Editing Crinoid

{{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>

==Etymology==
The name "Crinoidea" comes from the Ancient Greek word ''[[wikt:κρίνον|κρίνον]]'' (''krínon''), "a lily", with the suffix ''[[wikt:-oid#English|–oid]]'' meaning "like".<ref>''Webster's New Universal Unabridged Dictionary.'' 2nd ed. 1979.</ref><ref name=OnlineEtDict>{{cite encyclopedia|title=crinoid|url=http://www.etymonline.com/index.php?term=crinoid&allowed_in_frame=0|dictionary=[[Online Etymology Dictionary]]}}</ref>

==Morphology==
[[File:Crinoid anatomy.png|thumb|upright=1.15|Anatomy of a stalked crinoid]]
 
The basic body form of a crinoid is a stem (not present in adult feather stars) and a crown consisting of a cup-like central body known as the theca, and a set of five rays or arms, usually branched and feathery. The [[mouth]] and [[anus]] are both located on the upper side of the theca, making the [[Dorsal (anatomy)|dorsal]] (upper) surface the oral surface, unlike in the other echinoderm groups such as the [[sea urchin]]s, [[starfish]] and [[brittle star]]s where the mouth is on the underside.<ref name=OHara>{{cite book|author1=O'Hara, Timothy|author2=Byrne, Maria|title=Australian Echinoderms: Biology, Ecology and Evolution |url=https://books.google.com/books?id=EtkqDwAAQBAJ&pg=PA171 |year=2017 |publisher=Csiro Publishing |isbn=978-1-4863-0763-0 |pages=171–180}}</ref> The numerous calcareous plates make up the bulk of the crinoid, with only a small percentage of soft tissue. These ossicles fossilize well and there are beds of limestone dating from the [[Mississippian (geology)|Lower Carboniferous]] around [[Clitheroe]], England, formed almost exclusively from a diverse fauna of crinoid fossils.<ref name=HessBrett>{{cite book|author1=Hess, Hans |author2=Brett, Carlton E. |author3=Ausich, William I.|author4=Simms, Michael J.|title=Fossil Crinoids|url=https://books.google.com/books?id=TTKhrnw23MkC |year=2002 |publisher=Cambridge University Press|isbn=978-0-521-52440-7 |pages=3–5, 45–46}}</ref>

[[File:Haeckel Crinoidea.jpg|left|thumb|upright|Stalked crinoid drawn by [[Ernst Haeckel]]]]

The stem of sea lilies is composed of a column of highly porous ossicles which are connected by ligamentary tissue. It attaches to the substrate with a flattened [[holdfast (biology)|holdfast]] or with whorls of jointed, root-like structures known as [[Cirrus (biology)|cirri]]. Further cirri may occur higher up the stem. In crinoids that attach to hard surfaces, the cirri may be robust and curved, resembling birds' feet, but when crinoids live on soft sediment, the cirri may be slender and rod-like. Juvenile feather stars have a stem, but this is later lost, with many species retaining a few cirri at the base of the crown. The majority of living crinoids are free-swimming and have only a [[Vestigiality|vestigial]] stalk. In those deep-sea species that still retain a stalk, it may reach up to {{convert|1|m|ft|0|abbr=on}} in length (although usually much smaller), and fossil species are known with {{convert|20|m|ft|0|abbr=on}} stems.<ref name=Ruppert>{{Cite book |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard S. |last3=Barnes |first3=Robert D. |year=2004 |title=Invertebrate Zoology: A Functional Evolutionary Approach |url=https://archive.org/details/isbn_9780030259821 |url-access=registration |edition=7th |location=Belmont, CA |publisher=Thomson-Brooks/Cole |pages=[https://archive.org/details/isbn_9780030259821/page/916/mode/2up 917–918] |isbn=9780030259821 |oclc=53021401}}</ref>

The theca is [[Symmetry in biology#Pentamerism|pentamerous]] (has five-part symmetry) and is [[Homology (biology)|homologous]] with the body or disc of other echinoderms. The base of the theca is formed from a cup-shaped set of ossicles (bony plates), the [[Calyx (anatomy)|calyx]], while the upper surface is formed by the weakly-calcified [[tegmen]], a membranous disc. The tegmen is divided into five "ambulacral areas", including a deep groove from which the [[tube feet]] project, and five "interambulacral areas" between them. The mouth is near the centre or on the margin of the tegmen, and [[ambulacral]] grooves lead from the base of the arms to the mouth. The [[anus]] is also located on the tegmen, often on a small elevated cone, in an [[Ambulacral|interambulacral]] area. The theca is relatively small and contains the crinoid's digestive organs.<ref name=Ruppert/>

