Pelvic fins with one spine and three (Naso and Paracanthus) or (usually) five soft rays; dorsal fin usually with 4-9 spines and 19-31 soft rays; anal fin with two or three spines and usually 19-36 soft rays.
Six genera and about 80 species. The subfamilies and tribes are recognized after a 1993 study of R. Winterbottom. From the rich Eocene and Oligocene fossil record, it appears that the group was as diversified then as it is now (J. C. Tyler has many papers describing the fossil record, e.g., Tyler, 2000).
Subfamily Nasinae (Unicornfishes). Two anal spines, three soft pelvic rays rather than five in addition to the spine, one or two plates on the caudal peduncle, and some species with a protuberance on the frontal region developing with age; four branchiostegal rays. Indo-Pacific.
One genus, Naso (including the subgenus Axinurus), and about 16 species (Borden, 1998; Randall, 2001b, c).
Subfamily Acanthurinae. Three anal spines; one or more movable spines (fixed in Prionurus) on caudal peduncle, which, when extended, can form a formidable weapon (in a deep groove in the Acanthurini); five branchiostegal rays; jaw teeth spatulate. Maximum length about 66 cm.
There are three recognized tribes with five genera and about 64 species (e.g., Randall, 2001c,d; Randall and Earle, 1999; Randall and Clements, 2001).
Prionurini (primarily Pacific), with Prionurus (three anal spines and 3-10 bony plates on the caudal peduncle).
Zebrasomini with two genera, Paracanthus and Zebrasoma (tangs). Acanthurini with two genera, Acanthurus and Ctenochaetus.
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