Crinoids

Crinoids

Crinoids (Crinoidea) are a class of marine animals belonging to the phylum Echinodermata.

Crinoids are sessile (fixed) or vagile (mobile) animals resembling plants, but with an articulated calcareous skeleton, a sort of « root » (possibly placed at the end of a « stem »), and a « calyx » with long flexible arms that allow them to filter the plankton they feed on from the water.

Being echinoderms, their closest relatives in the living world are sea urchins, starfish, brittle stars, and sea cucumbers. The first crinoids are attested in the Ordovician, a period beginning about 500 million years ago. Despite a morphology reminiscent of that of a plant – a form to which they owe the common name of « sea lilies » – crinoids (from the Greek krinon, lily, and eidos, form) are animals (metazoans).