Naso (genus)
17, See text.
The unicorn fishes are 17 species of tropical, herbivorous marine surgeonfishes in the genus Naso. They are so named because of a spike that protrudes from the forehead. Some species have a bulbous protrusion rather than a pronounced spike, and some lack a spike altogether. Unicorn fishes usually have a pair of spines on each side of the tail shaft that are used for defense.