Editing Crinoid (section)

{{Short description|Class of echinoderms}}
{{Good article}}
{{Automatic taxobox
| name = Crinoids
| fossil_range = {{fossilrange|Ordovician|recent|ref=<ref>{{cite web |title=Crinoidea – Digital atlas of Ancient life |url=https://www.digitalatlasofancientlife.org/learn/echinodermata/crinoidea/}}</ref>}}
| image = Crinoid on the reef of Batu Moncho Island.JPG
| image_caption = Crinoid on the reef of Batu Moncho Island, [[Indonesia]]
| taxon = Crinoidea
| authority = [[John Samuel Miller|Miller]], 1821<ref name=WoRMS>{{cite WoRMS |author=Hansson, Hans |year=2012 |title=Crinoidea |id=123081 |access-date=2013-01-30 |db=}}</ref>
| subdivision_ranks = Major groups
| subdivision = * †[[Camerata (crinoid)|Camerata]]
* [[Pentacrinoidea]]
** [[Articulata (Crinoidea)|Articulata]] (700 living species)
** †[[Disparida]]
** †[[Porocrinoidea]]
** †[[Flexibilia]]
}}

'''Crinoids''' are marine invertebrates that make up the [[Class (biology)|class]] '''Crinoidea'''. Crinoids that remain attached to the [[sea floor]] by a stalk in their adult form are commonly called '''sea lilies''', while the unstalked forms, called '''feather stars'''<ref>{{Cite book |last=Gordon |first=D.P. |title=New Zealand inventory of biodiversity: 1. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia |publisher=Canterbury University Press |year=2009 |isbn=978-1-877257-72-8 |location=Christchurch |pages=373}}</ref><ref name="INS-20230812">{{cite news |last1=McFall-Johnsen |first1=Morgan |last2=Lee |first2=Lloyd |title=Scientists found a new sea creature with 20 'arms' and named it after a strawberry |url=https://www.businessinsider.com/scientists-discover-new-species-of-feather-stars-with-20-arms-2023-8 |date=12 August 2023 |work=[[Insider (magazine)|Insider]] |url-status=live |archiveurl=https://archive.today/20230812155816/https://www.businessinsider.com/scientists-discover-new-species-of-feather-stars-with-20-arms-2023-8 |archivedate=12 August 2023 |accessdate=13 August 2023 }}</ref> or '''comatulids''', are members of the largest crinoid [[Order (biology)|order]], [[Comatulida]]. Crinoids are [[echinoderm]]s in the [[phylum]] [[Echinoderm]]ata, which also includes the [[starfish]], [[brittle star]]s, [[sea urchin]]s and [[sea cucumber]]s.<ref name=Ruppert/>  They live in both shallow water<ref name="Zmarzly85">{{cite journal | url=https://scholarspace.manoa.hawaii.edu/handle/10125/941 | title=The Shallow-Water Crinoid Fauna of Kwajalein Atoll, Marshall Islands: Ecological Observations, Interatoll Comparisons, and Zoogeographic Affinities | author=Zmarzly, D.L. | journal=Pacific Science | year=1985 | volume=39 | pages=340–358| hdl=10125/941 }}</ref> and in depths of over {{convert|9000|m}}.<ref name="IzuDeep">{{cite journal | title=Discovery of Dense Aggregations of Stalked Crinoids in Izu-Ogasawara Trench, Japan | author=Oji, T. | author2=Ogawa, Y. | author3=Hunter, A. W. | author4=Kitazawa, K. | name-list-style=amp | journal=[[Zoological Science]] | year=2009 | volume=26 |issue = 6| pages=406–408 | doi=10.2108/zsj.26.406|pmid = 19583499| s2cid=5991969 | doi-access=free }}</ref>

Adult crinoids are characterised by having the mouth located on the upper surface. This is surrounded by feeding arms, and is linked to a U-shaped gut, with the anus being located on the oral disc near the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, in most crinoids the five arms are subdivided into ten or more. These have feathery pinnules and are spread wide to gather [[plankton]]ic particles from the water. At some stage in their lives, most crinoids have a short stem used to attach themselves to the [[Substrate (marine biology)|substrate]], but many live attached only as juveniles and become free-swimming as adults.

There are only about 700 living species of crinoid,<ref>[https://books.google.com/books?id=lSJWDwAAQBAJ&dq=Crinoidea+700+species&pg=PT25 Reproduction and Development in Echinodermata and Prochordata]</ref> but the class was much more abundant and diverse in the past. Some thick [[limestone]] beds dating to the mid-[[Paleozoic]] [[Era (geology)|era]] to [[Jurassic]] [[Period (geology)|period]] are almost entirely made up of disarticulated crinoid fragments.<ref>{{cite journal |last1=Lucia |first1=F. Jerry |title=Diagenesis of a Crinoidal Sediment |journal=SEPM Journal of Sedimentary Research |date=1962 |volume=32 |pages=848–865 |doi=10.1306/74D70D8F-2B21-11D7-8648000102C1865D}}</ref><ref>{{cite journal |last1=Blyth Cain |first1=J. D. |title=Aspects of the depositional environment and palaeoecology of crinoidal limestones |journal=Scottish Journal of Geology |date=September 1968 |volume=4 |issue=3 |pages=191–208 |doi=10.1144/sjg04030191|bibcode=1968ScJG....4..191B |s2cid=219538295 }}</ref><ref>{{cite journal|last1=Jach|first1=Renata|date=April 2005|title=Storm-dominated deposition of the Lower Jurassic crinoidal limestones in the Krížna unit, Western Tatra Mountains, Poland|journal=Facies|volume=50|issue=3–4|pages=561–572|doi=10.1007/s10347-004-0028-3|bibcode=2005Faci...50..561J |s2cid=128947091}}</ref>