# Rhynchonellida > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Rhynchonellida > Markdown URL: https://mediated.wiki/source/Rhynchonellida.md > Source: https://en.wikipedia.org/wiki/Rhynchonellida > Source revision: 1328188472 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{short description|Order of brachiopods}} {{Automatic taxobox | fossil_range = {{fossil range|Upper Ordovician|Recent}} | image = Rhynchotremadentatum.jpg | image_caption = ''Rhynchotrema dentatum'', a rhynchonellid brachiopod from the [Cincinnatian](/source/Cincinnatian_(geology)) (Upper [Ordovician](/source/Ordovician)) of SE [Indiana](/source/Indiana). | taxon = Rhynchonellida | authority = Kuhn, 1949 | subdivision_ranks = Subgroups | subdivision = See text. }} [[File:Hemithiris psittacea 132279100.jpg|thumb|''[Hemithiris psittacea](/source/Hemithiris_psittacea)'', a living rhynchonellide]] [[File:Ladogia Nalivkin, 1941 Devonian Western Russia.JPG|thumb|''Ladogia'' sp., a rhynchonellid brachiopod from the [Devonian](/source/Devonian) of western [Russia](/source/Russia) (side view).]] The [taxonomic](/source/Taxonomy_(biology)) [order](/source/order_(biology)) '''Rhynchonellida''' is one of the two main groups of living [articulate](/source/Articulata_(Brachiopoda)) [brachiopod](/source/brachiopod)s, the other being the order [Terebratulida](/source/Terebratulida). They are recognized by their strongly ribbed wedge-shaped or nut-like [shell](/source/brachiopod)s, and the very short [hinge](/source/hinge) line. The hinges come to a point, a superficial resemblance to many ([phylogenetic](/source/phylogenetic)ally unrelated) [bivalve](/source/bivalve) [mollusk](/source/mollusk) shells. The loss of the hinge line was an important evolutionary innovation, '''rhynchonellids''' being the first truly non-strophic shells with a purely internal articulation (teeth-sockets). Strong radiating ribs are common in this group; and there are generally very strong plications or accordion-like folds on the [sulcus](/source/Sulcus_(anatomy)) (the long middle section) of the shell. This probably helps regulate the flow of water in and out of the shell. All rhynchonellids are biconvex (have a bulbous shell), and have a fold located in the [brachial valve](/source/brachial_valve). This means that the [commissure](/source/commissure), the line between the two valves or shells, is zigzagged, a distinguishing characteristic of this group. The prominent beak of the [pedicle valve](/source/pedicle_valve) usually overlaps that of the brachial valve, in order to allow the shell to open and close. There is usually a functional [pedicle](/source/Brachiopod) although the [delthyrium](/source/delthyrium) may be partially closed. Morphologically, the rhynchonellid has changed little since its appearance during the [Ordovician](/source/Ordovician) period. It seems to have evolved from [pentamerid](/source/pentamerid)s, and in turn gave rise to the first [atrypid](/source/atrypid)s and [athyrid](/source/athyrid)s, both of which are characterized by the development of a complex spiral brachidium. Although much diminished by the [terminal Paleozoic extinction](/source/Permian_extinction), it experienced a revival during the Early Jurassic period, and became the most abundant of all brachiopods during the [Mesozoic](/source/Mesozoic) Era. ==Classification== This classification down to the level of [genera](/source/genera) is based on Kazlev{{cite web | author = M. Alan Kazlev | accessdate = March 10, 2006 | url = http://www.palaeos.com/Invertebrates/Lophotrochozoa/Brachiopoda/Rhynchonellida.htm | title = Order Rhynchonellida | url-status = dead | archiveurl = https://web.archive.org/web/20060313163526/http://www.palaeos.com/Invertebrates/Lophotrochozoa/Brachiopoda/Rhynchonellida.htm | archivedate = March 13, 2006 }} and Emig.