The arms are supported by a series of articulating ossicles similar to those in the stalk. Primitively, crinoids had only five arms, but in most modern forms these are divided into two at ossicle II, giving ten arms in total. In most living species, especially the free-swimming feather stars, the arms branch several more times, producing up to two hundred branches in total. Being jointed, the arms can curl up. They are lined, on either side alternately, by smaller jointed appendages known as "pinnules" which give them their feather-like appearance. Both arms and pinnules have [[tube feet]] along the margins of the ambulacral grooves. The tube feet come in groups of three of different size; they have no suction pads and are used to hold and manipulate food particles. The grooves are equipped with [[Organelle|cilia]] which facilitate feeding by moving the organic particles along the arm and into the mouth.<ref name=Ruppert/>

<gallery style="text-align:center;" mode="packed">
Image:Crinoide vraie.jpg|Stem, theca and arms of a "true" (stalked) crinoid (family [[Isselicrinidae]])
Image:Comasteridae - Oxycomanthus bennetti-001.jpg|''[[Oxycomanthus bennetti]]'' (comatulid)
Image:Lamprometra palmata hgsus03.JPG|Tegmen of a ''[[Lamprometra palmata]]''. The mouth is located at the center of the 5 feeding grooves, and the anus at the top of the column.
Image:Elegant feather star9.jpg|Close-up on the cirri that allow comatulids to walk and attach themselves
Image:Myzostoma fuscomaculatum at Percys Hole detail.jpg|Close-up on the pinnules of a ''[[Tropiometra carinata]]'' (with parasites ''[[Myzostoma fuscomaculatum]]'')
</gallery>

===Feeding===
[[File:Podia of a red feather star.jpg|thumb|upright|Two arms with pinnules and tube feet outstretched]]
Crinoids are passive [[suspension feeder]]s, filtering [[plankton]] and small particles of [[detritus]] from the sea water flowing past them with their feather-like arms. The arms are raised to form a fan-shape which is held perpendicular to the current. Mobile crinoids move to perch on rocks, coral heads or other eminences to maximise their feeding opportunities. The food particles are caught by the primary (longest) tube feet, which are fully extended and held erect from the pinnules, forming a food-trapping mesh, while the secondary and tertiary tube feet are involved in manipulating anything encountered.<ref name=Ruppert/>

The tube feet are covered with sticky [[mucus]] that traps any particles which come in contact. Once they have caught a particle of food, the tube feet flick it into the [[ambulacral]] groove, where the cilia propel the mucus and food particles towards the mouth. Lappets at the side of the groove help keep the mucus stream in place. The total length of the food-trapping surface may be very large; the 56 arms of a [[Metacrinus rotundus|Japanese sea lily]] with  {{convert|24|cm|in|0|abbr=on}} arms, have a total length of {{convert|80|m|ft|-1|abbr=on}} including the pinnules. Generally speaking, crinoids living in environments with relatively little plankton have longer and more highly branched arms than those living in food-rich environments.<ref name=Ruppert/>

The mouth descends into a short [[oesophagus]]. There is no true stomach, so the oesophagus connects directly to the [[intestine]], which runs in a single loop right around the inside of the calyx. The intestine often includes numerous [[Diverticulum|diverticulae]], some of which may be long or branched. The end of the intestine opens into a short muscular [[rectum]]. This ascends towards the [[anus]], which projects from a small conical protuberance at the edge of the tegmen. Faecal matter is formed into large, mucous-cemented pellets which fall onto the tegmen and thence the substrate.<ref name=Ruppert/>

