High Quality Content by WIKIPEDIA articles! The rump or croup, in the external morphology of an animal, is the portion of the posterior dorsum that is posterior to the loins and anterior to the tail. Anatomically, the rump corresponds to the sacrum.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 certain 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).Anatomy of the horse, rear viewSome 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.