The Dall sheep (originally Dall's sheep), Ovis dalli, is a species of sheep native to northwestern North America, ranging from white to slate brown in color and having curved yellowish brown horns. Its closest relative is the more southern subspecies, Stone sheep (also spelled Stone's sheep) (Ovis dalli stonei), which is a slaty brown with some white patches on the rump and inside the hind legs.Research has shown the use of these subspecies designations is questionable.