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.
