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In Forcipulatida, such as Asterias and Pisaster, they occur in pompom-like tufts at the base of each spine, whereas in the Goniasteridae, such as Hippasteria phrygiana, the pedicellariae are scattered over the body surface.Some are thought to assist in defence, while others aid in feeding or in the removal of organisms attempting to settle on the starfish's surface.
They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface. They typically have a central disc and five arms, though some species have a larger number of arms.
Pedicellariae are compound ossicles with forceps-like jaws.
They remove debris from the body surface and wave around on flexible stalks in response to physical or chemical stimuli while continually making biting movements. Paxillae are umbrella-like structures found on starfish that live buried in sediment.
Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding.
They have complex life cycles and can reproduce both sexually and asexually.
Most can regenerate damaged parts or lost arms and they can shed arms as a means of defence.