Ompok supernus, Ng, Heok Hee, 2008

Ng, Heok Hee, 2008, Ompok supernus, a new catfish (Teleostei: Siluridae) from Borneo, Zootaxa 1877, pp. 59-68 : 60-64

Ompok supernus sp. nov.

(Figs. 2, 3a & 4)

Type material. Holotype: MZB 10983, 129.3 mm SL; Borneo: Kalimantan Tengah, Rungan River drainage in the vicinity of Tangkiling; H. H. Ng, 3 December 2007.

Paratypes: UMMZ 248564 (1), 136.8 mm SL; ZRC 51403 (2), 158.2–160.7 mm SL; data as for holotype. ZRC 51404 (9), 69.0– 105.8 mm SL; locality as for holotype; H. H. Tan, 25 January 2008. ZRC 51405 (3), 63.6–69.6 mm SL; locality as for holotype; H. H. Tan, 30 August 2007. ZRC 51406 (1), 87.2 mm SL; Borneo: Kalimantan Tengah, Rungan–Kahayan drainage, Sungai Rijak, km 84 along road from Palangkaraya to Telakin, 1°37'19.1"S 113°37'33.6"E; H. H. Tan et al., 18 September 2007.

Diagnosis. Ompok supernus can be distinguished from all Southeast Asian congeners, except for O. borneensis , O. fumidus and O. leiacanthus , in having a combination of a brown body without any melanophores forming a prominent black humeral spot (although the tympanic area appears darkened), the rictal lobes separated by a superficial groove extending from the corner of the mouth to the submandibular groove, a gape not reaching beyond the anterior border of the orbit, and 54–66 anal-fin rays. Ompok supernus differs from O. borneensis , O. fumidus and O. leiacanthus in having more dorsally-placed eyes (Fig. 2), which is also manifested in its smaller interorbital distance compared to the latter three species (42.6–48.7% HL vs. 49.1–59.5).

Ompok supernus is additionally diagnosed by a combination of a mottled body and a rounded anterior profile of the lower jaw, and further differs from O. fumidus in having a narrower head (14.7–17.4% SL vs. 17.5– 20.5).

FIGURE 2. Ompok supernus , MZB 10983, holotype, 129.3 mm SL; Borneo: Kalimantan Tengah, Rungan River drainage. Dorsal, lateral and ventral views.

Description. Biometric data in Table 1 . Body laterally compressed; maximum body depth located ventral to dorsal-fin origin; head as broad as body and slightly depressed. Dorsal profile of head slightly convex. Anterior profile of snout rounded. Anterior pair of nostrils tubular and anteromedial to maxillary barbel base. Posterior pair of nostrils bordered by fleshy dorsal and ventral membranes and posteromedial to maxillary barbel base.

Mouth terminal; gape almost horizontal, large and extending between anterior orbital margins. Welldeveloped rictal lobes present, subtended by deep submandibular groove; upper rictal lobe without skin fold.

Thin, broad supralabial fold extending from ventral to orbit to maxillary barbel base.

Jaw teeth depressible and villiform. Premaxillary teeth in narrow, slightly curved rectangular bands. Dentary teeth in similar, slightly narrower bands, narrowing posterolaterally, reaching from symphysis almost to mouth corners. First row of dentary teeth partially exposed when mouth is closed. Palatal teeth in two slightly curved arc-shaped patches on either side of midline.

Two pairs of barbels, slightly flattened along entire length. Maxillary barbels reaching to vertical through first third of anal fin. Mandibular barbels (only outer pair present) reaching to pelvic-fin origin.

Eyes small, subcutaneous (without free orbital margin); located approximately midway on head and immediately behind supralabial fold; separated from horizontal line through mouth rictus by approximately half eye diameter. Dorsal orbital margin visible dorsally; ventral orbital margin not visible ventrally.

Gill membranes separate and overlapping, free from isthmus; gular fold well-developed and v-shaped. Branchiostegal rays 9 (13) or 10* (4). Gill rakers long and thin; anteriormost rakers on lower first arch widely spaced; 1+9 (1), 2+9 (1), 3+9 (1), 2+11 (1) or 3+10* (1).

