Body elongate, oval; snout pointed, slopes at about 60°; adult with long, tapering horn before eye that can extend 1 head length forward (a bump on forehead of juveniles); mouth small, protrusible, low on head; teeth small, conical, tips slightly depressed & either smooth or with multiple small points; dorsal fin VI, 28-29; anal II, 27-28; pectoral 17-19 rays; pelvics I, 3; 2 pairs of cutting keels on plates on narrow tail base; tail edge straight, a series of small scallops on rear margin, long filaments from top and bottom in males (straight in juveniles); scales very small, rough; lateral line complete.
Olive to brown; can switch on pale blue color; tail with wide rays blackish, membranes between rays, narrow margin, and filaments white. Juvenile with thin white dorsal and anal margins, a white saddle on the caudal peduncle, tail dark with white margin.
Size: 100 cm.
Habitat: juveniles and subadults benthic on reefs and rocky shores, adults in open water near exposed reef fronts.
Depth: 0-122 m; subadults usually 5-15 m, adults usually 10-30 m.
An Indo-Pacific species recorded as a vagrant from Cocos and Clipperton Atoll.