Starfish Starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or "basket stars". About 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the intertidal zone down to abyssal depths, below the surface. Starfish are marine invertebrates. They typically have a central disc and five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth,
Rump (animal) Rump (animal) 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