About Monotaxis heterodon (Bleeker, 1854)
Monotaxis heterodon differs from M. grandoculis, with which it was formerly considered the same species, by having 18 transverse scale rows on the cheek instead of 19. This species also has thin, vertical white bars along its upper body. Juveniles of M. heterodon differ from juveniles of M. grandoculis in having no vertical bar through the eye and no black blotches. The body of M. heterodon is overall dusky greyish, broken by thin white vertical bars along the back; these bars are only one or two scale rows wide, while they are 3-4 scale rows wide on M. grandoculis. There is a black blotch on the axil of the pectoral fin. The lips are brownish to reddish, and the fins are tinged yellowish to reddish. Monotaxis heterodon occurs in the Indian and Pacific Oceans. In the Indian Ocean, it is found at the Seychelles, Maldives, Sri Lanka, Christmas Island, and the Cocos (Keeling) Islands. It occurs across all the islands of Indonesia, extending east into the Pacific Ocean where its range reaches east to Fiji, and south to the Great Barrier Reef, Lord Howe Island, and New Caledonia. This species inhabits sheltered coral reefs at depths down to 25 m (82 ft).