=== Predation ===
Specimens of the sea urchin ''[[Calocidaris micans]]'' found in the vicinity of the crinoid ''[[Endoxocrinus parrae]]'', have been shown to contain large quantities of stem portions in their guts. These consist of articulated ossicles with soft tissue, whereas the local sediment contained only disarticulated ossicles without soft tissue. This makes it highly likely that these sea urchins are [[Predation|predators]] of the crinoids, and that the crinoids flee, offering part of their stem in the process.<ref>{{cite journal |doi=10.1666/07031.1 |title=Urchins in the meadow: Paleobiological and evolutionary implications of cidaroid predation on crinoids |journal=Paleobiology |volume=34 |issue=1 |pages=22–34 |year=2008 |last1=Baumiller |first1=Tomasz K. |last2=Mooi |first2=Rich |last3=Messing |first3=Charles G. |s2cid=85647638 |jstor=20445573|bibcode=2008Pbio...34...22B }}</ref>

Various crinoid fossils hint at possible prehistoric predators. [[Coprolite]]s of both fish and [[cephalopod]]s have been found containing ossicles of various crinoids, such as the pelagic crinoid ''[[Saccocoma]]'', from the [[Jurassic]] [[Lagerstätte|lagerstatten]] [[Solnhofen]],<ref name="Hess">{{cite book |first=Hans |last=Hess |chapter=Upper Jurassic Solnhofen Plattenkalk of Bavaria, German |chapter-url=https://books.google.com/books?id=TTKhrnw23MkC&pg=PA216 |pages=216–24 |editor1-first=Carlton E. |editor1-last=Brett |editor2-first=William I. |editor2-last=Ausich |editor3-first=Michael J. |editor3-last=Simms |year=2003 |title=Fossil Crinoids |publisher=Cambridge University Press |isbn=978-0-521-52440-7}}</ref> while damaged crinoid stems with bite marks matching the toothplates of [[Coccosteidae|coccosteid]] [[placoderms]] have been found in Late [[Devonian]] [[Poland]].<ref>{{cite journal |doi=10.1127/0077-7749/2010/0111 |title=Inferred placoderm bite marks on Devonian crinoids from Poland |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=259 |pages=105–12 |year=2011 |last1=Gorzelak |first1=Przemys Law |last2=Rakowicz |first2=Lukasz |last3=Salamon |first3=Mariusz A. |last4=Szrek |first4=Piotr}}</ref> The calyxes of several Devonian to [[Carboniferous]]-aged crinoids have the shells of a snail, ''[[Platyceras]]'', intimately associated with them.<ref>{{cite journal |last1=Brett |first1=Carlton E. |first2=Sally E. |last2=Walker |title=Predators and predation in Paleozoic marine environments |journal=Paleontological Society Papers |volume=8 |year=2002 |pages=93–118 |url=http://www.yale.edu/ypmip/predation/Chapter_05.pdf |access-date=2014-04-06 |archive-url=https://web.archive.org/web/20120813070821/http://www.yale.edu/ypmip/predation/Chapter_05.pdf |archive-date=2012-08-13 |url-status=dead |doi=10.1017/S1089332600001078 }}</ref> Some have the snail situated over the anus, suggesting that ''Platyceras'' was a [[Coprophagia|coprophagous]] commensal, while others have the animal directly situated over a borehole, suggesting a more pernicious relationship.<ref>{{cite journal |hdl=2027.42/75509 |title=Infestation of Middle Devonian (Givetian) camerate crinoids by platyceratid gastropods and its implications for the nature of their biotic interaction |journal=Lethaia |volume=36 |issue=2 |pages=71–82 |year=2003 |last1=Gahn |first1=Forest J. |last2=Baumiller |first2=Tomasz K. |doi=10.1080/00241160310003072|bibcode=2003Letha..36...71G |url=https://deepblue.lib.umich.edu/bitstream/2027.42/75509/1/00241160310003072.pdf |hdl-access=free }}</ref>

===Water vascular system===
Like other echinoderms, crinoids possess a [[water vascular system]] that maintains [[hydraulic]] pressure in the tube feet. This is not connected to external sea water via a [[madreporite]], as in other echinoderms, but only connected through a large number of pores to the [[coelom]] (body cavity). The main fluid reservoir is the muscular-walled ring canal which is connected to the coelom by stone canals lined with calcareous material. The coelom is divided into a number of interconnecting spaces by [[Mesentery (zoology)|mesenteries]]. It surrounds the viscera in the disc and has branches within the stalk and arms, with smaller branches extending into the pinnules. It is the contraction of the ring canal that extends the tube feet. Three narrow branches of the coelom enter each arm, two on the oral side and one aborally, and pinnules. The action of cilia cause there to be a slow flow of fluid (1mm per second) in these canals, outward in the oral branches and inward in the aboral ones, and this is the main means of transport of nutrients and waste products. There is no heart and separate circulatory system but at the base of the disc there is a large blood vessel known as the axial organ, containing some slender blind-ended tubes of unknown function, which extends into the stalk.<ref name=Ruppert/>

