Rump (animal)
（重定向自Tailfan）
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 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).