Glyptothorax rugimentum, Ng & Kottelat, 2008

Ng, Heok Hee & Kottelat, Maurice, 2008, Glyptothorax Rugimentum, A New Species Of Catfish From Myanmar And Western Thailand (Teleostei: Sisoridae), Raffles Bulletin of Zoology 56 (1), pp. 129-134 : 129-132

Glyptothorax rugimentum , new species

( Fig. 1 )

Material examined. – Holotype – ZRC 50572, 78.6 mm SL, Myanmar: Kayin State, Ataran River drainage, stream “Chon Son” between Kyondaw and Phadaw, about 20 km NW of Payathouzu (at border with Thailand), 15º25'N 98º15'E; coll. K. Kubota, Dec.2002.

Paratypes – CMK 17784, 5 ex., 64.5–75.6 mm SL, data as for holotype . CMK 17950, 1 ex., 70.0 mm SL, same data as holotype, Mar.2003 . UMMZ 247301 , 12 ex., 43.0– 53.7 mm SL, Myanmar: Ataran River drainage; K. Udomritthiruj, 2006 . CMK 16243, 3 ex., 55.5–58.5 mm SL, Thailand: Mae Hong Son, Salween River drainage, Nam Mae Sariang at dam SW of Amphoe Mae Sariang; M. Kottelat et al., 8 Apr.2000 . UMMZ 246033 , 1 alc., 1 c&s, 60.5– 68.9 mm SL, Thailand: Salween River drainage; K. Udomritthiruj, 2005 . ZRC 50843, 2 ex., 65.6–70.5 mm SL, Thailand: Tak, Salween River drainage, Mae Lamao ; Y. Y. Goh & Y.-X. Cai, 9 Jun.1998 . UMMZ 245971 , 2 ex., 44.5–49.7 mm SL, Myanmar: Bago, Sittang River drainage, Pyu township, Pyu stream ca. 229 km from Yangon, 18 ° 29'N 96 ° 26'E; Than Kyaw Toe, Sep.2005 .

Diagnosis. – Glyptothorax rugimentum , new species, can be distinguished from all congeners except G. indicus in having the unculiferous ridges of the thoracic adhesive apparatus extending anteriorly onto the gular region (vs. gular region without unculiferous ridges). It can be distinguished from G. indicus in having a wider head (19.1–22.6% SL vs. 16.3– 18.9), larger eye (8.4–11.6% HL vs. 6.2–8.1), shorter nasal barbels (not reaching anterior orbital margin vs. reaching to middle of orbit; 24.5–37.1% HL vs. 37.8–52.5), a narrower thoracic adhesive apparatus (in a rhomboidal, somewhat Ushaped field vs. a more laterally divergent chevron-shaped field), pelvic-fin origin at (vs. posterior to) vertical through base of last dorsal-fin ray, a more steeply-sloping posterior margin of the adipose fin, and the presence (vs. absence) of light and dark vertical bands on the caudal peduncle.

Description. – Biometric data in Table 1. Head depressed, body subcylindrical. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally from anal-fin base to end of caudal peduncle. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin tuberculate, with small tubercles on sides of body. Lateral line complete and midlateral. Vertebrae 15+20=35 (2), 16+19=35 (5), 17+18=35 (1), 16+20=36 (8), 17+19=36 (3), 16+21=37 (1), 17+20=37 (5) or 17+21=38 (1).

Head depressed and broad, triangular when viewed laterally. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill openings broad, extending from immediately ventral to post-temporal to isthmus. Bony elements of dorsal surface of head covered with thick, tuberculate skin. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel long and slender, extending to middle of pectoral-fin base. Nasal barbel slender, extending to three-quarters of distance between its base and anterior orbital margin. Inner mandibular-barbel origin close to midline, extending to midway between its base and that of pectoral spine. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to threequarters of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band partially exposed when mouth is closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth in single broad semilunate band. Dentary teeth in two narrow crescentic bands separated at midline.

THE RAFFLES BULLETIN OF ZOOLOGY 2008

Dorsal fin located above anterior third of body, with I,6 (26) rays; fin margin convex; spine short and gently curved. Adipose fin with anterior margin straight or very slightly concave and posterior margin angular. Caudal fin strongly forked, with lower lobe very slightly longer than upper lobe and i,7,7,i (26) principal rays. Procurrent rays symmetrical and extending only slightly anterior to fin base. Anal-fin base ventral to adipose-fin origin. Anal fin with straight anterior margin and straight or slightly concave posterior margin; with iii,7 (22) or iv,7 (4) rays. Pelvic-fin origin at vertical through posterior end of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (26) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,8 (22) or I,8,i (4) rays; posterior fin margin slightly concave; anterior spine margin smooth, posterior margin with 10–12 serrations.

Thoracic adhesive apparatus present, consisting of ridges of skin in rhomboidal field and forming a somewhat U-shaped appearance with depressed area. A median depression present on posterior half and extending from isthmus to level of middle of pectoral fin. Median ridges orientated longitudinally, lateral ones radiating from median depression. Ridges uninterrupted except for posteriormost lateral ridge, which are dissociated into irregular small, unculiferous patches. Median longitudinal ridges extending anteriorly along ventral midline of body to cover gular region.

Colouration. – In 70% ethanol: Dorsal and lateral surfaces of head, and body brown to brownish grey, fading to beige on ventral surfaces. A diffuse, dark brown saddle-shaped blotch on dorsal and lateral surfaces of body immediately behind head. A series of vertical bars on body and caudal peduncle (bars are diffuse and indistinct in some individuals): a dark bar running through anterior bases of adipose and anal fins and on body in between; a pale bar running through posterior bases of adipose and anal fins; a dark bar running through middle third of caudal peduncle; a pale bar running through posterior third of caudal peduncle; a dark bar running through caudal fin base. Dorsal fin with brown base and diffuse subdistal brown band, rest of fin yellowish to pale brown in fresh material. Pectoral fin with brown melanophores on fin rays and a hyaline band along posterior margin. Pelvic fin hyaline (yellowish to pale brown in fresh material), with an irregular brown spot at base and a faint transverse brown band in middle. Anal fin with brown base and brown melanophores forming a transverse subdistal band; rest of fin hyaline (yellowish to pale brown in fresh material). Adipose fin brown, with hyaline distal margin, rest of fin yellowish to pale brown in fresh material. Caudal fin with scattered brown melanophores, a hyaline spot at base of each lobe and tips of lobes hyaline (yellowish in fresh material, with prominent dark outline). Maxillary and nasal barbels brown dorsally, beige ventrally.

Distribution. – Known from the Ataran, Salween and Sittang River drainages in Myanmar and western Thailand ( Fig. 2 ). Etymology. – From the Latin ruga, meaning crease, and mentum, meaning chin. The name is a noun in apposition and refers to the presence of unculiferous skin ridges on the gular region.

Figures

Fig. 1. Glyptothorax rugimentum, new species, holotype, ZRC 50572, 78.6 mm SL; Myanmar: Ataran River. Dorsal, lateral and ventral views.

Fig. 2. Map showing collecting localities of Glyptothorax rugimentum, new species. Open circle denotes type locality.