These various fluid-filled spaces, in addition to transporting nutrients around the body, also function as both a respiratory and an excretory system. Oxygen is absorbed primarily through the tube feet, which are the most thin-walled parts of the body, with further gas exchange taking place over the large surface area of the arms. There are no specialised organs for excretion while waste is collected by [[phagocyte|phagocytic]] coelomocytes.<ref name=Ruppert/>

===Nervous system===
The crinoid nervous system is divided into three parts, with numerous connections between them. The oral or uppermost portion is the only one [[homology (biology)|homologous]] with the nervous systems of other echinoderms. It consists of a central nerve ring surrounding the mouth, and radial nerves branching into the arms and is sensory in function. Below this lies an intermediate nerve ring, giving off radial nerves supplying the arms and pinnules. These nerves are motor in nature, and control the musculature of the tube feet. The third portion of the nervous system lies aborally, and is responsible for the flexing and movement actions of the arms, pinnules and cirri. This is centred on a mass of neural tissue near the base of the calyx, and provides a single nerve to each arm and a number of nerves to the stalk.<ref name=Ruppert/>

===Reproduction and life cycle===
Crinoids are [[Dioecy|dioecious]], with individuals being either male or female. In most species, the [[gonad]]s are located in the pinnules but in a few, they are located in the arms. Not all the pinnules are reproductive, just those closest to the crown. The [[gamete]]s are produced in genital canals enclosed in genital coeloms. The pinnules eventually rupture to release the [[sperm]] and [[ovum|eggs]] into the surrounding sea water. In certain genera, such as ''[[Antedon]]'', the fertilised eggs are cemented to the arms with secretions from epidermal glands; in others, especially cold water species from Antarctica, the eggs are [[Egg incubation|brooded]] in specialised sacs on the arms or pinnules.<ref name=Ruppert/>

The fertilised eggs hatch to release free-swimming [[Echinoderm#Larval development|vitellaria larvae]]. The bilaterally symmetrical larva is barrel-shaped with rings of [[Cilium|cilia]] running round the body, and a tuft of sensory hairs at the upper pole. While both feeding (planktotrophic) and non-feeding (lecithotrophic) larvae exist among the four other extant echinoderm classes, all present day crinoids appear to be descendants from a surviving clade that went through a [[Population bottleneck|bottleneck]] after the [[Permian–Triassic extinction event|Permian extinction]], at that time losing the feeding larval stage.<ref>{{cite journal |doi=10.1038/sj.hdy.6800866 |pmid=16850040 |title=The active evolutionary lives of echinoderm larvae |journal=Heredity |volume=97 |issue=3 |pages=244–52 |year=2006 |last1=Raff |first1=R A |last2=Byrne |first2=M|doi-access=free }}</ref> The larva's free-swimming period lasts for only a few days before it settles on the bottom and attaches itself to the underlying surface using an adhesive gland on its underside. The larva then undergoes an extended period of [[metamorphosis|metamorphoses]] into a stalked [[Juvenile (organism)|juvenile]], becoming radially symmetric in the process. Even the free-swimming feather stars go through this stage, with the adult eventually breaking away from the stalk.<ref name=Ruppert/>

====Regeneration====
Crinoids are not capable of clonal reproduction as are some [[starfish]] and [[brittle star]]s, but are capable of regenerating lost body parts. Arms torn off by predators or damaged by adverse environmental conditions can regrow, and even the [[Organ (biology)|visceral mass]] can regenerate over the course of a few weeks.<ref name=Ruppert/> The stalk's uppermost segment and the basal plates have the capacity to regenerate the entire crown. Nutrients and other components from the stalk, especially the upper 5 cm, are used in crown regeneration.<ref name=AmemiyaOli>{{cite journal |last1=Amemiya |first1=Shonan |last2=Oji |first2=Tatsuo |title=Regeneration in sea lilies |journal=Nature |date=June 1992 |volume=357 |issue=6379 |page=546-547 |doi=10.1038/357546a0 |bibcode=1992Natur.357..546A |url=https://doi.org/10.1038/357546a0 |language=en |issn=1476-4687}}</ref>

