Horns versus Antlers
Antlers—found on members of the deer family—grow as an extension of the animal’s skull. They are true bone, are a single structure, and, generally, are found only on males.
Horns—found on pronghorn, bighorn sheep, and bison—are a two-part structure. An interior portion of bone (an extension of the skull) is covered by an exterior sheath grown by specialized hair follicles (similar to human fingernails). Horns are usually found on both males and (in a diminutive form) females.
Antlers are shed and regrown yearly while horns are never shed and continue to grow throughout an animal’s life. One exception is the pronghorn, which sheds and regrows its horn sheath each year.