Not a butterflyfish, though it is usually mistaken for one; the only member of its family.
To about 22 cm not counting the streamer, with a disc-shaped white body crossed by two broad black bands, a yellow saddle over the snout, a long tubular snout and the third dorsal spine drawn into a white filament that trails well past the tail. It is the only living species in the family Zanclidae and is not closely related to the butterflyfishes it resembles — its nearest relatives are the surgeonfishes. The longfin bannerfish is the usual confusion: it has a forked tail, a shorter snout and no dark band across the tail region.
It feeds mainly on sponges, working over coral and rubble in pairs or small groups, and occasionally gathers in larger aggregations. It swims continuously and rarely tolerates a direct approach, so photographs generally come from waiting on a line it is already taking. Recorded from about 2 to 45 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.