Crinoids have been able to regenerate parts since Paleozoic times.<ref name=AmemiyaOli />  These regenerative abilities may be vital in surviving attacks by predatory fish.<ref name=Ruppert/>

==Locomotion==
[[File:Crinoid and comatule.jpg|thumb|upright=1.2|A stalked crinoid (white) and a comatulid (red) in deep sea, showing the differences between these two sister groups]]

Most modern crinoids, i.e., the feather stars, are free-moving and lack a stem as adults. Examples of fossil crinoids that have been interpreted as free-swimming include ''Marsupites'', ''Saccocoma'' and ''Uintacrinus''.<ref>{{cite web |url=https://www.fossilera.com/pages/about-crinoids |title=About Crinoids |publisher=FossilEra |access-date=15 March 2019}}</ref> In general, crinoids move to new locations by crawling, using the cirri as legs. Such a movement may be induced in relation to a change in current direction, the need to climb to an elevated perch to feed, or because of an agonistic behaviour by an encountered individual.<ref name=Shaw>{{cite journal |author1=Shaw, G.D. |author2=Fontaine, A.R.  |year=2011 |title=The locomotion of the comatulid ''Florometra serratissima'' (Echinodermata: Crinoidea) and its adaptive significance |journal=Canadian Journal of Zoology |volume=68 |issue=5 |pages=942–950 |doi=10.1139/z90-135 }}</ref> Crinoids can also swim. They do this by co-ordinated, repeated sequential movements of the arms in three groups. At first the direction of travel is upwards but soon becomes horizontal, travelling at about {{convert|7|cm|in|1|abbr=on}} per second with the oral surface in front. Swimming usually takes place as short bursts of activity lasting up to half a minute, and in the comatulid ''[[Florometra serratissima]]'' at least, only takes place after mechanical stimulation or as an escape response evoked by a predator.<ref name=Shaw/>

In 2005, a stalked crinoid was recorded pulling itself along the sea floor off the [[Grand Bahama|Grand Bahama Island]]. While it has been known that stalked crinoids could move, before this recording the fastest motion known for a stalked crinoid was {{convert|0.6|m|ft|0|abbr=off}} per hour. The 2005 recording showed one of these moving across the seabed at the much faster rate of {{convert|4|to|5|cm|in|1|abbr=on}} per second, or {{convert|144|to|180|m|ft|0|abbr=on}} per hour.<ref>{{cite conference |last1=Baumiller |first1=Tomasz K. |last2=Messing |first2=Charles G. |title=Crawling In Stalked Crinoids: In Situ Observations, Functional Morphology, and Implications for Paleozoic Taxa |book-title=Geological Society of America Abstracts with Programs |volume=37 |issue=7 |date=6 October 2005 |page=62 |url=https://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96883.htm |access-date=6 April 2014 |archive-url=https://web.archive.org/web/20140407090700/https://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96883.htm |archive-date=7 April 2014 |url-status=dead }}</ref>

==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.

== Taxonomy ==
[[File:Colorful crinoids at shallow waters of Gili Lawa Laut.JPG|thumb|upright|Colorful crinoids in shallow waters in Indonesia]]
[[File:Multiple crinoids occupying the reef of Nusa Kode Island.JPG|thumb|upright|Multiple crinoids on a reef in Indonesia]]
[[File:Pretty crinoid, trailblazer, wakatobi, 2018 (30873153967).jpg|thumb|Crinoid at [[Wakatobi National Park]], 2018]]

Crinoidea has been accepted as a distinct [[clade]] of echinoderms since the definition of the group by Miller in 1821.<ref name=Ausich2015/> It includes many extinct orders as well as four closely related living orders ([[Comatulida]], [[Cyrtocrinida]], [[Hyocrinida]], and [[Isocrinida]]), which are part of the subgroup [[Articulata (Crinoidea)|Articulata]]. Living articulates comprise around 540 species.

