Brachiopod
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| Brachiopoda Fossil range: Lower Cambrian–Recent |
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| Platystrophia ponderosa (Ordovician). Scale bar is 5.0 mm. | |
| Scientific classification | |
| Domain: | Eukarya |
| Kingdom: | Animalia |
| Phylum: | Brachiopoda Duméril, 1806 |
| Subphyla and classes | |
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See Classification |
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| Diversity | |
| About 4,000 genera | |
Brachiopods (from 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 bivalves to which they are not closely related. Approximately 99 percent of all brachiopod species are documented solely from the fossil record.[1]
Contents |
[edit] Description
(poss overview here)
[edit] Name
The scientific name "brachiopod" is formed from the Ancient Greek words βραχίων ("arm") and πούς ("foot").[2] They are often known as "lamp shells", since the curved shells of the class Rhynchonellida look rather like pottery oil-lamps.[3]
[edit] Distinguishing features
(to be completed)
[edit] Shells and their mechanisms
A brachiopod has two valves (shell sections) which are biomineralized. The brachial valve bears on its inner surface the the brachia ("arms") from which the phylum gets its name, and which supports the lophophore, used for filtering and respiration. The other is known as the pedicle valve, as its inner surface bears the stalk-like pedicle by which most brachiopods attach themselves to surface.[4] The brachial and pedicle valves are often call the dorsal ("upper") and ventral ("lower"),[4] but some paleontologists regard "dorsal" and "ventral" as incorrect terms, since they believe that the "ventral" valve was formed by folding of the upper surface under the body.[3] Irrespective of this debate, the valves of brachiopods are differently arranged of those of bivalve molluscs, which lie on the left and right sides of the body. In most brachiopod species both valves are convex, the surfaces often bear growth lines or other ornaments, and the pedicle valve is larger than the brachial. However, the linguids, which burrow into the seabed, have valves that are smoother, flatter and of similar size and shape.[4]
Brachiopod valves have a hinge, in which the rearmost end of the brachial valve rocks on an internal projection of the pedicle valve. The major classification of brachiopods is determined by the form of the hinges. The internal projections of articulate ("jointed") brachiopods have teeth which fit into sockets on the brachial valve, an arrangement that locks the valves together. Inarticulate brachiopods have no matching teeth and sockets, and their valves are held together only by muscles.[4]
All brachiopods have adductor muscles, that are set on the inside of the pedicle valve and close the valves by pulling on the part of the brachial valve ahead of the hinge. These muscles have both "quick" fibers that close the valves in emergencies and "catch" fibers that are slower but can keep the valves closed for long periods. Articulate brachiopods open the valves by means of abductor muscles, also known as diductors, which lay further to the rear and pull on the part of the brachial valve behind the hinge. Inarticulate brachiopods use a different opening mechanism, in which muscles reduce the length of the coelom (main body cavity) and make it bulge outwards, pushing the valves apart. Both classes open the valves to about 10°. The more complex set of muscles employed by inarticulate brachiopods can also operate the valves as scissors, a mechanism that linguids use to burrow.[4]
Each valve consists of three layers, a outer periostracum made of organic compounds and two biomineralized layers. Articulated brachiopods have a periostracum made of proteins, a "primary layer" of calcite (a form of calcium carbonate under that, and finally a mixture of proteins and calcite.[4] Inarticulate's shells have a similar sequence of layers, but their composition is different from that articulated brachiopods and also varies between the classes of inarticulate brachiopods. Linguids and discinids, which have pedicles, have a matrix of glycosaminoglycans (long, unbranched polysaccharides), in which other material are embedded: chitin in the periostracum;[4] apatite containing calcium phosphate in the primary biomineralized layer;[5] and a complex mixture in the innermost layer, containing collagen and other proteins, chitinophosphate and apatite.[4][6] Craniids, which have no pedicle and cement themselves directly hard surfaces, have a periostracum of chitin and mineralized layers of calcite.[4][7]
