Crinoid

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Crinoids
Temporal range: Ordovician–recent [1]
Crinoid on the reef of Batu Moncho Island.JPG
Crinoid on the reef of Batu Moncho Island, Indonesia
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Subphylum: Crinozoa
Class: Crinoidea
Miller, 1821 [2]
Major groups

Crinoids are marine invertebrates that make up the 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 [3] [4] or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. [5] They live in both shallow water [6] and in depths over 9,000 metres (30,000 ft). [7]

Contents

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 planktonic particles from the water. At some stage in their lives, most crinoids have a short stem used to attach themselves to the substrate, but many live attached only as juveniles and become free-swimming as adults.

There are only about 700 living species of crinoid, [8] but the class was much more abundant and diverse in the past. Some thick limestone beds dating to the mid-Paleozoic era to Jurassic period are almost entirely made up of disarticulated crinoid fragments. [9] [10] [11]

Etymology

The name "Crinoidea" comes from the Ancient Greek word κρίνον (krínon), "a lily", with the suffix –oid meaning "like". [12] [13]

Morphology

Anatomy of a stalked crinoid Crinoid anatomy.png
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 (upper) surface the oral surface, unlike in the other echinoderm groups such as the sea urchins, starfish and brittle stars where the mouth is on the underside. [14] The numerous calcareous plates make up the bulk of the crinoid, with only a small percentage of soft tissue. These ossicles fossilise well and there are beds of limestone dating from the Lower Carboniferous around Clitheroe, England, formed almost exclusively from a diverse fauna of crinoid fossils. [15]

Stalked crinoid drawn by Ernst Haeckel Haeckel Crinoidea.jpg
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 or with whorls of jointed, root-like structures known as 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 vestigial stalk. In those deep-sea species that still retain a stalk, it may reach up to 1 m (3 ft) in length (although usually much smaller), and fossil species are known with 20 m (66 ft) stems, [5] the largest recorded crinoid having a stem 40 m (130 ft) in length. [16]

The theca is pentamerous (has five-part symmetry) and is 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, 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 interambulacral area. The theca is relatively small and contains the crinoid's digestive organs. [5]

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 cilia which facilitate feeding by moving the organic particles along the arm and into the mouth. [5]

Feeding

Two arms with pinnules and tube feet outstretched Podia of a red feather star.jpg
Two arms with pinnules and tube feet outstretched

Crinoids are passive suspension feeders, 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. [5]

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 Japanese sea lily with 24 cm (9 in) arms, have a total length of 80 m (260 ft) 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. [5]

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 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. [5]

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 predators of the crinoids, and that the crinoids flee, offering part of their stem in the process. [17]

Various crinoid fossils hint at possible prehistoric predators. Coprolites of both fish and cephalopods have been found containing ossicles of various crinoids, such as the pelagic crinoid Saccocoma , from the Jurassic lagerstatten Solnhofen, [18] while damaged crinoid stems with bite marks matching the toothplates of coccosteid placoderms have been found in Late Devonian Poland. [19] The calyxes of several Devonian to Carboniferous-aged crinoids have the shells of a snail, Platyceras , intimately associated with them. [20] Some have the snail situated over the anus, suggesting that Platyceras was a coprophagous commensal, while others have the animal directly situated over a borehole, suggesting a more pernicious relationship. [21]

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 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. [5]

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 phagocytic coelomocytes. [5]

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 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. [5]

Reproduction and life cycle

Crinoids are dioecious, with individuals being either male or female. In most species, the gonads 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 gametes are produced in genital canals enclosed in genital coeloms. The pinnules eventually rupture to release the sperm and 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 brooded in specialised sacs on the arms or pinnules. [5]

The fertilised eggs hatch to release free-swimming vitellaria larvae. The bilaterally symmetrical larva is barrel-shaped with rings of 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 bottleneck after the Permian extinction, at that time losing the feeding larval stage. [22] 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 metamorphoses into a stalked 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. [5]

Regeneration

Crinoids are not capable of clonal reproduction as are some starfish and brittle stars, but are capable of regenerating lost body parts. Arms torn off by predators or damaged by adverse environmental conditions can regrow, and even the visceral mass can regenerate over the course of a few weeks. [5] 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. [23]

Crinoids have been able to regenerate parts since Paleozoic times. [23] These regenerative abilities may be vital in surviving attacks by predatory fish. [5]

