horn (Scope note)

Horns, pointed projections found on the head of many Bovidae, are two-part structures: a covering of keratin and other proteins surrounding a core of live bone. True horns are found mainly among the ruminant artiodactyls in the Bovidae (cattle, goats, antelope etc.) and Antilocapridae (pronghorn) families. One pair of horns is usual, however, two or more pairs occur in a few wild species and domesticated breeds of sheep. Horns often have a curved or spiral shape, sometimes with ridges or fluting. In many species only males have horns. Horns start to grow soon after birth, and continue to grow throughout the life of the animal, except in pronghorns, which shed the outer layer and regrow the horn sheath each year, but retain the bony core.