Brachiopod
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Slambo
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Reverted 1 edit by [[Special:Contributions/90.193.112.26|90.193.112.26]] identified as [[WP:VAND|vandalism]] to last revision by [[User:JacobDyer08|JacobDyer08]]. ([[WP:TW|TW]])
{{AnimalsCleanup}}
{{refimprove|date=January 2007}}
{{Taxobox
| name = Brachiopoda
| fossil_range = [[Cambrian]] - Recent
| image = Usgs_boulder_brachiopods.jpg
| image_width = 250px
| image_caption = Living brachiopods
| regnum = [[Animal]]ia
| phylum = '''Brachiopoda'''
| phylum_authority = [[André Marie Constant Duméril|Duméril]], 1806
| subdivision_ranks = [[Subphylum|Subphyla]] and [[class (biology)|class]]es
| subdivision = See [[Brachiopod#Classification|Classification]]
| diversity_link = List of brachiopod genera
| diversity = About 4,000 [[genus|genera]]
}}
'''Brachiopods''' (from [[Latin]] ''bracchium'', arm + New Latin ''-poda'', foot) are a small [[Phylum (biology)|phylum]] of [[benthic]] [[invertebrate]]s. Also known as '''lamp shells''' (or '''lampshells'''), "'''brachs'''" or '''Brachiopoda''', they are [[sessile]], two-valved, [[Marine (ocean)|marine]] [[animal]]s with an external [[morphology (biology)|morphology]] superficially resembling [[Bivalvia|pelecypod]]s (for instance, [[clam]]s) of phylum [[Mollusca]] to which they are not closely related. It is estimated by [[paleobiology|paleobiologist]]s that 99 percent of all documented lamp-shell species are both [[fossil]]s and [[extinct]].<ref> See, for instance, data provided by [[paleontologist]] W. H. Easton (1960) in ''[[Invertebrate paleontology|Invertebrate Paleontology]]'' (New York: Harper and Brothers). </ref>
<!-- Some of this probably should be moved further down into the below sections -->
Despite superficial similarities, bivalves and brachiopods differ markedly: [[Bivalve]]s usually have a plane of symmetry between the valves of the shell, which are mirror images of each other; most brachiopods have a plane of [[symmetry (biology)#Bilateral symmetry|bilateral symmetry]] ''through'' the valves and perpendicular to the [[hinge]]. The two brachiopod valves differ in shape and size from one another. Bivalves use [[adductor muscle]]s to hold their two valves closed, and they open them by means of an external or internal [[ligament]] once the adductor muscles are relaxed. Brachiopods use internal [[diductor]] muscles to pull their two valves apart; they close the two with adductor muscles.
A second major difference is that most brachiopods are attached to the [[substrate]] by means of a fleshy "stalk" or [[pedicle]]. In contrast, although some bivalves ([[pelecypod]]s such as [[oyster]]s, [[mussel]]s and the extinct [[rudist]]s) are fixed to the substrate, ''most'' are free-moving, usually by means of a muscular "foot".
Furthermore, brachiopod shells may be either [[Phosphorus|phosphatic]] or -- much more commonly -- [[Calcite|calcitic]], as mollusks generally are. Only rarely do brachiopods produce [[aragonite|aragonitic]] shells, which are composed of a less-permanent form of [[calcium carbonate]]. Lastly, in contrast to most bivalves, some extinct brachiopods exhibit elaborate [[flange]]s and [[spine]]s.
On [[July 16]], [[1986]], the Kentucky State Legislature designated the brachiopod to be the [[Kentucky]] [[state fossil]].
==General description==
[[Image:Lingula anatina 2.jpg|thumb|right|''[[Lingula anatina]]'']]
Brachiopods may be divided into two types: ''inarticulate brachiopods'' are held together entirely by musculature, whereas ''articulate brachiopods'' have a hinge-like articulation between the shells. All brachiopods are marine and are found either attached to substrates by a structure called a [[pedicle]] or resting on muddy bottoms. Brachiopods are suspension feeders with a distinctive feeding organ called a [[lophophore]], which is found in two other animal phyla ([[Bryozoa]] and [[Phoronida]]). Modern brachiopods generally live in areas of cold water, either near the poles or in deep parts of the ocean.
Modern brachiopods range in shell size from less than 5 [[millimetre|mm]] (¼ [[inch|in]]) to just over 8 cm (3 in). Fossil brachiopods generally fall within this size range, but some adult species have a shell of less than 1 mm across, and a few gigantic forms have been found measuring up to 38½ cm (15 in) in width.
==Evolutionary history==
[[Image:Onniella.jpg|thumb|left|Brachiopod fossils are often found in dense assemblages, such as these specimens of the [[Ordovician]] species ''Onniella meeki''.]]