Locomotion

A stalked crinoid (white) and a comatulid (red) in deep sea, showing the differences between these two sister groups Crinoid and comatule.jpg
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. [24] 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. [25] 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 7 cm (2.8 in) 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. [25]

In 2005, a stalked crinoid was recorded pulling itself along the sea floor off the 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 0.6 metres (2 feet) per hour. The 2005 recording showed one of these moving across the seabed at the much faster rate of 4 to 5 cm (1.6 to 2.0 in) per second, or 144 to 180 m (472 to 591 ft) per hour. [26]

Evolution

Origins

Agaricocrinus americanus, a fossil crinoid from the Carboniferous of Indiana Agaricocrinus americanus Carboniferous Indiana.jpg
Agaricocrinus americanus , a fossil crinoid from the Carboniferous of Indiana
Middle Jurassic (Callovian) Apiocrinites crinoid pluricolumnals from the Matmor Formation in southern Israel JurassicCrinoidsIsrael.JPG
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 blastozoans (the eocrinoids and their derived descendants, the blastoids and the cystoids), whereas the most popular alternative suggests that the crinoids split early from among the edrioasteroids. [27] 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. [27]

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. [28] At that time, the Echinodermata included twenty taxa of 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. [5]

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). [29] 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. [30] This radiation occurred somewhat earlier than the Mesozoic marine revolution, possibly because it was mainly prompted by increases in benthic predation, specifically of echinoids. [31] There then followed a selective mass extinction at the end of the Permian period, during which all blastoids and most crinoids became extinct. [29] 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. [29]

Fossils

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. The largest fossil crinoid on record had a stem 40 m (130 ft) in length. [16]

In 2012, three geologists reported they had isolated complex organic molecules from 340-million-year-old (Mississippian) fossils of multiple species of crinoids. Identified as "resembl[ing ...] aromatic or polyaromatic quinones", 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. [32]

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 ] Rocks of this nature are called encrinites.

Taxonomy

Colorful crinoids in shallow waters in Indonesia Colorful crinoids at shallow waters of Gili Lawa Laut.JPG
Colorful crinoids in shallow waters in Indonesia
Multiple crinoids on a reef in Indonesia Multiple crinoids occupying the reef of Nusa Kode Island.JPG
Multiple crinoids on a reef in Indonesia
Crinoid at Wakatobi National Park, 2018 Pretty crinoid, trailblazer, wakatobi, 2018 (30873153967).jpg
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. [33] 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. Living articulates comprise around 540 species.

Phylogeny

The phylogeny, geologic history, and classification of the Crinoidea was discussed by Wright et al. (2017). [34] These authors presented new phylogeny-based and rank-based classifications based on results of recent phylogenetic analyses. [33] [35] [36] [37] 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.

Crinoidea

In culture

Fossilised crinoid columnal segments extracted from limestone quarried on Lindisfarne, or found washed up along the foreshore, were threaded into necklaces or rosaries, and became known as St. Cuthbert's beads in the Middle Ages. [38] Similarly, in the Midwestern United States, fossilized segments of the columns of crinoids are sometimes known as Indian beads. [39] A species of crinoid, Eperisocrinus missouriensis , is the state fossil of Missouri. [40] The aliens in the movie franchise Alien were inspired by crinoids. [41]

See Also

Related Research Articles

<span class="mw-page-title-main">Echinoderm</span> Exclusively marine phylum of animals with generally 5-point radial symmetry

An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.

<span class="mw-page-title-main">Articulata (Crinoidea)</span> Subclass of crinoids

Articulata are a subclass or superorder within the class Crinoidea, including all living crinoid species. They are commonly known as sea lilies or feather stars. The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an entoneural system. Articulata first appeared in the fossil record during the Triassic period although other, now extinct crinoid groups, originated in the Ordovician.

<i>Pentacrinites</i> Extinct genus of crinoids

Pentacrinites is an extinct genus of crinoids that lived from the Hettangian to the Bathonian of Asia, Europe, North America, and New Zealand. Their stems are pentagonal to star-shaped in cross-section and are the most commonly preserved parts. Pentacrinites are commonly found in the Pentacrinites Bed of the Early Jurassic of Lyme Regis, Dorset, England. Pentacrinites can be recognized by the extensions all around the stem, which are long, unbranching, and of increasing length further down, the very small cup and 5 long freely branching arms.

