Menu principale:
Various ungulate mammals present a bone appendix called horn, having various sizes and shapes: conical, cylindrical pointed at the extremity, straight, curved, spiral, branched, and so on. The horns are usually equal in many species, which possess a couple of elements protruding from the dorsal surface of the head, while in some cases there is a unique horn. Some horns are made of bone, others instead of an epidermic layer of keratin.