Species: Aluterus monoceros, Unicorn filefish

Aluterus monoceros (Linnaeus, 1758)

Unicorn filefish

Body a very compressed elongated oval; a long pointed snout, snout profiles of adult - upper convex, lower concave; a small mouth that opens above center line; teeth moderately strong, six in outer row on top jaw and six or less on outer row on bottom jaw; gill opening a short slit on side before pectoral base; 2 dorsal fins, 1st with II spines, 1st long, slender, smooth, over eye, erectile, can be locked in position by minute 2nd spine; second dorsal fin 46-50 rays; anal rays 47-52; pectoral rays modally 14; median fins rays unbranched; tail base longer than deep (depth 65-95% of its length); tail fin usually shorter than snout,  18-26% of SL, with straight to slightly concave edge; pelvic fins absent, no scales encasing area where pelvics should be; scales minute, innumerable, like fine hairs, give skin a rough texture, like sandpaper;  no patch of enlarged scales above pectoral base; lateral line inconspicuous.