<span class="mw-page-title-main">Homalozoa</span> Extinct historic group of marine invertebrates

Homalozoa is an obsolete extinct subphylum of Paleozoic era echinoderms, prehistoric marine invertebrates. They are also referred to as carpoids.

<i>Antedon</i> Genus of crinoids

Antedon is a genus of sessile, stemless crinoids. The genus first appeared in the fossil record in the Cretaceous period.

<i>Antedon bifida</i> Species of crinoid

Antedon bifida is a species of crinoid in the family Antedonidae commonly known as the rosy feather star. It is found in north west Europe.

<i>Encrinus</i> Extinct genus of crinoids

Encrinus is an extinct genus of crinoids, and "one of the most famous". It lived during the Late Silurian-Late Triassic, and its fossils have been found in Europe.

<span class="mw-page-title-main">Comatulida</span> Order of crinoids

Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.

<i>Metacrinus rotundus</i> Species of crinoid

Metacrinus rotundus, the Japanese sea lily, is a species of stalked crinoid in the family Isselicrinidae. It is a species found off the west coast of Japan, near the edge of the continental shelf at a depth of around 100 to 150 metres deep. This is the shallowest-living species among the extant stalked crinoids.

<span class="mw-page-title-main">Bourgueticrinida</span> Extinct order of crinoids

Bourgueticrinida is an order of crinoids that typically live deep in the ocean. Members of this order are attached to the seabed by a slender stalk and are known as sea lilies. While other groups of crinoids flourished during the Permian, bourgueticrinids along with other extant orders did not appear until the Triassic, following a mass extinction event in which nearly all crinoids died out.

<i>Cenocrinus</i> Genus of crinoids

Cenocrinus is a monotypic genus of stalked crinoids in the family Isselicrinidae. The great West Indian sea lily is the only species in the genus and is found in deep waters in the Caribbean Sea and Gulf of Mexico.

<span class="mw-page-title-main">Camerata (crinoid)</span> Extinct subclass of crinoids

The Camerata or camerate crinoids are an extinct subclass of Paleozoic stalked crinoids. They were some of the earliest crinoids to originate during the Early Ordovician, reached their maximum diversity during the Mississippian, and became extinct during the Permian–Triassic extinction event. Camerates are the sister group of Pentacrinoidea, which contains all other crinoids. The two largest camerate subgroups are the orders Diplobathrida and Monobathrida.

<i>Leptometra celtica</i> Species of crinoid

Leptometra celtica is a marine invertebrate and species of crinoid or feather star of the Leptometra genus in the family Antedonidae. It is found in the Atlantic Ocean around the coasts of north west Europe. The presence of L. celtica and L. phalangium is considered to be a good indication of nearby shelf breaks, general bottom currents, and areas of high gross productivity as they are suspension-feeders, hence their proliferation in productive environments.

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018.

<i>Endoxocrinus parrae</i> Species of crinoid

Endoxocrinus parrae is a species of stalked crinoids of the family Isselicrinidae. It is the most commonly found isocrinine species in west Atlantic Ocean.

<i>Promachocrinus kerguelensis</i> Species of crinoids

Promachocrinus kerguelensis is a species of free-swimming, stemless crinoids. It was the only member of its genus until several species were discovered in 2023. P. keruguelensis a coldwater crinoid which is found in the seas around Antarctica and surrounding island groups, including under the sea ice.

<i>Aporometra wilsoni</i> Species of crinoid

Aporometra wilsoni is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It is found in shallow water around the coasts of southern Australia.

<i>Notocrinus virilis</i> Species of crinoid

Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. A sea snail sometimes parasitizes it.

<i>Cenometra bella</i> Species of crinoid

Cenometra bella is a species of crinoids belonging to the genus Cenometra. They can have up to 30 arms and can be of variable colours but are often characterised by a marked contrast between the extending free-arms and the feathery pinnules. This species clings to its support and moves around by its feet-like cirri.

