Crinoidea: Fossil Record



The earliest possible echinoderms appeared in the late Proterozoic, but there has been very little fossil material discovered until the early and middle Cambrian. Some paleontologists feel this is because early echinoderms were possibly soft bodied organisms and did not readily fossilize. Echinoderms began to appear in greater numbers during the early to middle Cambrian. The earliest fossil crinoid may have been Echmatocrinus, from the famous Burgess Shale of the middle Cambrian; some paleontologists, however, do not feel that Echmatocrinus was a true crinoid. By the beginning of the Ordovician many groups of echinoderms flourished, especially the crinoids. The crinoids were the most abundant group of echinoderms from the early Ordovician to the late Paleozoic, when they, along with the rest of the echinoderms, nearly went extinct during the Permo-Triassic extinction.Only a single genus of crinoid is known from the early Triassic, which eventually gave rise to the extant articulate crinoids.