Articulata (Crinoidea)

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Articulata
Temporal range: Triassic–recent
Ptilometra australis Passion Flower feather star.jpg
A passion flower feather star
( Ptilometra australis )
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Echinodermata
Class: Crinoidea
Subclass: Articulata
Orders

Articulata are a subclass or superorder within the class Crinoidea, including the only living crinoid species. They are commonly known as sea lilies (stalked crinoids) or feather stars (unstalked crinoids). 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. [1]

Contents

Characteristics

Articulata exhibit pentamerous symmetry. The stalk, which consists of numerous disks held together by ligaments, supports a calyx or cup made of circlets of calcerous plates. In Comatulids, the stalk develops following the larval stage, but the juveniles shed all but the topmost disk to take up a free-living existence. Five often branched arms, which consist of articulated series of ossicles, extend from the oral plate and form the food-capture mechanism of Articulata. The arms of Articulata are pinnulate in that they have alternating pinnules branching out along them to effectively increase the surface area for feeding. These pinnules all have ciliated ambulacral grooves that converge to form larger grooves in the arms that lead down to the mouth located beside the anus on the upper surface of the oral plate. [2]

Articulata are passive suspension feeders. They capture algae with triplets of tube feet located on the pinnules, and the ciliated ambulacral canals transport this algae to the mouth. Although they are passive feeders, some Articulata have been observed to move to better feeding areas either with locomotory mechanisms at the base of the stalk or by detaching and pulling themselves with their arms. As of 2004, there are 540 described species of living Articulata that fall into two major orders. The bourgueticrinids which have the traditional stalked body form account for about 15% percent of the known species while the comatulids are unstalked and account for most of the rest. [2]

Classification

According to the World Register of Marine Species, Articulata includes the following families: [3]

Related Research Articles

<span class="mw-page-title-main">Crinoid</span> Class of echinoderms

Crinoids are marine animals that make up the class Crinoidea, one of the classes of the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. Those crinoids which, in their adult form, are attached to the sea bottom by a stalk are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, being members of the largest crinoid order, Comatulida. They live in both shallow water and in depths as great as 9,000 meters (30,000 ft).

<span class="mw-page-title-main">Comasteridae</span> Family of crinoids

Comasteridae is a family of crinoids.

<span class="mw-page-title-main">Bathycrinidae</span> Family of crinoids

Bathycrinidae is a family of echinoderms in the class Crinoidea. It contains the following genera and species:

<span class="mw-page-title-main">Antedonidae</span> Family of crinoids

Antedonidae is a family of crinoids or feather stars in the phylum Echinodermata. Members of the family are unstalked and have ten feathery arms. They can move about freely and have clawed cirri to attach them temporarily to structures.

<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.

<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>Davidaster rubiginosus</i> Species of crinoid

Davidaster rubiginosus or the orange sea lily is a species of crinoid in the family Comatulidae. At one time it was classified as Nemaster rubiginosa but the World Register of Marine Species has determined that the valid name is Davidaster rubiginosus. It is found on reefs in the tropical western Atlantic and the Caribbean Sea.

Davidaster discoideus or the beaded crinoid is a species of feather star in the family Comatulidae. It was previously known as Nemaster discoidea but the World Register of Marine Species has determined that the valid name is Davidaster discoideus. It is found on reefs in the Caribbean Sea and northern coast of South America.

<i>Comaster schlegelii</i> Species of crinoid

Comaster schlegelii, the variable bushy feather star, is a crinoid in the family Comatulidae. It was previously classified as Comanthina schlegeli but further research showed that it was better placed in the genus Comaster. It is found on shallow water reefs in the western Pacific Ocean.

<i>Oxycomanthus bennetti</i> Species of echinoderm

Oxycomanthus bennetti, the Bennett's feather star, is a species of crinoid belonging to the family Comatulidae. It is found in shallow water in the Indo-Pacific between northern Australia and southeast Asia.

<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>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.

<span class="mw-page-title-main">Isocrinidae</span> Family of crinoids

Isocrinidae is one of four extant families of crinoids in the order Isocrinida.

<span class="mw-page-title-main">Comatulidae</span> Family of crinoids

Comatulidae is a family of comatulid crinoids. Since 2015, it replaces the family Comasteridae.

<i>Florometra serratissima</i> Species of crinoid

Florometra serratissima is a species of crinoid or feather star in the family Antedonidae. It is found off the Pacific coast of North America, usually in deep water.

<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>Aporometra paedophora</i> Species of crinoid

Aporometra paedophora is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It was first found at a depth of 22 fathoms off the Manning River on the New South Wales coast. Other specimens were found off the coast of Bunbury, Western Australia at depths between 9 and 15 m. Based on morphological evidence of four specimens of A. paedophora, Helgen & Rouse believe that this may not be a separate species from Aporometra wilsoni.

<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.

References

  1. Wright, David F.; Ausich, William I.; Cole, Selina R.; Peter, Mark E.; Rhenberg, Elizabeth C. (2017-02-22). "Phylogenetic taxonomy and classification of the Crinoidea (Echinodermata)". Journal of Paleontology. 91 (4): 829–846. doi:10.1017/jpa.2016.142. ISSN   0022-3360.
  2. 1 2 Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. pp. 917–918. ISBN   81-315-0104-3.
  3. Messing, Charles (2007). "Articulata". WoRMS. World Register of Marine Species . Retrieved 31 March 2019.