Glyptothorax radiolus, Ng, Heok Hee, 2013

Ng, Heok Hee, 2013, Glyptothorax radiolus, a new species of sisorid catfish (Osteichthyes: Siluriformes) from northeastern India, with a redescription of G. s t r i a t u s McClelland 1842, Zootaxa 3682 (4), pp. 501-512 : 502-505

Glyptothorax radiolus , new species

( Figs. 1 , 2 )

Glyptothorax striatus (in part)— Ng & Lalramliana, 2012a: 8; 2012b: 51.

Type material. Holotype: UMMZ 249560, 118.9 mm SL; India: West Bengal, Jayanti area, Raidak II River in the vicinity of Buxa Tiger Reserve; A. Rao, 2004.

Paratype: UMMZ 245904 (1), 113.6 mm SL; data as for holotype.

Diagnosis. Glyptothorax radiolus is diagnosed from congeners in the Indian subcontinent except from G. a t e r, G. b re v i p i n n i s, G. churamanii , G. j a y a r a m i, G. pantherinus , G. pectinopterus and G. striatus in having (vs. lacking) a prominently plicate ventral surface of the pectoral-fin spine and the first pelvic-fin ray. It differs from G. a t e r, G. brevipinnis , G. churamanii , G. j a y a r a m i, G. nelsoni , G. pantherinus , G. pectinopterus , G. s a i s i i and G. striatus in having a more slender body (depth at anus 11.2–11.4% SL vs. 11.7–16.4) and the following combination of characters: eye diameter 6.6–7.4% HL interorbital distance 28.3–28.7% HL, head length 23.7–24.3% SL, wedgeshaped central depression in thoracic adhesive apparatus devoid of skin ridges, unculiferous ridges of thoracic adhesive apparatus not extending anteriorly onto gular region, pectoral-fin length 21.4–22.8% SL, dorsal-fin spine length 11.6–13.9% SL, dorsal-to-adipose distance 26.6–26.8% SL, pelvic-fin length 16.5–18.3% SL, adipose-fin base length 13.1–14.3% SL, anal-fin base length 13.4–14.0% SL, caudal-peduncle length 20.9% SL, caudalpeduncle depth 7.7% SL (1.4–1.5 times in body depth at anus), absence of distinct pale midlateral stripe on body, and 36 total vertebrae.

Description. Morphometric data as in Table 1 . Head depressed, body subcylindrical. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile flat to anal-fin base, 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. Caudal peduncle long and thin, depth 1.4–1.5 times in body depth at anus. Skin almost smooth, with minute tubercles on sides of body. Lateral line complete, mid-lateral. Vertebrae 18+18=36 (2).

Head depressed, broad; triangular in lateral view. Snout prominent. Anterior and posterior nares large, 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, its horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel long slender; extending to middle of pectoral-fin base. Nasal barbel slender, extending to midway 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 origin posterolateral of inner mandibular barbel, extending to two-thirds of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band not exposed with mouth closed. Oral teeth small, villiform; in irregular rows on all tooth-bearing surfaces. Premaxillary teeth in a single broad semilunate band. Dentary teeth in two narrow crescentic bands separated at midline.

Thoracic adhesive apparatus present, consisting of ridges of skin (plicae) in rhomboidal field extending from isthmus to level of middle of pectoral-fin base, with wedge-shaped median depression on posterior half open caudally. Plicae uninterrupted; medial plicae orientated anteriorly, lateral ones anterolaterally.

Pectoral fin with I,8,ii (2) rays; posterior fin margin slightly concave. Pectoral spine very broad and covered with thick skin; ventral surface of spine with prominent plicae ( Fig. 2 a). Anterior spine margin smooth, its posterior margin with 9–11 serrae. Dorsal fin above anterior third of body, with I,6 (2) rays; fin margin convex; spine broad, straight; with smooth posterior margin. Vertical through pelvic-fin origin posterior to that through posterior end of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (2) rays, ventral surface of first ray with prominent plicae ( Fig. 2 b); tip of adpressed fin not reaching anal-fin origin. Adipose fin with anterior margin straight or very slightly concave, posterior margin angular. Vertical through anal-fin origin posterior to that through adipose-fin origin. Anal fin with straight anterior margin, straight or slightly concave posterior margin; with iii,9,i* (1) or iv,9 (1) rays. Caudal fin strongly forked, with lower lobe very slightly longer than upper lobe and i,7,8,i (2) principal rays. Procurrent rays symmetrical, extending only slightly anterior to fin base.

Coloration. In 70% alcohol: dorsal and lateral surfaces of head and body brown, fading to light grayish brown on ventral surfaces. Distinct pale mid-dorsal stripe on dorsal surface of body. Posterior half of supraoccipital process, both central portion and lateral tips of nuchal plate elements with light brown spots. Dorsal, pectoral, pelvic, anal and caudal fins also brown, particularly on rays. Adipose fin brown basally, fading to lighter brown along distal margin. Nasal and maxillary barbels brown dorsally, light grayish brown ventrally; all mandibular barbels light brown.

Etymology. The specific name comes from the diminutive form of the Latin noun radius, meaning a ray or rod, in allusion to narrow, elongate appearance of this species.

Distribution. Known from the Raidak River drainage, a right-bank tributary of the Brahmaputra River, in West Bengal, India ( Fig. 3 ).

Figures

FIGURE 1. Glyptothorax radiolus, UMMZ 249560, holotype, 118.9 mm SL; dorsal, lateral and ventral views.

FIGURE 2. Glyptothorax radiolus, UMMZ 245904, 113.6 mm SL; ventral views of: a. right pectoral fin, b. right pelvic fin, showing plicae on the first fin elements.

FIGURE 3. Map showing collecting localities of Glyptothorax radiolus (triangle) and G. striatus (circles).

Tables

TABLE 1. Biometric data for Glyptothorax radiolus (n = 2).

Standard length (mm) Percent of standard length Predorsal length Preanal length Prepelvic length	Holotype UMMZ 249560 118.9 34.7 63.8 43.7	Paratype UMMZ 245904 113.6 33.1 67.0 48.8
Prepectoral length Dorsal-fin base length	21.2 12.3	21.0 13.4
Dorsal-spine length Anal-fin base length Pelvic-fin length Pectoral-fin length	11.6 14.0 16.5 21.4	13.9 13.4 18.3 22.8
Pectoral-spine length Caudal-fin length	15.4 22.6	15.9 24.9
Adipose-fin base length Dorsal-to-adipose distance Post-adipose distance Caudal-peduncle length	13.1 26.8 21.3 20.9	14.3 26.6 20.2 20.9
Caudal-peduncle depth Body depth at anus	7.7 11.2	7.7 11.4
Head length Head width Head depth Percent of head length Snout length Interorbital distance	24.3 19.1 12.4 47.8 28.7	23.7 18.8 11.5 52.0 28.3
Eye diameter Nasal barbel length Maxillary barbel length Inner mandibular barbel length Outer mandibular barbel length	6.6 28.0 97.5 32.9 36.3	7.4 24.2 101.1 37.9 62.8