* Class Crinoidea
** †[[Protocrinoidea]] (''[[incertae sedis]]'')
** Subclass †[[Camerata (crinoid)|Camerata]]
*** Order †[[Diplobathrida]]
*** Order †[[Monobathrida]]
** Subclass [[Pentacrinoidea]]
*** Parvclass †[[Disparida]]
**** Order †[[Eustenocrinida]]
**** Order †[[Maennilicrinida]]
**** Order †[[Tetragonocrinida]]
**** Order †[[Calceocrinida]]
*** Parvclass [[Cladida]]
**** Superorder †[[Porocrinoidea]]
***** Order †[[Hybocrinida]]
***** Order †[[Porocrinida]]
**** Superorder †[[Flexibilia]]
***** Order †[[Sagenocrinida]]
***** Order †[[Taxocrinida]]
**** Magnorder [[Eucladida]]
***** †[[Ampelocrinida]] (''[[incertae sedis]]'')
***** Superorder †[[Cyathoformes]]
***** Superorder [[Articulata (Crinoidea)|Articulata]]
****** Order †[[Encrinida]]
****** Order †[[Holocrinida]]
****** Order †[[Millericrinida]]
****** Order †[[Roveacrinida]]
****** Order †[[Uintacrinida]]
****** Order [[Comatulida]]
****** Order [[Cyrtocrinida]]
****** Order [[Hyocrinida]]
****** Order [[Isocrinida]]

===Phylogeny===

The [[phylogeny]], geologic history, and classification of the [[Crinoidea]] was discussed by Wright et al. (2017).<ref>{{cite journal |author1=Wright, David F. |author2=Ausich, William I. |author3=Cole, Selina R. |author4=Peter, Mark E. |author5=Rhenberg, Elizabeth C. | year=2017 |title= Phylogenetic taxonomy and classification of the Crinoidea (Echinodermata) |journal= Journal of Paleontology |volume=91 |issue= 4|pages= 829–846|doi=10.1017/jpa.2016.142|doi-access=free |bibcode=2017JPal...91..829W }}</ref> These authors presented new phylogeny-based and rank-based classifications based on results of recent phylogenetic analyses.<ref name=Ausich2015>{{cite journal |author1=Ausich, William I. |author2=Kammer, Thomas W. |author3=Rhenberg, Elizabeth C. |author4=Wright, David F. |year=2015 |title= Early phylogeny of crinoids within the pelmatozoan clade |journal= Palaeontology |volume= 58 |issue= 6 |pages= 937–952 |doi=10.1111/pala.12204|doi-access=free |bibcode=2015Palgy..58..937A }}</ref><ref>{{cite journal |author=Wright, David F. | year=2017 |title= Bayesian estimation of fossil phylogenies and the evolution of early to middle Paleozoic crinoids (Echinodermata) |journal= Journal of Paleontology |volume= 91 |issue= 4|pages= 799–814|doi=10.1017/jpa.2016.141|doi-access= free | bibcode=2017JPal...91..799W }}</ref><ref>{{cite journal |author=Cole, Selina R. | year=2017 |title= Phylogeny and morphologic evolution of the Ordovician Camerata (Class Crinoidea, Phylum Echinodermata) |journal= Journal of Paleontology |volume= 91 |issue= 4|pages= 815–828|doi=10.1017/jpa.2016.137|doi-access= free | bibcode=2017JPal...91..815C }}</ref><ref>{{cite journal |author1=Rouse, Greg W. |author2=Jermiin, Lars S. |author3=Wilson, Nerida G. |author4=Eeckhaut, Igor |author5=Lanterbecq, Deborah |author6=Oji, Tatsuo |author7=Young, Craig M. |author8=Browning, Teena |author9=Cisternas, Paula |author10=Helgen, Lauren E. |author11=Stuckey, Michelle |author12=Messing, Charles G. |year=2013 |title= Fixed, free, and fixed: the fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian-Triassic origin |journal= Molecular Phylogenetics and Evolution |volume= 66 |issue= 6|pages= 161–181 |doi=10.1016/j.ympev.2012.09.018|pmid=23063883 |bibcode=2013MolPE..66..161R }}</ref> Their rank-based classification of crinoid higher taxa (down to Order), not fully resolved and with numerous groups ''[[incertae sedis]]'' (of uncertain placement), is illustrated in the [[cladogram]].

