Thecostraca is a

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

of marine

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s containing over 2,200 described species. Many species have

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

ic larvae which become sessile or

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

as adults. The most important subgroup are the

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...

s (subclass Cirripedia), constituting a little over 2,100 known species. The subgroup

Facetotecta Facetotecta is a poorly known subclass of thecostracan crustaceans. The adult forms have never been recognised, and the group is known only from its larvae, the "y- nauplius" and "y- cyprid" larvae. They are mostly found in the north Atlantic Oc ...

contains a single genus, ''Hansenocaris'', known only from the tiny planktonic nauplii called "y-larvae". These larvae have no known adult form, though it is suspected that they are parasites, and their affinity is uncertain. Some researchers believe that they may be larval

tantulocarida Tantulocarida is a highly specialised group of parasitic crustaceans that consists of about 33 species, treated as a class in superclass Multicrustacea. They are typically ectoparasites that infest copepods, isopods, tanaids, amphipods and os ...

ns. No larval tantulocaridans are currently known. The group

Ascothoracida Ascothoracida is a small group of crustaceans, comprising around 100 species. They are found throughout the world, and are parasites on cnidarians and echinoderms. Ascothoracida was previously ranked as an order within the infraclass Cirripedia ...

contains about 110 species, all parasites of

coelenterate Radiata or Radiates is a historical taxonomic rank that was used to classify animals with radially symmetric body plans. The term Radiata is no longer accepted, as it united several different groupings of animals that do not form a monophylet ...

s and

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

Classification

This article follows Chan et al. (2021) and the World Register of Marine Species in placing Thecostraca as a class of

Crustacea Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group c ...

and in the following classification of thecostracans down to the level of orders. Previously, Thecostraca was considered a subclass of Maxillopoda. Significant changes in the organization of Cirripedia's orders, families, and genera were introduced in 2021 by Chan et al. and accepted by the World Register of Marine Species. Class Thecostraca Gruvel, 1905 * Subclass

Lacaze-Duthiers, 1880 ** Order

Laurida Laurida is an order of crustacean in the infraclass Ascothoracida. It consists of the following families and genera: * Lauridae ** ''Baccalaureus'' ** '' Laura'' ** '' Polymarsypus'' ** '' Zoanthoecus'' * Petrarcidae ** '' Introcornia'' * ...

Grygier, 1987 ** Order

Dendrogastrida Dendrogastrida is an order of crustaceans belonging to the class Maxillopoda. Families: * Ascothoracidae Ascothoracidae is a family of crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals ...

Grygier, 1987 * Subclass

Grygier, 1985 * Subclass

Cirripedia A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...

Burmeister, 1834 ** Infraclass

Acrothoracica The Acrothoracica are an infraclass of barnacles. Acrothoracicans bore into calcareous material such as mollusc shells, coral, crinoids or hardgrounds, producing a slit-like hole in the surface known by the trace fossil name ''Rogerella''. A ...

Gruvel, 1905 *** Order

Lithoglyptida Lithoglyptida is an order of barnacles in the class Thecostraca Thecostraca is a class of marine invertebrates containing over 2,200 described species. Many species have planktonic larvae which become sessile or parasitic as adults. The most ...

Kolbasov, Newman & Hoeg, 2009 *** Order

Cryptophialida Cryptophialidae is a family of Acrothoracica The Acrothoracica are an infraclass of barnacles. Acrothoracicans bore into calcareous material such as mollusc shells, coral, crinoids or hardgrounds, producing a slit-like hole in the surface ...

Kolbasov, Newman & Hoeg, 2009 ** Infraclass

Rhizocephala Rhizocephala are derived barnacles that parasitise mostly decapod crustaceans, but can also infest Peracarida, mantis shrimps and thoracican barnacles, and are found from the deep ocean to freshwater. Together with their sister groups Thoracic ...

Müller, 1862 ** Infraclass Thoracica Darwin, 1854 *** Superorder Phosphatothoracica Gale, 2019 (

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

) **** Order Eolepadomorpha Chan et al., 2021 **** Order Iblomorpha Buckeridge & Newman, 2006 *** Superorder Thoracicalcarea Gale, 2015 **** Order Calanticomorpha Chan et al., 2021 **** Order Brachylepadomorpha Withers, 1923 **** Order Archaeolepadomorpha Chan et al., 2021 **** Order Verrucomorpha Pilsbry, 1916 **** Order Scalpellomorpha Buckeridge & Newman, 2006 **** Order Pollicipedomorpha Chan et al., 2021 **** Order

Balanomorpha The Balanomorpha are an order of barnacles, containing familiar acorn barnacles of the seashore. The order contains these families: * Austrobalanidae Newman & Ross, 1976 * Balanidae Leach, 1817 (acorn barnacles) * Bathylasmatidae Newman & Ro ...

Pilsbry, 1916

Phylogeny

The following cladogram depicts the internal relationships of the Thecostraca as of 2021.

References

External links

* {{Taxonbar, from=Q150628 Arthropod classes