antler grows from an attachment point on the skull called a pedicle. While an antler is growing it is covered with highly vascular skin called velvet, which supplies oxygen and nutrients to the growing bone. Antlers are considered one of the most exaggerated cases of male secondary sexual traits in the animal kingdom, and grow faster than any other mammal bone. Growth occurs at the tip, initially as cartilage that is then mineralized to become bone. Once the antler has achieved its full size the velvet is lost and the antler's bone dies. This dead bone structure is the mature antler. In most cases the bone at the base is destroyed by osteoclasts and the antlers eventually fall off. As a result of their fast growth rate antlers place a substantial nutritional demand on deer; they thus can constitute an honest signal of metabolic efficiency and food gathering capability. Ossicones are horn-like (or antler-like) protuberances found on the heads of giraffes and male okapis. They are similar to the horns of antelopes and cattle save that they are derived from ossified cartilage, and that the ossicones remain covered in skin and fur rather than horn. Pronghorn cranial appendages are unique. Each "horn" of the pronghorn is composed of a slender, laterally flattened blade of bone that grows from the frontal bones of the skull, forming a permanent core. As in the Giraffidae, skin covers the bony cores, but in the pronghorn it develops into a keratinous sheath that is shed and regrown on an annual basis. Unlike the horns of the family Bovidae, the horn sheaths of the pronghorn are branched, each sheath possessing a forward-pointing tine (hence the name pronghorn). The horns of males are well developed. See also Altungulata References External links Your Guide to the World's Hoofed Mammals - The Ultimate Ungulate Page Extant Paleocene first appearances Taxa named by Carl Linnaeus