Bluespine unicornfish

   Mature fish are grey-brown. The caudal peduncle has two large, immobile, keel-shaped bony plates in adults, but these are absent in juveniles. The head of adult fish has a characteristic horn protruding forward above the eyes. It lengthens with age and is absent in young fish. Adult fish often have barbel-like extensions of the outer rays of the caudal fin.