name = Brachiopoda
image_width = 250px
image_caption = Living brachiopods
phylum = Brachiopoda
phylum_authority = Duméril, 1806
subdivision_ranks = Subphyla and classes
subdivision = See Classification
diversity_link = List of brachiopod genera
diversity = About 4,000 genera
Latin"brachium", arm + New Latin "-poda", foot) are a small phylum of benthic invertebrates. Also known as lamp shells (or lampshells), "brachs" or Brachiopoda, they are sessile, two-valved, marine animals with an external morphology superficially resembling pelecypods (for instance, clams) of phylum Molluscato which they are not closely related. It is estimated by paleobiologists that 99 percent of all documented lamp-shell species are both fossils and extinct. [ See, for instance, data provided by paleontologistW. H. Easton (1960) in "Invertebrate Paleontology" (New York: Harper and Brothers). ]
Despite superficial similarities, bivalves and brachiopods differ markedly:
Bivalves 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 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 muscles to hold their two valves closed, and they open them by means of an external or internal ligamentonce the adductor muscles are relaxed. Brachiopods use internal diductormuscles 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
substrateby means of a fleshy "stalk" or pedicle. In contrast, although some bivalves ( pelecypods such as oysters, mussels and the extinct rudists) are fixed to the substrate, "most" are free-moving, usually by means of a muscular "foot".
Furthermore, brachiopod shells may be made of either Calcium
Phosphateor -- much more commonly -- Calcium Carbonate(CaCO3), as mollusks generally are.  Lastly, in contrast to most bivalves, some extinct brachiopods exhibit elaborate flanges and spines.
July 16, 1986, the Kentucky State Legislature designated the brachiopod to be the Kentucky state fossil.
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
pedicleor resting on muddy bottoms. Brachiopods are suspension feeders with a distinctive feeding organ called a lophophore, which is found in two other animal phyla ( Bryozoaand 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 mm (¼ 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.
The earliest unequivocal brachiopods in the
fossil recordoccur 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 Neoproterozoicstrata, although their assignment remains uncertain. Brachiopods are extremely common fossils throughout the Paleozoic. The major shift came with the 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 Bryozoaand possibly the Entoprocta, these phyla constitute the informal superphylum Lophophorata.
The inarticulate brachiopod genus "Lingula" is the oldest, relatively
evolutionarily 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.
Ordovicianand Silurianperiods, 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 mussels) do today. In some places, large sections of limestonestrata 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
extinctions 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 fossils when correlating strata across large areas.
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
fossils. In the last 40 years further analysis of the fossil record and of living brachiopods, including 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", 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. Brachiopod Taxonomy
Extant taxa in green, extinct taxa in grey
after Williams, Carlson, and Brunton,
2000 Subphyla Classes Orders Extinct Linguliformea Lingulata Lingulida no Siphonotretida Ordovician Acrotretida Devonian Paterinata Paterinida Ordovician Craniformea Craniforma Craniida no Craniopsida Carboniferous Trimerellida Silurian Rhychonelliformea Chileata Chileida Cambrian Dictyonellidina Permian Obolellata Obolellida Cambrian Kutorginata Kutorginida Cambrian Strophomenata Orthotetidina Permian Triplesiidina Silurian Billingselloidea Ordovician Clitambonitidina Ordovician Strophomenida Carboniferous Productida Permian Rhynchonellata Protorthida Cambrian Orthida Carboniferous Pentamerida Devonian Rhynchonellida no Atrypida Devonian Spiriferida Jurassic Thecideida no Athyridida Cretaceous Terebratulida no
List of brachiopod genera
* [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]
*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
*  http://www.scienceforums.net/forum/showthread.php?p=339638
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Look at other dictionaries:
Brachiopod — Brach i*o*pod, n. [Cf.F. brachiopode.] (Zo[ o]l.) One of the Brachiopoda, or its shell. [1913 Webster] || … The Collaborative International Dictionary of English
brachiopod — (n.) bivalve mollusk, 1836, Modern Latin, from Gk. brakhion arm (see BRACHIO (Cf. brachio )) + pous foot (see FOOT (Cf. foot)). They have long spiral arms on either side of their mouths … Etymology dictionary
brachiopod — [brā′kē ō päd΄, brak′ēō päd΄] n. [< ModL < BRACHIO + POD] any of a phylum (Brachiopoda) of marine animals with hinged upper and lower shells enclosing two armlike parts with tentacles that are used for guiding minute food particles to the… … English World dictionary
brachiopod — noun Etymology: ultimately from Latin bracchium + Greek pod , pous foot more at foot Date: 1836 any of a phylum (Brachiopoda) of marine invertebrates with bivalve shells within which is a pair of arms bearing tentacles by which a current of water … New Collegiate Dictionary
brachiopod — /bray kee euh pod , brak ee /, n. 1. any mollusklike, marine animal of the phylum Brachiopoda, having a dorsal and ventral shell; a lamp shell. adj. 2. Also, brachiopodous /bray kee op euh deuhs, brak ee/. belonging or pertaining to the… … Universalium
brachiopod — noun /ˈbɹækɪəˌpɒd/ Any of many marine invertebrates, of the phylum Brachiopoda, that have bivalve dorsal and ventral shells with two tentacle bearing arms that capture food Syn: lampshell … Wiktionary
brachiopod — n. marine invertebrate animal that has hinged shells that close in on tentacles … English contemporary dictionary
brachiopod — [ brakɪə(ʊ)pɒd] noun Zoology a marine invertebrate of the phylum Brachiopoda, which comprises the lamp shells. Origin from mod. L. Brachiopoda, from Gk brakhiōn arm + pous, pod foot … English new terms dictionary
brachiopod — brach·i·o·pod … English syllables
brachiopod — bra•chi•o•pod [[t]ˈbreɪ ki əˌpɒd, ˈbræk i [/t]] n. ivt any superficially clamlike marine animal of the phylum Brachiopoda, having unequal dorsal and ventral shells enclosing a pair of ciliated food gathering appendages • Etymology: 1830–40; <… … From formal English to slang