Article
Article
Crinoidea
Article By:
Baumiller, Tomasz K. Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan.
Last reviewed:December 2019
DOI:https://doi.org/10.1036/1097-8542.168000
A class of exclusively suspension-feeding echinoderms with long, slender arms arranged radially around the calyx, a rigid cuplike structure composed of calcareous plates. The radial arm arrangement gives crinoids a flowerlike appearance (Fig. 1). Two basic adult body types are recognized: the sea lilies, with a long, anchored stem vertically supporting the calyx and arms above the sea bottom; and the stemless featherstars, or comatulids, with a whorl of flexible appendages on the calyx. Crinoids have a worldwide distribution and can be found in all seas except the Black and Baltic. They occupy depths ranging from just below sea level to a depth of over 9000 m (29,500 ft). Sea lilies are found only at depths greater than 100 m (330 ft), whereas comatulids are most abundant and diverse in shallow, tropical coral reef environments. See also: Blastoidea; Pelmatozoa
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