Dorsal fin small, with i,2,i (17) rays. Depressed pectoral fin to base of second anal-fin ray; distal margin broadly convex, with rounded tip. Fifth branched pectoral ray longest and fin with 11 (1), 12* (13) or 13 (3) rays. Proximal two-thirds of first pectoral-fin element co-ossified into a slender spine. Spine with shallow oblique striae on dorsal and ventral surfaces; spine in females smooth and in males with 5–7 serrations on posterior edge spanning the distal end of the ossified and proximal end of the flexible distal tip. Axillary pore small, located just dorsal to pectoral spine base. Depressed pelvic fin reaching to base of first or second analfin ray; distal margin convex with i,6 (17) rays. Distal margin of anal fin straight, with 54 (1), 55 (1), 57* (4), 58 (6), 60 (2), 61 (2) or 66 (1) rays; separate from caudal fin. Integument over anal fin thickened proximally for approximately half of ray length; fin-ray erector muscles attaching anterior edges of fin rays, ventralmost extent of muscles defined by area of thickened integument. Caudal peduncle slender. Caudal fin deeply forked, lobes elongate and with rounded tips; upper lobe slightly longer; principal rays i,5,6,i (12), i,6,5,i (1) or i,6,7,i (4).

Lateral line complete, extending to middle of caudal-fin base, with short branches along flanks directed posteroventrally. Urogenital papilla located immediately posterior to insertion of pelvic fin. Vertebrae 10+35=45 (1), 10+36=46* (2) or 10+37=47 (2).

FIGURE 3. Lateral views of heads of: a. Ompok supernus , MZB 10983, holotype, 129.3 mm SL; b. O. borneensis , ZRC 40378, 148.8 mm SL; c. O. fumidus , ZRC 15048, 118.8 mm SL and d. O. leiacanthus , ZRC 38538, neotype, 71.4 mm SL. Barbels have been cropped and images are not to scale.

Coloration. In 70% ethanol: Body and head brown, fading to yellowish white ventrally. Humeral region slightly darker than surrounding areas of body. Moderately large irregular darker brown patches on flanks extending from just dorsal to lateral line to base of anal fin (Figs. 2 and 4a). Some individuals without darker brown patches and uniform in color (Fig. 4b). Fin rays of dorsal, pectoral and caudal fins with dense concentration of melanophores, frequently imparting dark color to rays; melanophores sometimes extending to fin membranes of dorsal and pectoral fins. Melanophores much less dense on pelvic fins, imparting a dusky coloration to the fins. Anal fin also with melanophores on fin rays; melanophores more concentrated on distal edge of fin, imparting appearance of dark margin. Tips of anal-fin rays in some individuals without pigmentation, imparting appearance of very thin pale edge to anal fin. Maxillary barbels brown throughout; mandibular barbels yellowish white. Live coloration similar but darker.

FIGURE 4. Ompok supernus : a. mottled color form, ZRC 51404, paratype, 86.8 mm SL; b. uniform color form, ZRC 51404, paratype, 84.7 mm SL. Images not to scale.

Distribution. Known from the Rungan River drainage (a major tributary of the Kahayan River drainage) in southern Borneo (Fig. 5).

Habitat. Most of the type series was obtained from the aquarium trade, but a single paratype (ZRC 51406) was collected in a blackwater stream ( pH 3.4) with a sandy bottom flowing through secondary vegetation.

Etymology. From the Latin adjective supernus , meaning “that is above” or “on high”; in allusion to dorsally placed eyes of this species.

Tables

TABLE 1. Biometric data for Ompok supernus (n = 17).

	Holotype	Range	Mean±SD
% SL
Predorsal length	33.5	33.0–35.6	33.9±0.79
Preanal length	35.2	35.2–38.5	36.3±0.93
Prepelvic length	29.5	29.5–35.2	32.1±1.53
Prepectoral length	20.8	19.2–22.8	21.1±1.28
Dorsal-fin length	1.6	1.3–2.0	1.7±0.21
Anal-fin length	69.1	62.0–70.5	66.6±2.53
Pelvic-fin length	8.0	5.7–8.5	7.4±0.86
Pectoral-fin length	17.7	17.3–20.4	18.6±1.21
Pectoral-spine length	8.3	6.9–9.3	8.1±0.69
Caudal-fin length	17.5	17.5–21.5	19.4±1.45
Body depth at anus	21.7	17.2–22.6	20.6±1.81
Caudal peduncle depth	4.0	3.6–4.6	4.1±0.28
Head length	22.7	21.6–24.2	22.8±0.71
Head width	14.9	14.7–17.4	16.0±0.94
Head depth	16.2	13.6–18.4	15.9±1.27
% HL
Snout length	34.8	33.1–38.5	35.4±1.70
Interorbital distance	44.7	42.6–48.7	46.3±1.93
Eye diameter	10.9	10.5–12.7	11.1±0.69
Maxillary barbel length	235.2	184.3–257.2	219.7±22.23
Mandibular barbel length	102.7	55.6–102.7	81.2±17.50