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Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate.
With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture.
They are opportunistic feeders and are mostly predators on benthic invertebrates.
Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding.
As well as the starfish, the echinoderms include sea urchins, sand dollars, brittle and basket stars, sea cucumbers and crinoids.
The larvae of echinoderms have bilateral symmetry, but during metamorphosis this is replaced with radial symmetry, typically pentameric.
The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates.Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown.Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface.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.