[edit] Mantle
Like molluscs, brachiopods have a mantle, an epithelium that lines the shell and encloses the internal organs. The brachiopod body occupies only about one-third of the internal space inside the shell, nearest the hinge. The rest of the space is lined with the mantle lobes, extensions that enclose a water-filled space in which sits the lophophore.[4] The coelom (main body cavity) extends into each lobe as a network of canals, which carry nutrients to the edges of the mantle.[8]
Relatively new cells in a groove on the edges of the mantle secrete material that extends the periostracum. These cells are gradually displaced to the upper side of the mantle by more recent cells in the groove, and switch to secreting the mineralized material of the shell valves. In other words, on the edge of the valve the periostracum is extended first, and then reinforced by extension of the mineralized layers under the periostracum.[8] In most species the edge of the mantle also bears movable bristles, often called chaetae or setae, that may help defend the animals and may act as sensors. In some brachiopods groups of chaetae help to channel the flow of water into and out of the mantle cavity.[4]
In most brachiopods, diverticula (hollow extensions) of the mantle penetrate through the mineralized layers of the valves into the periostraca. The function of these diverticula is uncertain and it is suggested that they may be storage chambers for chemicals such as glycogen, may secrete repellents to deter organisms that stick to the shell or may help in respiration.[4] Experiments show that a brachiopod's oxygen consumption drops if petroleum jelly is smeared on the shell, clogging the diverticula.[8] The body excluding lophophore and mantle cavity account for about 25% of the internal space among articulate species with diverticula, which are majority, but about 60% among articulate species that have no diverticula accounts. This suggests that the lophophore is a severe constraint on the body mass of brachiopods, and that diverticula provide extra living space.[9]
[edit] Lophophore
Like bryozoans and phoronids, brachiopods have a lophophore, a crown of tentacles whose cilia (fine hairs) create a water current that enables them to filter food particles out of the water. However a bryozoan or phoronid lophophore is a ring of tentacles mounted on a single, retracted stalk,[10][11] while the basic form of the brachiopod lophophore is U-shaped, forming the brachia ("arms") from which the phylum gets its name.[4] Brachiopod lophophores are non-retractable and occupy the frontmost two-thirds of the internal space, where the valves gape when opened. To provide enough filtering capacity in this restricted space, lophophores of larger brachiopods are folded in moderately to very complex shapes – loops and coils are common, and some species' lophophores resemble a hand with the fingers splayed.[4] In all species the lophophore is supported by cartilage and by a hydrostatic skeleton (in other words by the pressure of its internal fluid),[8] and the fluid extends into the tentacles.[4] Some articulate brachiopods also have a pair of brachidia, calcareous struts suspended on the inside of the brachial valve and shaped similarly to the lophophore that it supports.[8]
The tentacles bear cilia (fine mobile hairs) on their edges and along the center. The beating of the outer cilia drives a water current from the tips of the tentacles to their bases, where it exits. Food particles that collide with the tentacles are trapped by mucus, and the cillia down the middle drive this mixture to their bases.[12] A brachial groove runs rounds the bases of the tentacles, and its own cilia pass food along the groove towards the mouth.[4] The method used by brachiopod is known as "upstream collecting", as food particles are captured as they enter the field of cilia that creates the feeding current. This method is used by the related phoronids and bryozoans, and also by pterobranchs. Entoprocts use a similar-looking crown of tentacles, but theirs are solid and the flow runs from bases to tips, forming a "downstream collecting" system that catches food particles as they are about to exit.[13]
[edit] Attachment to substrate
Most modern species attach to hard surfaces by means of a cylindrical pedicle ("stalk"), an extension of the body wall. This has a chitinous cuticle (non-cellular "skin") and protrudes through a opening in the hinge.[10] However, some genera such as the inarticulate Crania and the articulate Lacazella have no pedicle, and cement the rear of the "pedicle" valve to a surface so that the front is slightly inclined up away from the surface.[10]
