Ordovician Period to present, 472-0 Ma Crinoids thrived in the Ordovician period, and after going through two abrupt periods of adaptive radiation, still exist today. In terms of anatomy, the stem, crown, and arms are the crinoid’s main components. Like their relatives the starfish, crinoids filter plankton and small particles of detritus with their arms. Their habitats are primarily in the deep sea and coral reefs. Many fossils have been found in Germany, Ohio, and Utah.
