By Keiichi Matsuura

Triacanthus biaculeatus

Triacanthus nieuhofi

Small fishes less than 30 cm, with moderately elongate, strongly compressed body covered by moderately thick skin with numerous minute scales. Mouth small and terminal; teeth in an outer series of about 10 heavy incisors in each jaw, internally to which are several molariform teeth, usually 4 in upper jaw and 2 in lower jaw. Gill opening a moderately short vertical slit in front of pectoral-fin base. Dorsal fin spine VI (usually only V visible, the sixth rudimentary), dorsal- fin rays 20 to 26; caudal fin deeply forked; pelvic fins with I large spine and no visible rays; most dorsal-, anal, and pectoral-fin rays branched. Caudal peduncle distinctly tapering to a narrow transversely indented region just in front of caudal-fin base, where the peduncle is wider than deep. Lateral line inconspicuous. Color: generally silvery, with upper half of body dusky, with or without darker blotches.

Similar families occurring in the area. Triacanthodidae: caudal fin not deeply forked, rounded to almost truncate; caudal peduncle not distinctly tapered, deeper than wide; dorsal-fin rays 12 to 18 (20 to 26 in Triacanthidae).

Remarks. Benthic, occurring usually on flat, sandy or weed-covered bottoms. Feed on bottom invertebrates. Marketed but not commercially important.