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Diagnosis: scales parallel-striated; last unbranched dorsal-fin ray heavily ossified and unserrated; 5 unbranched dorsal rays in total; 30-33 lateral line scales (Ref. 75045).
Description: body slightly compressed; body depth approximately equal to head length in smaller specimens, becoming proportionately deeper with size to approximately 1.5 times head length in adults, deepest at origin of dorsal fin; head length 4 times in standard length, head depth approximately 3/4 head length; dorsal profile of head in larger specimens straight to slightly concave, shallowly convex in smaller specimens; eyes lateral in position, visible from above and below, becoming proportionately smaller in large specimens; snout pronounced, particularly in larger specimens, longer than orbit diameter in fish over 40mm SL, shorter than orbit diameter in smaller specimens; small conical tubercles present on snout, operculum and sides of head, not extending on to dorsal surface of head or on to body; nostrils prominent, short tubular anterior naris adjacent to open posterior naris and separated by raised rounded septum; nostrils at horizontal through dorsal half of eye, separated from orbit by less than one orbit radius; mouth not reaching below anterior border of orbit; lips variable, ranging from specimens with straight, keratinised scraping edge to the lower lip (Varicorhinus-like) to specimens with rounded, fleshy lips; 2 pairs of barbels, anterior just over half length of posterior, which ranges from being equal to orbit diameter in largest specimens examined to less than one-half orbit diameter in smallest specimens; gill cover opening from level with dorsal margin of orbit, attached ventrally close to isthmus; robust gill rakers on anterior arch; pharyngeal bones robust with pharyngeal teeth in three rows; origin of dorsal fin equidistant between tip of snout and base of caudal fin, positioned before origin of pelvic fins, last simple ray of dorsal fin heavily ossified and unserrated, anterior branched ray longest; distal margin of dorsal fin strongly concave; pectoral fins falcate, reaching 3/4 of distance to base of pelvic fins; pelvic fins pointed with square distal margin, reaching 2/3 of distance to base of anal fin; anal fin last unbranched ray longest; distal margin of anal fin shallowly concave, reaching to 1/2 length of caudal peduncle; single rows of prominent tubercles present on posterior edge of branched rays of anal fin in adult males; outer rays of caudal fin nearly four times length of median rays, lobes pointed; caudal peduncle of moderate length, depth generally more than 60% of length; anus and genital opening located at anterior of base of anal fin; gut extended and involuted, its length several times longer than standard length; scales moderately large, cycloid and rounded, well developed in regular rows; scales with numerous parallel striations on exposed field, less numerous on medial area of embedded field, focus ill-defined; lateral line complete, anteriorly dipping one scale row below midline, which it rejoins anterior to anal fin, passing mid-laterally to base of caudal fin; elongated pelvic axil scale present; breast scales well developed but markedly reduced in size between bases of pectoral fins (Ref. 75045). Coloration: alive: silvery-olive dorsally, silver laterally and ventrally with faint purple sheen that is most prominent on operculum; dorsal and caudal fins dark olive-grey; anal, pelvic and pectoral fins paler with brownish-orange bases, greyish extremities (Ref. 75045). Preserved specimens: scales on dorsal surface lightly pigmented with fine melanophores, more closely spaced at anterior border of exposed part of scale; pigmentation less intense ventral to lateral line scales with melanophores confined to anterior of exposed part of scale; ventral scales unpigmented; vertical crescent of dark pigment behind operculum from lateral line to pectoral fin base; fin membranes between rays of dorsal, caudal and pectoral fins heavily pigmented, outlining the rays; similar pigment appears on pelvic and anal fins, but less prominently; caudal fin with fine, dark posterior edge as result of membrane pigmentation; dorsal surface of head very finely pigmented, with larger melanophores in the centre of operculum; posterior edge of operculum unpigmented; ventral surface of head, lips and barbels unpigmented (Ref. 75045). |