The family Pomacanthidae (angelfishes) is distinguished from similar families by the presence of one or more prominent spines at the angle of the preopercle (the forward, bony part of the gill cover normally separated by a groove from the rear portion). Angelfishes have a single, continuous dorsal fin; some species have filamentous extensions of one or more dorsal rays. Most angelfishes are brightly colored and several species are found in the aquarium trade. Juveniles of the genus Pomacanthus often have strikingly different color patterns than adults of the same species.