The whitemargin unicornfish was first formally described in 1825 as Priodon annulatus by the French naturalists Jean René Constant Quoy and Joseph Paul Gaimard with its type locality given as Timor Island.

There is a long, horizontal, tapering bony protuberance in front of the eyes, this starts of as a bump in individuals with a total length of less than 20 cm (7.9 in).

The caudal fin is trucate in juveniles but becomes scalloped in adults and the males develop long filaments from the tips of the lobes.

As the grow into adults a black submarginal band develops in the caudal fin and they retain a thin white margin and tail filaments.

[2] The white margin unicornfish has a wide distribution in the Indo-Pacific it occurs from the Red Sea and eastern coasts of Africa east as far as Cocos Island, part of Costa Rica.