Editing Crinoid (section)

=== Diversity ===
Echinoderms with mineralized skeletons entered the fossil record in the early [[Cambrian]] (540 mya), and during the next 100 million years, the crinoids and blastoids (also stalked filter-feeders) were dominant.<ref name="Waggoner">{{cite web |url=http://www.ucmp.berkeley.edu/echinodermata/echinofr.html |title=Echinodermata: Fossil Record |author=Waggoner, Ben |date=16 January 1995 |work=Introduction to the Echinodermata |publisher=Museum of Paleontology: University of California at Berkeley |access-date=30 March 2019}}</ref> At that time, the Echinodermata included twenty taxa of [[Class (biology)|class]] rank, only five of which survived the mass extinction events that followed. The long and varied geological history of the crinoids demonstrates how well the echinoderms had adapted to filter-feeding.<ref name=Ruppert/>

The crinoids underwent two periods of abrupt [[adaptive radiation]], the first during the Ordovician (485 to 444 mya), and the other during the early Triassic (around 230 mya).<ref name=Foote1999>{{cite journal | last= Foote |first=Mike | year = 1999 | title = Morphological diversity in the evolutionary radiation of Paleozoic and post-Paleozoic crinoids | journal = Paleobiology | volume = 25 | issue = sp1 | pages = 1–116 | doi = 10.1666/0094-8373(1999)25[1:MDITER]2.0.CO;2 | jstor = 2666042 |s2cid=85586709 | issn = 0094-8373}}</ref> This Triassic radiation resulted in forms possessing flexible arms becoming widespread; [[motility]], predominantly a response to predation pressure, also became far more prevalent than sessility.<ref name=Baumiller2008>{{cite journal |doi=10.1146/annurev.earth.36.031207.124116|title=Crinoid Ecological Morphology|journal=Annual Review of Earth and Planetary Sciences|volume=36|pages=221–249|year=2008|last1=Baumiller|first1=Tomasz K.|bibcode=2008AREPS..36..221B}}</ref> This radiation occurred somewhat earlier than the [[Mesozoic marine revolution]], possibly because it was mainly prompted by increases in benthic predation, specifically of echinoids.<ref name="Baumiller2010">{{cite journal |doi=10.1073/pnas.0914199107 |title=Post-Paleozoic crinoid radiation in response to benthic predation preceded the Mesozoic marine revolution |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=13 |pages=5893–5896 |year=2010 |last1=Baumiller |first1=T. K. |last2=Salamon |first2=M. A. |last3=Gorzelak |first3=P. |last4=Mooi |first4=R. |last5=Messing |first5=C. G. |last6=Gahn |first6=F. J. |bibcode=2010PNAS..107.5893B |pmid=20231453 |id={{INIST|22572914}} |jstor=25665085 |pmc=2851891|doi-access=free }}</ref> There then followed a selective [[Permian–Triassic extinction event|mass extinction]] at the end of the [[Permian]] period, during which all blastoids and most crinoids became extinct.<ref name=Foote1999/> After the end-Permian extinction, crinoids never regained the morphological diversity and dominant position they enjoyed in the Paleozoic; they employed a different suite of ecological strategies open to them from those that had proven so successful in the Paleozoic.<ref name=Foote1999/>