{{clade
|label1='''Crinoidea'''
|1={{clade
   |1=† [[Protocrinoidea]] (''[[incertae sedis]]'')
   |label2=† [[Camerata (crinoid)|Camerata]]
   |2={{clade
      |label1=† [[Eucamerata]]
      |1={{clade 
         |1=† [[Diplobathrida]] 
         |2=† [[Monobathrida]] [[File:Actinocrinus indiana 330m.jpg|50px]]
         }}
      }}
   |label3=[[Pentacrinoidea]]
   |3={{clade
      |label1=[[Inadunata]]
      |1={{clade
         |label1=[[Disparida]]
         |1={{clade
            |1=[[Eustenocrinida]] 
            |2=[[Maennilicrinida]] 
            |3=[[Tetragonocrinida]] 
            |4=[[Calceocrinida]]
            |5='[[Homocrinida]]'  (''[[incertae sedis]]'')
            |6='[[Myelodactyla]]' (''[[incertae sedis]]'')
            |7='[[Pisocrinoidea]]' (''[[incertae sedis]]'')
            }}
         |label2=[[Cladida]]
         |2={{clade
            |label1=[[Porocrinoidea]]
            |1={{clade
               |1=[[Porocrinida]]
               |2=[[Hybocrinida]]
               }}
            |label2=[[Flexibilia]]
            |2={{clade
               |1=[[Taxocrinida]] [[File:Taxocrinus telleri.jpg|60px]]
               |2=[[Sagenocrinida]] 
               }}
            |label3=[[Eucladida]]
            |3={{clade
               |label1=[[Cyathoformes]]
               |1={{clade
                  |1='[[Cyathocrinida]]' (''[[incertae sedis]]'')
                  |2='[[Dendrocrinida]]'  (''[[incertae sedis]]'')
                  |3='[[Poteriocrinida]]' (''[[incertae sedis]]'')
                  |4=† '[[Ampelocrinida]]'  (''[[incertae sedis]]'')
                  }}
               |label2=[[Articulata (Crinoidea)|Articulata]] 
               |2={{clade
                  |1=[[Holocrinida]] 
                  |2=† [[Encrinida]] [[File:Encrinus liliiformis.JPG|70px]]
                  |3=[[Millericrinida]] [[File:Seirocrinus subsingularis, view 2, Jurassic, Hlzmaden Black Shale Formation, Holzmaden, Germany.JPG|60px]]
                  |4=[[Uintacrinida]] 
                  |5=[[Roveacrinida]] 
                  |6=[[Cyrtocrinida]] [[File:Holopus.jpg|70px]] 
                  |7=[[Hyocrinida]] [[File:Hyocrinus sp.jpg|60px]]
                  |8=[[Isocrinida]] [[File:Neocrinus decorus.jpg|60px]]
                  |9=[[Comatulida]] [[File:Comasteridae - Oxycomanthus bennetti-003.jpg|60px]]
                  }}
               }}
            }}
         }}
      }}
   }}
}}
<!-- SPARES - (THESE ORDERS ALREADY HAVE IMAGES - WILL BE USEFUL IF WE GO DOWN TO FAMILIES LATER)
[[File:Antedon mediterranea (Lamarck, 1816).jpg|70px]] Antedonidae COMATULIDA
[[File:Sarametra triserialis.jpg|70px]]  |[[Zenometridae]] COMATULIDA
[[File:Cenometra bella Maldives.JPG|70px]]  |[[Colobometridae]] COMATULIDA
[[File:Himerometridae - Himerometra robustipinna-001.jpg|70px]] |[[Himerometridae]] COMATULIDA
[[File:Stephanometra indica, Lizard.jpeg|70px]] |[[Mariametridae]] COMATULIDA
[[File:Ptilometra australis Passion Flower feather star.jpg|70px]]  |[[Ptilometridae]] COMATULIDA
[[File:Elegant feather star at Glencairn Fan Gardens P9078452.JPG|70px]]  |[[Tropiometridae]] COMATULIDA
[[File:Guillecrinus neocaledonicus.jpg|70px]] |[[Guillecrinidae]] INCERTAE SEDIS 
[[File:Proisocrinus ruberrimus.jpg|70px]] |[[Proisocrinidae]] ANOTHER ISOCRINIDA
[[File:Metacrinus rotundus by OpenCage.JPG|70px]] |[[Isselicrinidae]] ISOCRINIDA
[[File:Vivid Crinoids.jpg|70px]]  |[[Charitometridae]] ANOTHER COMATULIDA
-->

