Articulata are a subclass or superorder within the class
Crinoidea
Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...
, 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
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
period although other, now extinct crinoid groups, originated in the
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
.
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
The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...
, 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.
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.
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Classification
According to the World Register of Marine Species
The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms.
Content
The content of the registry is edited and maintained by scientific specialist ...
, Articulata includes the following families:
* order Comatulida
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 ...
Clark, 1908
** super-family Antedonoidea Norman, 1865
*** family Antedonidae
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. Norman, 1865
*** family Pentametrocrinidae
Pentametrocrinidae is a family of echinoderms belonging to the order Comatulida
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 f ...
AH Clark, 1908
*** family Zenometridae AH Clark, 1909
** super-family Atelecrinoidea Bather, 1899
*** family Atelecrinidae
Atelecrinidae is a Family (biology), family of crinoids or feather stars in the phylum Echinodermata. It was first described by Francis Arthur Bather in 1899.
Genera
The following genera are in the family Atelecrinidae:
* ''Adelatelecrinus'' Mes ...
Bather, 1899
** super-family Comatuloidea
Comatulidae is a family of comatulid crinoids. Since 2015, it replaces the family Comasteridae.
Description and characteristics
This family is of recent restoration, and still has no consensual description. However the description of the fam ...
Fleming, 1828
*** family Comatulidae
Comatulidae is a family of comatulid crinoids. Since 2015, it replaces the family Comasteridae.
Description and characteristics
This family is of recent restoration, and still has no consensual description. However the description of the fam ...
Fleming, 1828
** super-family Himerometroidea AH Clark, 1908
*** family Colobometridae
''Colobometridae'' is a family of crinoids belonging to the order Comatulida
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 fac ...
AH Clark, 1909
*** family Eudiocrinidae
Eudiocrinidae is a family of echinoderms belonging to the order Comatulida
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 ...
AH Clark, 1907
*** family Himerometridae
Himerometridae is a family of echinoderms belonging to the order Comatulida
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 facin ...
AH Clark, 1907
*** family Mariametridae
Mariametridae is a family of echinoderms belonging to the order Comatulida
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 ...
AH Clark, 1909
*** family Zygometridae
''Zygometridae'' is a family of echinoderms belonging to the order Comatulida
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 fac ...
AH Clark, 1908
** super-family Notocrinoidea Mortensen, 1918
*** family Aporometridae
Aporometridae is a monotypic family of crinoids, the only genus being ''Aporometra'', which contains three species, all endemic to the seas around Australia.
Description
Members of this family have five arms which subdivide near the base givin ...
HL Clark, 1938
*** family Notocrinidae Mortensen, 1918
** super-family † Paracomatuloidea Hess, 1951
** super-family Tropiometroidea AH Clark, 1908
*** family Asterometridae Gislén, 1924
*** family Calometridae AH Clark, 1911
*** family Charitometridae AH Clark, 1909
*** family Ptilometridae AH Clark, 1914
*** family Thalassometridae AH Clark, 1908
*** family Tropiometridae AH Clark, 1908
** Comatulida ''incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
''
*** family Atopocrinidae Messing, 2011 (in Hess & Messing, 2011)
*** family Bathycrinidae
Bathycrinidae is a family of echinoderms in the class Crinoidea
Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while th ...
Bather, 1899
*** family Bourgueticrinidae
Bourgueticrinidae is a family of crinoids, containing 2 genera.
Genera
* ''Conocrinus
''Conocrinus'' is a genus of sea lilies in the family Bourguticrinidae, containing 6 species.
Species
* '' Conocrinus cabiochi'' Roux, 1976
* '' Conocr ...
Loriol, 1882
*** family Guillecrinidae Mironov & Sorokina, 1998
*** family Phrynocrinidae AH Clark, 1907
*** family Septocrinidae Mironov, 2000
* order Cyrtocrinida
Cyrtocrinida is an order of sea lilies which contains two suborders and three families.
Characteristics
Members of this order have stems consisting of a single skeletal unit or a very small number of units. There are no cirri, and the expanded ...
** Sub-order Cyrtocrinina
*** family Sclerocrinidae
''Sclerocrinidae'' is a family of echinoderms belonging to the order Millericrinida.
Genera:
* '' Ascidicrinus'' Hess, Salamon & Gorzelak, 2011
* '' Cyrtocrinus'' Jaekel, 1892
* '' Hemicrinus'' d'Orbigny, 1850
* '' Neogymnocrinus'' Hess, 200 ...
Jaekel, 1918
** Sub-order Holopodina
*** family Eudesicrinidae
''Eudesicrinidae'' is a family of echinoderms belonging to the order Millericrinida.
Genera:
* ''Eudesicrinus'' Loriol, 1882
* ''Proeudesicrinus'' Améziane-Cominardi & Bourseau, 1990
References
Cyrtocrinida
Echinoderm families
{{crino ...
Bather, 1899
*** family Holopodidae
Holopodidae is a family of echinoderms belonging to the order Cyrtocrinida
Cyrtocrinida is an order of sea lilies which contains two suborders and three families.
Characteristics
Members of this order have stems consisting of a single skeleta ...
Zittel, 1879
* order † Encrinida
** family † Encrinidae
* order Hyocrinida
Hyocrinida is an order of sea lilies which contains a single extant family, Hyocrinidae
''Hyocrinidae'' is a family of echinoderms belonging to the order Hyocrinida.
Genera:
* ''Ailsacrinus'' Mironov & Sorokina, 1998
* ''Anachalypsicrinus'' A ...
** family Hyocrinidae
''Hyocrinidae'' is a family of echinoderms belonging to the order Hyocrinida
Hyocrinida is an order of sea lilies which contains a single extant family, Hyocrinidae
''Hyocrinidae'' is a family of echinoderms belonging to the order Hyocrinid ...
Carpenter, 1884
* order Isocrinida
Isocrinida is an order of sea lilies which contains four extant families.
Characteristics
Members of this order are characterised by having a "heteromorphic" stalk; the stalk consists of a series of nodes with cirri, interspersed by several node ...
** Sub-order Isocrinina
*** family Cainocrinidae
''Cainocrinidae'' is a family of echinoderms belonging to the order Isocrinida
Isocrinida is an order of sea lilies which contains four extant families.
Characteristics
Members of this order are characterised by having a "heteromorphic" stalk; ...
Simms, 1988
*** family Isocrinidae
Isocrinidae is one of four extant families of crinoids in the order Isocrinida.Messing, C. (2014)Isocrinidae Gislén, 1924 In: Messing, C. (2014) World List of Crinoidea. Accessed through: World Register of Marine Species
Genera
*'' Hypalocrinu ...
Gislén, 1924
*** family Isselicrinidae
Isselicrinidae is one of four extant families of crinoids in the order Isocrinida.
Subfamilies and genera
* subfamily Diplocrininae Roux, 1981
** genus '' Cenocrinus'' Thomson, 1864 -- 1 species
** genus '' Endoxocrinus'' AH Clark, 1908 -- 5 s ...
Klikushkin, 1977
*** family Proisocrinidae
''Proisocrinus ruberrimus'' is a species of crinoids that is in the monotypic genus ''Proisocrinus''. The genus is in the monotypic family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) ...
Rasmussen, 1978
** Sub-order † Pentacrinitina
*** family † Pentacrinitidae Gray, 1842
* order †Millericrinida
Millericrinida is an order of articulate crinoids that originated in the Anisian
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until millio ...
References
{{Taxonbar, from=Q607044
Deuterostome subclasses
Triassic first appearances