lateral line complete and midlateral. Vertebrae 26+14=40.

Head broadly rounded when viewed from above. Gill openings moderate, extending from posttemporal region to base of first pectoral-fin element. Branchiostegal rays 5. Head covered with thick skin. Ventral surface of head and thorax covered with small papillae.

Barbels extremely flattened and in four pairs. Maxillary barbel with thin flap of skin fringing posterior margin and pointed tip; ventral surface with numerous plicae. Barbel extending just beyond base of first pectoral-fin element. Nasal barbel with small flap of thin skin fringing posterior margin and extending to middle of orbit. Inner mandibular barbel origin close to midline, extending to midway between lower lip margin and first pectoral-fin element. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending nearly to first pectoral-fin element. Eye small and almost rounded, subcutaneous and located on dorsal surface of head.

Mouth inferior, with broad, thin papillate lips. Rictal lobe large and papillate. Premaxillary tooth band not exposed when mouth is closed. Oral teeth long, thin and somewhat rounded at tip; in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band broad and of equal width throughout, with a small median indentation on anterior edge. Dentary teeth in two well separated, roughly triangular patches.

Dorsal fin located at point through anterior third of body. Fin without spine, bearing i,6 rays; fin margin straight. Adipose fin with long base extending for about two thirds of postdorsal distance. Fin margin almost straight for entire length (damaged and partially healed, as evidenced by presence of shallow notch); posterior end deeply incised. Caudal fin emarginate, with i,6,6,i principal rays; procurrent rays symmetrical and extend only slightly anterior to fin base.

Anal fin with short base extending approximately one-third of adipose fin-base length and ii,3 rays. Fin margin almost straight. Pelvic-fin origin at vertical through posterior end of dorsal-fin base. Pelvic fin greatly enlarged and with broadly rounded margin, first element broadened and with regular striae on ventral surface; with i,5 rays. Pectoral fin greatly enlarged and with broadly rounded margin, first element broadened and with regular striae on ventral surface; with i,14 rays.

Coloration. Grayish brown on dorsal and lateral surfaces of head and body, light yellow on ventral region. Dorsal surfaces of head and body with series of small light yellow patches: two ovoid patches on occipital region, two on each side of base of first dorsal-fin ray, two on each side of base of last dorsal-fin ray, an elliptical patch on anterior base of adipose fin and another on base of caudal fin. Dorsal fin hyaline, with a grayish brown band on base and middle third of fin. Adipose fin grayish brown, with lighter color around distal margin. Caudal fin grayish brown at base, membranes (but not fin rays) fading to light yellow distally, with dark submarginal band. Anal fin hyaline, with faint gray band on middle one-third of fin rays. Dorsal surfaces of pectoral and pelvic fins grayish brown, ventral surfaces light yellow. Maxillary and nasal barbels grayish brown dorsally and light yellow ventrally.

Distribution. Known from the Song Lo drainage, part of the Red River (Song Hong) drainage, in northern Vietnam.

Etymology. From the Greek rhabdos, meaning rod and oura, meaning tail, in reference to the slender caudal peduncle of this species. Used as an adjective.