[[Image:Brachiopoda-morphology.png|thumb|300px|right|Brachiopod morphology]]
[[Image:Brachiopod Neospirifer.jpg|thumb|A [[Carboniferous]] brachiopod ''Neospirifer condor'', from Bolivia. The specimen is 7 cm across.]]
[[Image:EncrustedStroph.JPG|thumb|An [[Ordovician]] [[strophomenid]] brachiopod with encrusting inarticulate brachiopods (the craniid ''Philhedra'')and a [[bryozoan]].]]
[[Image:HederellaOH3.jpg|thumb|left|A [[Devonian]] spiriferid brachiopod from Ohio which served as a host substrate for a colony of [[hederellid]]s. The specimen is 5 cm wide.]]
[[Image:Syringothyris01.JPG|thumb|left|''Syringothyris'' sp.; a spiriferid brachiopod from the Logan Formation (Lower [[Carboniferous]]) of [[Wooster, Ohio]] (internal molds).]]
The earliest unequivocal brachiopods in the [[fossil record]] occur in the early [[Cambrian]], with the hingeless, inarticulate forms appearing first, followed soon thereafter by the hinged, articulate forms. Possible brachiopods have also been found in much older upper [[Neoproterozoic]] strata, although their assignment remains uncertain. Brachiopods are extremely common fossils throughout the [[Paleozoic]]. The major shift came with the [[Permian-Triassic extinction event|Permian extinction]]. Before this [[extinction event]], brachiopods were more numerous and diverse than bivalve mollusks. Afterwards, in the [[Mesozoic]], their diversity and numbers were drastically reduced, and they were largely replaced by bivalve mollusks. Mollusks continue to dominate today, and the remaining orders of brachiopods survive largely in fringe environments of more extreme cold and depth.
The most abundant modern brachiopods are the Class [[Terebratulida]]. The perceived resemblance of terebratulid shells to ancient oil lamps gave the brachiopods their common name "lamp shell". The phylum most closely related to Brachiopoda is probably the small phylum [[Phoronida]] (known as "horseshoe worms"). Along with the [[Bryozoa]] and possibly the [[Entoprocta]], these phyla constitute the informal superphylum [[lophophorate|Lophophorata]].
The inarticulate brachiopod genus ''Lingula'' is the oldest, relatively [[evolution]]arily unchanged animal known. The oldest ''Lingula'' fossils are found in Lower Cambrian rocks dating to roughly 550 million years ago. The origin of brachiopods is unknown. A possible ancestor is a sort of ancient "armored slug" known as ''[[Halkieria]]'' that was recently been found to have had small brachiopod-like shields on its head and tail.
During the [[Ordovician]] and [[Silurian]] periods, brachiopods became adapted to life in most marine environments and became particularly numerous in shallow water habitats, in some cases forming whole banks in much the same way as bivalves (such as [[mussel]]s) do today. In some places, large sections of [[limestone]] [[Stratum|strata]] and reef deposits are composed largely of their shells.
Throughout their long geological history, the brachiopods have gone through several major proliferations and diversifications, and have also suffered from major [[extinction]]s as well.
It has been suggested that the slow decline of the brachiopods over the last 100 million years or so is a direct result of (1) the rise in diversity of filter feeding bivalves, which have ousted the brachiopods from their former habitats; (2) the increasing disturbance of sediments by roving deposit feeders (including many burrowing bivalves); and/or (3) the increased intensity and variety of shell-crushing predation. However, it should be noted that the greatest successes for the bivalves have been in habitats which have never been adopted by the brachiopods, such as burrowing.
The abundance, diversity, and rapid evolution of brachiopods during the Paleozoic make them useful as [[index fossil]]s when correlating strata across large areas.
==Classification==<!-- This section is linked from [[Brachiopod]] -->
In older classification schemes, Phylum Brachiopoda was divided into two classes: Articulata and Inarticulata. Since most orders of brachiopods have been extinct since the end of the Paleozoic Era, classifications have always relied extensively on the morphology (that is, the shape) of [[fossil]]s. In the last 40 years further analysis of the fossil record and of living brachiopods, including [[genetics|genetic]] study, has led to changes in [[taxonomy]].
The taxonomy is still unstable, however, so different authors have made different groupings. In their 2000 article as part of the ''Treatise on [[Invertebrate paleontology|Invertebrate Paleontology]]'', Alwyn Williams, Sandra J. Carlson, and C. Howard C. Brunton present current ideas on brachiopod classification; their grouping is followed here. They subdivide Brachiopoda into three subphyla, eight classes, and 26 orders. These categories are believed to be approximately [[phylogenetic]]. Brachiopod diversity declined significantly at the end of the Paleozoic. Only five orders in three classes include forms which survive today, a total of between 300 and 500 extant species. Compare this to the mid-Silurian Period, when 16 orders of brachiopods coexisted.
