There is much controversy regarding the systematics of sheep. Ovis in the species O. ammon, and all members of Pachyceros in O. canadensis. In any given population, males average larger than females.
Coloration varies from creamy white to dark gray and brown.
Some males possess a fringe of long hair down the front of the neck, but they do not have a beard such as is present in Capra. Also unlike all goats, there is no gland at the base of the tail. Ovis has a narrow nose and pointed ears. The horns of females are much smaller and only slightly curved. Some domestic breeds are hornless.