The tailhead or dock is the beginning of the tail, where the tail joins the rump. It is known also as the base or root of the tail, and corresponds to the human sacrococcygeal symphysis. In some mammals the tail may be said to consist of the tailbone (meaning the bony column, muscles, and skin) and the skirt (meaning the long hairs growing from the tailbone). In birds, similarly, the tail consists of tailbone and tailfan (tail fan).
Some animals are subjected to docking, the amputation of the tailbone at or near the dock. These include dogs, cats, sheep, pigs, and horses. Humans have a remnant tail, the coccyx, and the human equivalent of docking is coccygectomy.
Usage varies from animal to animal. Birds and cattle are said to have a rump and tailhead. Dogs are said to have a rump and dock. Horses are said to have a croup (sometimes rump), thigh or haunch, buttock, and dock.
In bird anatomy, the rump is the body immediately above the tail. The color of plumage on the rump is a characteristic widely used by ornithologists to distinguish between related species, and sometimes also between males and females of the same species. Similarly, the silhouette of the tailfan is a characteristic widely used for purposes of identification, particularly in the field.