The butterflyfishes are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfishes and coralfishes are also included in this group. The approximately 120 species in 10 genera are found mostly on the reefs of the Atlantic, Indian, and Pacific Oceans. A number of species pairs occur in the Indian and Pacific Oceans, members of the huge genus Chaetodon. Butterflyfishes look like smaller versions of angelfish (Pomacanthidae), but unlike these, lack preopercle spines at the gill covers. Some members of the genus Heniochus resemble the Moorish idol (Zanclus cornutus) of the monotypic Zanclidae. Among the paraphyletic Perciformes, the former are probably not too distantly related to butterflyfish, whereas the Zanclidae seem far less close.