Editing Crinoid (section)

==Evolution==
{{See also|List of echinodermata orders}}

=== Origins ===
[[File:Agaricocrinus americanus Carboniferous Indiana.jpg|thumb|''[[Agaricocrinus americanus]]'', a fossil crinoid from the [[Carboniferous]] of Indiana]]
[[File:JurassicCrinoidsIsrael.JPG|thumb|Middle [[Jurassic]] ([[Callovian]]) ''Apiocrinites'' crinoid pluricolumnals from the [[Matmor Formation]] in southern Israel]]

If one ignores the enigmatic ''[[Echmatocrinus]]'' of the [[Burgess Shale]], the earliest known unequivocal crinoid groups date back to the [[Ordovician]], 480 million years ago. There are two competing hypotheses pertaining to the origin of the group: the traditional viewpoint holds that crinoids evolved from within the [[blastozoa]]ns (the [[Eocrinoidea|eocrinoids]] and their derived descendants, the [[blastoid]]s and the [[Cystoidea|cystoids]]), whereas the most popular alternative suggests that the crinoids split early from among the [[Edrioasteroidea|edrioasteroids]].<ref name="Guensburg2010">{{cite journal |doi=10.1111/j.1502-3931.2010.00220.x |title=Pelmatozoan arms from the mid-Cambrian of Australia: Bridging the gap between brachioles and brachials? Comment: There is no bridge |journal=Lethaia |year=2010 |last1=Guensburg |first1=Thomas E. |last2=Mooi |first2=Rich |last3=Sprinkle |first3=James |last4=David |first4=Bruno |last5=Lefebvre |first5=Bertrand |volume=43 |issue=3 |pages=432–440|bibcode=2010Letha..43..432G }}</ref> The debate is difficult to settle, in part because all three candidate ancestors share many characteristics, including radial symmetry, calcareous plates, and stalked or direct attachment to the substrate.<ref name="Guensburg2010"/>

=== 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/>

===Fossils===
[[File:Fossil_Crinoids.jpg|thumb|Fossil crinoids, Henan Geological Museum, Zhengzhou, China]]
Some fossil crinoids, such as ''[[Pentacrinites]]'', seem to have lived attached to floating driftwood and complete colonies are often found. Sometimes this driftwood would become waterlogged and sink to the bottom, taking the attached crinoids with it. The stem of ''[[Pentacrinites]]'' can be several metres long. Modern relatives of ''Pentacrinites'' live in gentle currents attached to rocks by the end of their stem.

In 2012, three geologists reported they had isolated complex organic molecules from 340-million-year-old ([[Mississippian (geology)|Mississippian]]) fossils of multiple species of crinoids. Identified as "resembl[ing ...] [[aromatic]] or [[polyaromatic]] [[quinone]]s", these are the oldest molecules to be definitively associated with particular individual fossils, as they are believed to have been sealed inside ossicle pores by precipitated calcite during the fossilization process.<ref>{{cite journal |doi=10.1130/G33792.1 |title=Isolation and characterization of the earliest taxon-specific organic molecules (Mississippian, Crinoidea) |journal=Geology |volume=41 |issue=3 |pages=347 |year=2013 |last1=O'Malley |first1=C. E. |last2=Ausich |first2=W. I. |last3=Chin |first3=Y.-P. |bibcode=2013Geo....41..347O }} Note that the first sentence of the phys.org article contradicts the paper itself, which reviews several isolations of molecules from particular fossils over the past decade.
*{{cite web |author=Pam Frost Gorder |date=Feb 19, 2013 |title=Ancient fossilized sea creatures yield oldest biomolecules isolated directly from a fossil |website=Phys.org |url=http://phys.org/news/2013-02-ancient-fossilized-sea-creatures-yield.html}}</ref>

Crinoid fossils, and in particular disarticulated crinoid columnals, can be so abundant that they at times serve as the primary supporting clasts in sedimentary rocks.{{citation needed|date=May 2020}} Rocks of this nature are called [[encrinite]]s.