Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate.

The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather sparse, as starfish tend to disintegrate after death. The tropical crown-of-thorns starfish ( Acanthaster planci) is a voracious predator of coral throughout the Indo-Pacific region, and the Northern Pacific seastar is on the list of the World's 100 Worst Invasive Alien Species. Starfish, such as the ochre sea star ( Pisaster ochraceus) and the reef sea star ( Stichaster australis), have become widely known as examples of the keystone species concept in ecology. The Asteroidea occupy several significant ecological roles. Most can regenerate damaged parts or lost arms and they can shed arms as a means of defense. They have complex life cycles and can reproduce both sexually and asexually. Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding. They are opportunistic feeders and are mostly predators on benthic invertebrates. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. They typically have a central disc and usually five arms, though some species have a larger number of arms. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. Starfish are also known as asteroids due to being in 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. Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea ( / ˌ æ s t ə ˈ r ɔɪ d i ə/).

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