Chaca serica

description

Description. Head and anterior half of body to region between pelvic- and anal-fin bases strongly depressed; body posterior to region between pelvic- and anal-fin bases compressed. Head appearing square in dorsal view, with snout truncate or slightly convex. Anterior naris located on anterior margin of snout; naris tubular and directed anteriorly. Posterior naris ovoid and subtended anterolaterally by small nasal barbel. Maxilla strongly developed and prominent as convex lobe at lateral margin of upper jaw. Dorsal surface of neurocranium covered with thick, tuberculate skin. Small, fimbriate skin flaps covering parts of dorsal and lateral surfaces of head, particularly in buccal region and along lateral margins. Supraoccipital process relatively short, contacting anterior nuchal plate element. Eye small and ovoid, horizontal axis longest; dorsally directed and located at about anterior third of head. Gill openings narrow, extending from posttemporal to just ventral to base of pectoral spine. Mouth superior; lower jaw slightly longer than upper. Oral margin of lower lip relatively smooth, lacking rugose ridges. Oral teeth small, villiform, in irregular rows on all tooth-bearing surf

Chaca serica, a new species of frogmouth catfish (Teleostei: Siluriformes) from southern Borneo

diagnosis

Diagnosis. Chaca serica is distinguished from C. bankanensis in lacking (vs. having) a series of rugose ridges on the oral margin of the lower lip (Fig. 3), and generally longer dorsal and ventral procurrent caudal-ray bases (32.8 – 37.3 % SL vs. 29.4 – 32.8 and 16.0 – 19.2 % SL vs. 13.6 – 16.3 respectively), and from both C. burmensis and C. chaca in having (vs. lacking) nasal barbels, four (vs. five) pectoral-fin rays, and lacking (vs. having) a row of fimbriate skin flaps on the body dorsal to (and sometimes ventral to) the lateral line. It additionally differs from C. burmensis in having (vs. lacking) papillae around the eyes, a temporal fossa extending (vs. not extending) to the supraoccipital, and fewer serrae on the anterior edge of the pectoral spine (7 – 8 vs. 11 – 19).

Chaca serica, a new species of frogmouth catfish (Teleostei: Siluriformes) from southern Borneo

distribution

Distribution. Chaca serica is known from the Barito, Kahayan, Kapuas (not to be confused with the larger river with an identical name in western Borneo) and the Mentaya river drainages in southern Borneo (Fig. 4).

Chaca serica, a new species of frogmouth catfish (Teleostei: Siluriformes) from southern Borneo

etymology

Etymology. The specific epithet comes from the Latin adjective sericus meaning made of silk, or silken, in allusion to the smooth oral margin of the lower lip when compared to C. bankanensis, the congener that it superficially resembles most.

Chaca serica, a new species of frogmouth catfish (Teleostei: Siluriformes) from southern Borneo