Pseudomystus tuberosus, Ng & Tan, 2024

Ng, Heok Hee & Tan, Heok Hui, 2024, Pseudomystus tuberosus, a new species of catfish from central Borneo (Actinopterygii: Bagridae), Zootaxa 5496 (4), pp. 546-554 : 547-549

Pseudomystus tuberosus , new species

Fig. 1

Holotype. MZB 17244 , male, 93.0 mm SL; Borneo: Kalimantan Tengah, Kahayan River drainage, Rungan River sub-drainage, stream near Tangkiling; H. H. Tan, 10 July 2014.

Paratypes. ZRC 54541 (2), 79.7–88.1 mm SL; data as for holotype .

Diagnosis. Pseudomystus tuberosus can be distinguished from congeners in having a strongly humped dorsal profile (vs. weakly humped or without hump), and its head and flanks covered with rounded tubercles (vs. with smooth or with capillaceous epithelial projections). It additionally differs from congeners in having the following unique combination of characters: eye diameter 8% HL; head width 18.5–19.7% SL; head depth 15.8–16.0% SL; 12–14 rakers on first gill arch; posttemporal process indistinct, not as long as postcleithral process; dorsal margin of postcleithral process slightly concave; length of pectoral-fin spine 15.4–16.7% SL; 17–18 serrations on posterior margin of pectoral spine; length of dorsal-fin spine 18.5–22.4% SL; body depth at anus 14.2–16.0% SL; length of adipose-fin base 23.3–26.1% SL; posterior insertion of adipose fin separate from dorsal procurrent caudal-fin rays; caudal peduncle depth 5.5–6.0% SL; tubular extensions of laterosensory canals on body absent; dark-colored body with pale patches on flanks; caudal fin without dark submarginal longitudinal band running along both lobes; and 43–44 vertebrae.

Description. Morphometric data as in Table 1. Head depressed; dorsal profile slightly concave, with distinct nuchal hump. Ventral profile almost straight. Snout broadly rounded when viewed dorsally. Bony elements of dorsal surface of head covered with thin skin; bones visible, especially on posterior half of neurocranium, and ornamented with numerous fine, radial grooves. Midline of cranium with fontanelle extending from behind snout to beyond level of posterior orbital margin. Supraoccipital process broad, with gently converging sides and emarginate tip; not reaching nuchal plate. Eye ovoid, horizontal axis longest, subcutaneous; located entirely in dorsal half of head. Gill openings wide, extending from post-temporal to beyond isthmus. Gill membranes free from isthmus, with 8 (3) branchiostegal rays. First branchial arch with 4+8 (1), 4+9 (1) or 4+10* (1) gill rakers.

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Mouth subterminal. Oral teeth small, villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band rounded, of uniform width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Vomerine tooth band unpaired, continuous across midline; smoothly arched along anterior margin, tapering laterally to point extending posteriorly past level of premaxillary band; band width narrower than premaxillary band at midline, widening laterally, then tapering to a sharp point postero-laterally.

Barbels in four pairs. Maxillary barbel slender, extending for four-fifths of head length. Nasal barbel slender, extending to one third of distance between posterior orbital margin and dorsalmost extent of gill opening. Inner mandibular-barbel origin close to midline, thicker and longer than nasal barbel, extending for half of head length. Outer mandibular barbel originating postero-lateral of inner mandibular barbel, extending for three quarters of head length.

Body slightly compressed, becoming more so toward caudal peduncle. Dorsal profile gently concave from tip of snout to nuchal region, distinctly humped from nuchal region to origin of dorsal fin, sloping gently ventrad from origin of dorsal fin to end of caudal peduncle. Ventral profile slightly convex to anal-fin base, then sloping slightly dorsally to end of caudal peduncle. Skin smooth, with rounded tubercles; projections especially prominent on head and flanks. Lateral line complete, mid-lateral in position. Vertebrae 17+26=43 (1) or 19+25=44* (2).

Dorsal fin with spinelet, spine, and 7 (3) rays. Origin of dorsal fin anterior to mid-body, about two-fifths of body. Dorsal fin margin convex, anterior branch of fin rays usually longer than other branches. Dorsal fin spine of moderate length, straight, slender, posterior edge without serrations. Nuchal plate broadly ovoid.

Pectoral fin with stout spine, sharply pointed at tip, and 8 (3) rays. Anterior spine margin smooth; posterior spine margin with 17–18 large serrations along entire length. Pectoral fin margin straight anteriorly, convex posteriorly. Cleithral process moderately broad, with slightly concave dorsal margin, extending for two thirds of pectoral-spine length.

Pelvic fin with origin at vertical through posterior end of dorsal-fin base, with i,5 (3) rays, its margin slightly convex; tip of adpressed fin reaching slightly beyond anal-fin origin. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Males with short, conical genital papilla.

Adipose fin with convex margin for entire length, with deeply incised posterior portion and origin, separate from base of last dorsal-fin ray; fin base of moderate length, spanning half of postdorsal distance. Anal fin originating just posterior to vertical through origin of adipose fin, with iv,11,i* (1) or v,10,1 (2) rays, posterior margin curved.

Caudal peduncle slender. Caudal fin deeply forked, with i,7,8,i (3) principal rays; upper lobe slender, pointed, lower lobe rounded. Procurrent rays extend anterior to fin base.

Coloration. In 70% ethanol: head and body dark brownish-gray above, fading on sides of head and abdomen; cream on ventral surfaces. Caudal fin hyaline with diffuse chocolate-brown color on proximal half of fin rays on each lobe. Irregular, wavy yellowish bar over nape. Series of yellowish patches on body: first patch ovoid, behind tympanic region and below dorsal fin; second patch ovoid, on dorsal surface of body at base of last dorsal-fin ray; third patch ovoid, at pelvic-fin base; fourth patch consisting of two coalescent ovoid patches on flank posterior to dorsal-fin base and between pelvic- and anal-fin origins; fifth patch narrowly ellipsoid on dorsal surface of adipose fin at its anterior origin; sixth patch consisting of two coalescent ovoid patches on caudal peduncle, extending into posteroventral corner of adipose fin. Dorsal and anal fins hyaline with chocolate-brown basal, and diffuse brown submarginal bars. Pelvic fin hyaline with diffuse chocolate-brown color on proximal half of fin rays. Posterior edge of adipose fin hyaline. Coloration in life unknown.

Distribution. Known from the Kahayan River drainage in south central Borneo ( Fig. 2 ).

Etymology. The Latin adjective tuberosus (-a, -um) means “full of humps, lumps and protuberances”. The name is used in reference to both the distinctively humpbacked appearance of this species, as well as its tuberculate head and flanks.

Figures

FIGURE 1. Pseudomystus tuberosus, holotype, MZB 17244, 93.0 mm SL; Borneo: Kalimantan Tengah, Kahayan River drainage.

FIGURE 2. Map showing collecting locality of Pseudomystus tuberosus.