; subclass Actinopterygii, order Perciformes)
Large family of marine, deep-bodied, and almost discus-shaped fish. They have a small, protractile mouth, minute teeth on the jaws (the name is derived from the Greek khaite, hair, and odont-, tooth), a single, continuous dorsal fin with scales along the base, and a round to notched tail fin. The family includes numerous beautiful, brightly coloured species, which are very popular among sea-water aquarium hobbyists. Among the more widely distributed butterfly fish are Chaetodon capistratus (four-eye butterfly fish) of the western Atlantic, and Chaetodon vagabundus (vagabond butterfly fish) of the Indo-Pacific and northern Australia. Angelfish, e.g. Pomacanthus imperator (emperor angelfish) of the Indo-Pacific, have a characteristic spine at the angle of the preopercle (part of the gill cover), and are often placed in a separate family, the Pomacanthidae.
Subjects: Zoology and Animal Sciences.