==  In culture ==
Fossilised crinoid columnal segments extracted from [[limestone]] quarried on [[Lindisfarne]], or found washed up along the foreshore, were threaded into [[necklace]]s or [[rosary|rosaries]], and became known as [[St. Cuthbert's beads]] in the [[England in the Middle Ages|Middle Ages]].<ref>{{cite journal |author1=Lane, N. Gary |author2=Ausich, William I.  |year=2001 |title=The Legend of St Cuthbert's Beads: A Palaeontological and Geological Perspective  |journal=Folklore |volume=112 |issue=1 |pages=65–73 |jstor=1260865 }}</ref> Similarly, in the Midwestern United States, fossilized segments of the columns of crinoids are sometimes known as [[Indian bead]]s.<ref>{{cite web  |title = Identifying Unknown Fossils (by their shape) |url = http://www.uky.edu/KGS/fossils/fossilid.htm |publisher = Kentucky Geological Survey / University of Kentucky |access-date  = 21 June 2009 }}</ref> A species of crinoid, ''[[Delocrinus|Eperisocrinus missouriensis]]'', is the [[List of U.S. state fossils|state fossil]] of [[Missouri]].<ref>{{cite web |url=http://www.sos.mo.gov/symbols/symbols.asp?symbol=fossil |title=Missouri's State Fossil |publisher=Office of the Secretary of State, Missouri|access-date  = 31 March 2019}}</ref>  The aliens in the movie franchise ''[[Alien (franchise)|Alien]]'' were inspired by crinoids.<ref>{{cite news |last1=Bressan |first1=David |title=The Fossils That Inspired 'Alien' |url=https://www.forbes.com/sites/davidbressan/2019/04/26/the-fossil-that-inspired-alien/?sh=3cb1f9a15d56 |access-date=1 February 2024 |work=[[Forbes]] |date=26 April 2019 |language=en}}</ref>

== Fossil crinoid gallery ==
<gallery class="center" widths="180">
File:Crushed crinoid stems from the Jurassic, Iran.jpg|Crushed crinoid stems from Shamshak Formation, Jurassic, Iran
File:Fossile-seelilie.jpg|Fossil from Germany showing the stem, calyx, and arms with pinnules
File:Crinoids iowa 330m.jpg|330 million year old crinoid fossils from [[Iowa]]
File:OrdCrinoidHoldfasts.jpg|Crinoid holdfasts and [[bryozoa]]ns on an Upper [[Ordovician]] cobble from northern [[Kentucky]]
File:Seirocrinus subangularis (fossil Crinoid).jpg|''[[Seirocrinus subangularis]]'' from the Early [[Jurassic]] [[Posidonia Shale]] at [[Holzmaden]], Germany
File:Isocrinus nicoleti Encrinite Mt Carmel.jpg|Crinoid columnals (''[[Isocrinus nicoleti]]'') from the Middle [[Jurassic]] [[Carmel Formation]] at Mount Carmel Junction, [[Utah]]
File:CrinoidHoldfastRoots.JPG|Root-like crinoid holdfast from the Upper Ordovician, southern [[Ohio]]
File:Crinoid internal mold lumen.jpg|Internal mold of crinoid stem lumen (and external mold of stem) from Lower Carboniferous, Ohio
File:Seirocrinus subsingularis, view 2, Jurassic, Hlzmaden Black Shale Formation, Holzmaden, Germany.JPG|Fossils of ''[[Seirocrinus subsingularis]]'' from the Jurassic Holzmaden Black Shale Formation, Germany
File:Crinoid-MCG 1219-P4150562-black.jpg|Crinoid
</gallery>

==See Also==
*[[Echinobase]], a database that contains information about various echinoderms, including a crinoid species.

==References==
{{Reflist}}

==External links==
{{Commons category}}
{{Wikispecies}}
* {{Cite web |last1=Messing |first1=Charles |title=Sea Star on a Stick: Introducing Crinoids |url=https://vimeo.com/502443533 |publisher=Vimeo }}
* [https://libguides.nova.edu/crinoids/home Charles Messing's Crinoid Pages]

{{Taxonbar|from=Q33666}}
{{Authority control}}

[[Category:Crinoidea]]
[[Category:Extant Ordovician first appearances]]
[[Category:Paleozoic invertebrates]]