<span class="mw-page-title-main">Flexibilia</span> Superorder of crinoids

Flexibilia is a superorder of specialized Paleozoic crinoids. They exhibited a conserved body plan and consistent suite of characteristics throughout their long history. Previously considered a subclass with unclear affinities, later investigation determined that flexibles are well-nested within Cladida, a broad group ancestral to living articulate crinoids. The Ordovician cladid Cupulocrinus acts as an intermediate form linking the generalized anatomy of other early cladids with the distinctive anatomy of flexibles, and several studies have considered it to be ancestral to the rest of the group. Although flexibles never reached the same abundance or diversity as many other crinoid groups, they remained a reliable component of crinoid faunas, particularly from the Silurian onwards. Flexible fossils are very rare in the Ordovician, but the Late Ordovician appears to have been an interval of rapid diversification for the group.

References

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  15. ↑ Hess, Hans; Brett, Carlton E.; Ausich, William I.; Simms, Michael J. (2002). Fossil Crinoids. Cambridge University Press. pp. 3–5, 45–46. ISBN   978-0-521-52440-7.
  16. 1 2 Ponsonby, David; Dussart, George (2005). The Anatomy of the Sea. Vancouver: Raincoast Books. p. 129. ISBN   978-0-8118-4633-2.
  17. ↑ Baumiller, Tomasz K.; Mooi, Rich; Messing, Charles G. (2008). "Urchins in the meadow: Paleobiological and evolutionary implications of cidaroid predation on crinoids". Paleobiology. 34 (1): 22–34. Bibcode:2008Pbio...34...22B. doi:10.1666/07031.1. JSTOR   20445573. S2CID   85647638.
  18. ↑ Hess, Hans (2003). "Upper Jurassic Solnhofen Plattenkalk of Bavaria, German". In Brett, Carlton E.; Ausich, William I.; Simms, Michael J. (eds.). Fossil Crinoids. Cambridge University Press. pp. 216–24. ISBN   978-0-521-52440-7.
  19. ↑ Gorzelak, Przemys Law; Rakowicz, Lukasz; Salamon, Mariusz A.; Szrek, Piotr (2011). "Inferred placoderm bite marks on Devonian crinoids from Poland". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 259: 105–12. doi:10.1127/0077-7749/2010/0111.
  20. ↑ Brett, Carlton E.; Walker, Sally E. (2002). "Predators and predation in Paleozoic marine environments" (PDF). Paleontological Society Papers. 8: 93–118. doi:10.1017/S1089332600001078. Archived from the original (PDF) on 2012-08-13. Retrieved 2014-04-06.
  21. ↑ Gahn, Forest J.; Baumiller, Tomasz K. (2003). "Infestation of Middle Devonian (Givetian) camerate crinoids by platyceratid gastropods and its implications for the nature of their biotic interaction" (PDF). Lethaia. 36 (2): 71–82. Bibcode:2003Letha..36...71G. doi:10.1080/00241160310003072. hdl: 2027.42/75509 .
  22. ↑ Raff, R A; Byrne, M (2006). "The active evolutionary lives of echinoderm larvae". Heredity. 97 (3): 244–52. doi: 10.1038/sj.hdy.6800866 . PMID   16850040.
  23. 1 2 Amemiya, Shonan; Oji, Tatsuo (June 1992). "Regeneration in sea lilies". Nature. 357 (6379): 546-547. Bibcode:1992Natur.357..546A. doi:10.1038/357546a0. ISSN   1476-4687.
  24. ↑ "About Crinoids". FossilEra. Retrieved 15 March 2019.
  25. 1 2 Shaw, G.D.; Fontaine, A.R. (2011). "The locomotion of the comatulid Florometra serratissima (Echinodermata: Crinoidea) and its adaptive significance". Canadian Journal of Zoology. 68 (5): 942–950. doi:10.1139/z90-135.
  26. ↑ Baumiller, Tomasz K.; Messing, Charles G. (6 October 2005). "Crawling In Stalked Crinoids: In Situ Observations, Functional Morphology, and Implications for Paleozoic Taxa". Geological Society of America Abstracts with Programs. Vol. 37. p. 62. Archived from the original on 7 April 2014. Retrieved 6 April 2014.
