Siganus luridus

S. luridus is a demersal herbivorous fish commonly 5- 25 cm long. Its body is compressed, deep and ellipsoid and its standard length is 2.1-2.8 times its depth. Teeth are in jaws in one series, incisor-like with 1 or 2 lateral cusps. No teeth on the palatine or on the vomer. The longest dorsal spine is longer than distance from front of eye to posterior edge of opercula and the longest dorsal ray is longer than length of snout. It has a small first dorsal spine directed forward and is usually covered by skin. Dorsal fin origin is above pectoral fin base. Caudal fin is truncated. Anal fin origin beneath 8-10 dorsal spines;its margin is round. Pelvic fin origin is behind pectoral fin base. Head is slightly concave with blunt snout. Mouth is relatively small with distinct lips. Maxilla is not reaching vertical of eye. The caudal fin is forked. It has small embedded scales. Its colour is variable but usually a grey-green to brown back, a light-brown to yellow abdomen and fine yellow lines on each side. Pectoral fins are hyaline-yellow with dark crossbars on caudal fins.