{{cite web | author = Christian C. Emig | title = Systematics of extant brachiopod taxa | url = http://paleopolis.rediris.es/BrachNet/CLASS/DOC/Classext.pdf | accessdate = March 10, 2006 | url-status = dead | archiveurl = https://web.archive.org/web/20060513051227/http://paleopolis.rediris.es/BrachNet/CLASS/DOC/Classext.pdf | archivedate = May 13, 2006 }} '''Extant subgroups''' * Superfamily [Pugnacoidea](/source/Pugnacoidea) ** Family [Basiliolidae](/source/Basiliolidae) *** Subfamily [Acanthobasiliolinae](/source/Acanthobasiliolinae) **** ''[Acanthobasiliola](/source/Acanthobasiliola)'' *** Subfamily [Basiliolinae](/source/Basiliolinae) **** ''[Basiliola](/source/Basiliola)'' **** ''[Basiliolella](/source/Basiliolella)'' **** ''[Eohemithiris](/source/Eohemithiris)'' **** ''[Rhytirhynchia](/source/Rhytirhynchia)'' *** Subfamily uncertain **** ''[Striarina](/source/Striarina)'' * Superfamily [Dimerelloidea](/source/Dimerelloidea) ** Family [Cryptoporidae](/source/Cryptoporidae) **** ''[Aulites](/source/Aulites)'' **** ''[Cryptopora](/source/Cryptopora_(brachiopod))'' * Superfamily [Norelloidea](/source/Norelloidea) ** Family [Frieleiidae](/source/Frieleiidae) *** Subfamily [Freileiinae](/source/Freileiinae) **** ''[Frieleia](/source/Frieleia)'' **** ''[Compsothyris](/source/Compsothyris)'' **** ''[Grammetaria](/source/Grammetaria)'' **** ''[Sphenarina](/source/Sphenarina)'' *** Subfamily [Hispanirhynchiinae](/source/Hispanirhynchiinae) **** ''[Abyssorhynchia](/source/Abyssorhynchia)'' **** ''[Hispanirhynchia](/source/Hispanirhynchia)'' **** ''[Manithyris](/source/Manithyris)'' **** ''[Parasphenarina](/source/Parasphenarina)'' *** Subfamily [Neorhynchiinae](/source/Neorhynchiinae) **** ''[Neorhynchia](/source/Neorhynchia)'' ** Family [Tethyrhynchiidae](/source/Tethyrhynchiidae) **** ''[Tethyrhynchia](/source/Tethyrhynchia)'' * Superfamily [Hemithiridoidea](/source/Hemithiridoidea) ** Family [Hemithyrididae](/source/Hemithirididae) **** ''[Hemithiris](/source/Hemithiris)'' **** ''[Pemphixina](/source/Pemphixina)'' ** Family [Notosariidae](/source/Notosariidae) **** ''[Notosaria](/source/Notosaria)'' '''Extinct subgroups''' * Superfamily [Ancistrorhynchoidea](/source/Ancistrorhynchoidea) * Superfamily [Camarotoechioidea](/source/Camarotoechioidea) * Superfamily [Lambdarinoidea](/source/Lambdarinoidea) * Superfamily [Rhynchonelloidea](/source/Rhynchonelloidea) * Superfamily [Rhynchoporoidea](/source/Rhynchoporoidea) * Superfamily [Rhynchotetradoidea](/source/Rhynchotetradoidea) * Superfamily [Rhynchotrematoidea](/source/Rhynchotrematoidea) * Superfamily [Stenoscismatoidea](/source/Stenoscismatoidea) * Superfamily [Uncinuloidea](/source/Uncinuloidea) * Superfamily [Wellerelloidea](/source/Wellerelloidea) ==References== {{Reflist}} ==External links== * [https://web.archive.org/web/20060207000415/http://www.geo.arizona.edu/geo3xx/geo308_fall2002/4brachiopds.htm Phylum Brachiopoda] {{Taxonbar|from=Q2885825}} {{Brachiopod orders}} Category:Rhynchonellida Category:Brachiopod orders Category:Extant Ordovician first appearances --- Adapted from the Wikipedia article [Rhynchonellida](https://en.wikipedia.org/wiki/Rhynchonellida) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rhynchonellida?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.