  27. 1 2 Guensburg, Thomas E.; Mooi, Rich; Sprinkle, James; David, Bruno; Lefebvre, Bertrand (2010). "Pelmatozoan arms from the mid-Cambrian of Australia: Bridging the gap between brachioles and brachials? Comment: There is no bridge". Lethaia. 43 (3): 432–440. Bibcode:2010Letha..43..432G. doi:10.1111/j.1502-3931.2010.00220.x.
  28. ↑ Waggoner, Ben (16 January 1995). "Echinodermata: Fossil Record". Introduction to the Echinodermata. Museum of Paleontology: University of California at Berkeley. Retrieved 30 March 2019.
  29. 1 2 3 Foote, Mike (1999). "Morphological diversity in the evolutionary radiation of Paleozoic and post-Paleozoic crinoids". Paleobiology. 25 (sp1): 1–116. doi:10.1666/0094-8373(1999)25[1:MDITER]2.0.CO;2. ISSN   0094-8373. JSTOR   2666042. S2CID   85586709.
  30. ↑ Baumiller, Tomasz K. (2008). "Crinoid Ecological Morphology". Annual Review of Earth and Planetary Sciences. 36: 221–249. Bibcode:2008AREPS..36..221B. doi:10.1146/annurev.earth.36.031207.124116.
  31. ↑ Baumiller, T. K.; Salamon, M. A.; Gorzelak, P.; Mooi, R.; Messing, C. G.; Gahn, F. J. (2010). "Post-Paleozoic crinoid radiation in response to benthic predation preceded the Mesozoic marine revolution". Proceedings of the National Academy of Sciences. 107 (13): 5893–5896. Bibcode:2010PNAS..107.5893B. doi: 10.1073/pnas.0914199107 . JSTOR   25665085. PMC   2851891 . PMID   20231453. INIST   22572914.
  32. ↑ O'Malley, C. E.; Ausich, W. I.; Chin, Y.-P. (2013). "Isolation and characterization of the earliest taxon-specific organic molecules (Mississippian, Crinoidea)". Geology. 41 (3): 347. Bibcode:2013Geo....41..347O. doi:10.1130/G33792.1. 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.
  33. 1 2 Ausich, William I.; Kammer, Thomas W.; Rhenberg, Elizabeth C.; Wright, David F. (2015). "Early phylogeny of crinoids within the pelmatozoan clade". Palaeontology. 58 (6): 937–952. Bibcode:2015Palgy..58..937A. doi: 10.1111/pala.12204 .
  34. ↑ Wright, David F.; Ausich, William I.; Cole, Selina R.; Peter, Mark E.; Rhenberg, Elizabeth C. (2017). "Phylogenetic taxonomy and classification of the Crinoidea (Echinodermata)". Journal of Paleontology. 91 (4): 829–846. Bibcode:2017JPal...91..829W. doi: 10.1017/jpa.2016.142 .
  35. ↑ Wright, David F. (2017). "Bayesian estimation of fossil phylogenies and the evolution of early to middle Paleozoic crinoids (Echinodermata)". Journal of Paleontology. 91 (4): 799–814. Bibcode:2017JPal...91..799W. doi: 10.1017/jpa.2016.141 .
  36. ↑ Cole, Selina R. (2017). "Phylogeny and morphologic evolution of the Ordovician Camerata (Class Crinoidea, Phylum Echinodermata)". Journal of Paleontology. 91 (4): 815–828. Bibcode:2017JPal...91..815C. doi: 10.1017/jpa.2016.137 .
  37. ↑ Rouse, Greg W.; Jermiin, Lars S.; Wilson, Nerida G.; Eeckhaut, Igor; Lanterbecq, Deborah; Oji, Tatsuo; Young, Craig M.; Browning, Teena; Cisternas, Paula; Helgen, Lauren E.; Stuckey, Michelle; Messing, Charles G. (2013). "Fixed, free, and fixed: the fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian-Triassic origin". Molecular Phylogenetics and Evolution. 66 (6): 161–181. Bibcode:2013MolPE..66..161R. doi:10.1016/j.ympev.2012.09.018. PMID   23063883.
  38. ↑ Lane, N. Gary; Ausich, William I. (2001). "The Legend of St Cuthbert's Beads: A Palaeontological and Geological Perspective". Folklore. 112 (1): 65–73. JSTOR   1260865.
  39. ↑ "Identifying Unknown Fossils (by their shape)". Kentucky Geological Survey / University of Kentucky. Retrieved 21 June 2009.
  40. ↑ "Missouri's State Fossil". Office of the Secretary of State, Missouri. Retrieved 31 March 2019.
  41. ↑ Bressan, David (26 April 2019). "The Fossils That Inspired 'Alien'". Forbes . Retrieved 1 February 2024.
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