<table border=1 cellspacing=0 align="center" style = "margin-left: 0.5em;">
<tr><td style="background:#eeeeee" colspan=4 align="center">'''Brachiopod Taxonomy''' <br>
Extant taxa in green, extinct taxa in grey<br>
<small>after Williams, Carlson, and Brunton, [[2000]]</small>
<tr><th>[[Subphylum|Subphyla]]<th>[[Class (biology)|Class]]es<th>[[Order (biology)|Order]]s<th>Extinct
<tr><td rowspan=4 style="background: #00DD00">[[Linguliformea]]<td rowspan=3 style="background: #00DD00">[[Lingulata]]
<td style="background: #00DD00">[[Lingulida]]<td style="background: #00DD00">no
<tr style="background:#dedede"><td>[[Siphonotretida]]<td>[[Ordovician]]
<tr style="background:#dedede"><td>[[Acrotretida]]<td>[[Devonian]]
<tr style="background:#dedede"><td>[[Paterinata]]<td>[[Paterinida]]<td>Ordovician
<tr><td rowspan=3 style="background: #00DD00">[[Craniformea]]<td rowspan=3 style="background: #00DD00">[[Craniforma]]
<td style="background: #00DD00">[[Craniida]]<td style="background: #00DD00">no
<tr style="background:#dedede"><td>[[Craniopsida]]<td>[[Carboniferous]]
<tr style="background:#dedede"><td>[[Trimerellida]]<td>[[Silurian]]
<tr><td rowspan=19 style="background: #00DD00">[[Rhychonelliformea]]
<td rowspan=2 style="background:#dedede">[[Chileata]]
<td style="background:#dedede">[[Chileida]]<td style="background:#dedede">[[Cambrian]]
<tr style="background:#dedede"><td>[[Dictyonellidina]]<td>[[Permian]]
<tr style="background:#dedede"><td>[[Obolellata]]<td>[[Obolellida]]<td>Cambrian
<tr style="background:#dedede"><td>[[Kutorginata]]<td>[[Kutorginida]]<td>Cambrian
<tr style="background:#dedede"><td rowspan=6>[[Strophomenata]]
<td>[[Orthotetidina]]<td>Permian
<tr style="background:#dedede"><td>[[Triplesiidina]]<td>Silurian
<tr style="background:#dedede"><td>[[Billingselloidea]]<td>Ordovician
<tr style="background:#dedede"><td>[[Clitambonitidina]]<td>Ordovician
<tr style="background:#dedede"><td>[[Strophomenida]]<td>Carboniferous
<tr style="background:#dedede"><td>[[Productida]]<td>Permian
<tr><td rowspan=9 style="background: #00DD00">[[Rhynchonellata]]
<td style="background:#dedede">[[Protorthida]]<td style="background:#dedede">Cambrian
<tr style="background:#dedede"><td>[[Orthida]]<td>Carboniferous
<tr style="background:#dedede"><td>[[Pentamerida]]<td>Devonian
<tr style="background: #00DD00"><td>[[Rhynchonellida]]<td>no
<tr style="background:#dedede"><td>[[Atrypida]]<td>Devonian
<tr style="background:#dedede"><td>[[Spiriferida]]<td>[[Jurassic]]
<tr style="background: #00DD00"><td>[[Thecideida]]<td>no
<tr style="background:#dedede"><td>[[Athyridida]]<td>[[Cretaceous]]
<tr style="background: #00DD00"><td>[[Terebratulida]]<td>no
</table>
==See also==
*[[List of brachiopod genera]]
==Footnotes==
<references/>
==External links==
{{commonscat|Brachiopoda}}
*[http://www.ucmp.berkeley.edu/brachiopoda/brachiopoda.html UC-Berkeley Museum of Paleontology]
* [http://www.palaeos.com/Invertebrates/Lophotrochozoa/Brachiopoda/E0A0E0Brachiopoda.htm Palaeos Brachiopoda]
*[http://paleopolis.rediris.es/BrachNet/ BrachNet]
*[http://www.kgs.ku.edu/Extension/fossils/brachiopod.html Information from the Kansas Geological Survey]
*[http://perso.wanadoo.fr/jean-ours.filippi/brach/anglais/poursavoirplusang22.html site of R.Filippi]
*[http://paleopolis.rediris.es/Brachiopoda_Phoronida_databases/ Brachiopoda World Database]
==References==
*{{cite book|last=Williams|first=A|coauthors=Carlson, S.J., and Brunton, C.H.C.|year=2000|chapter=Brachiopod classification|volume=2|editor=Williams, A. et al. |title=Brachiopoda (revised)|}} Part H of {{cite book|title=Treatise on Invertebrate Paleontology|editor=Kaesler, R.L.| location=Boulder, Colorado and Lawrence, Kansas|publisher=Geological Society of America and The University of Kansas |id=ISBN 0-8137-3108-9}}
[[Category:Brachiopods| ]]
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