Pedicles of inarticulate species are extensions of the main coelom, which houses the internal organs. A layer of longitudinal muscles lines the epidermis of the pedicle.[10] Members of the order Lingulida have long pedicles, which they use to burrow into soft surfaces, to raise the shells to the opening of the burrow to feed,and to retract them when disturbed.[8] However, the pedicles of the order Discinida are short and attach to hard surfaces.[10]
An articulate pedicle has no coelom, is constructed from a different part of the larval body, and has a core composed of connective tissue. Muscles at the rear of the body can straighten, bend or even rotate the pedicle. The far end of the pedicle generally has rootlike extensions or short papillae ("bumps"), which attach to hard surfaces. However, articulate brachiopods of genus Chlidonophora use a branched pedicle to anchor in sediment. The pedicle emerges from the pedicle valve, either through a notch in the hinge or, in species where the pedicle valve is longer than the brachial, from a hole where the pedicle valve doubles back to touch the brachial valve. Some species stand with the front end upwards, while others lie horizontal with the pedicle valve uppermost.[10]
[edit] Feeding and excretion
The water flow enters the lophophore from the sides of the open valves, and exits at the front of the animal. In linguids the entrance and exit channels are formed by groups of chaetae that function as funnels.[4] In other brachiopods the entry and exit channels are organized by the shape of the lophophore.[8] The lophophore captures food particles, especially phytoplankton (tiny photosynthetic organisms), and deliver them to the mouth via the brachial grooves along the bases of the tentacles.[4] The cilia of the lophophore can change direction to eject isolated partciles of indigestible matter. If the animal encounters larger lumps of undesired matter, the cilia lining the entry channels pause and the tentacles in contact with the lumps move apart to form large gaps and then slowly use their cilia to dump the lumps on to the lining of the mantle. This has its own cilia, which wash the lumps out through the gape between the valves. If the lophophore is clogged, the adductors snapped the valves sharply, which creates a "sneeze" that clears the obstructions.[8]
The mouth is at the base of the lophophore.[14] Food passes through the mouth, muscular pharynx ("throat") and oesophagus ("gullet"),[4] all of which are lined with cilia and cells that secrete mucus and digestive enzymes.[8] The stomach wall has branched ceca ("pouches") where food is digested, mainly within the cells.[4]
Nutrients are transported throughout the coelom, include the mantles lobes, by cilia.[8] The wastes produced by metabolism are broken into ammonia, which is eliminated by diffusion through the mantle and lophophore.[4] Brachiopods have metanephridia, used by many phyla to excrete ammonia and other dissolved wastes. However, brachiopods have no sign of the podocytes which perform the first phase of excretion in this process,[15] and brachiopod metanephridia appear to be used only to emit sperm and ova.[4]
The majority of brachiopods' food is digestible, with very little solid waste to be removed.[16] Some inarticulate brachiopods have a U-shaped digestive tract ending with an anus that eliminates solids from the front of the body wall.[14] Other inarticulate brachiopods and all articulate brachiopods have a curved gut that ends blindly, with no anus.[4] These animals bundle solid waste with mucus and periodically "sneeze" it out, using sharp contractions of the gut muscles.[8]
[edit] Circulation and respiration
The lophophore and mantle are the only surfaces that absorb oxygen and eliminate carbon dioxide. Oxygen seems to be distributed by the fluid of the coelom, which is circulated through the mantle and driven either by contractions of the lining of the coelom or by beating of its cilia. In some species oxygen is partly carried by the respiratory pigment hemerythrin, which is transported in coelomocyte cells.[4]
Brachipods also have colorless blood, circulated by a muscular heart which lies in the dorsal part of the body above the stomach.[4] The blood passes through vessels that extend to the front and back of the body, and branch to organs including the lophophore at the front and the gut, muscles, gonads and nephridia at the rear. The blood circulation seems not to be completely closed, and the coelomic and blood fluids must mix to a degree.[8] The main function of the blood may be to deliver nutrients.[4]
[edit] Nervous system and senses
The "brain" of adult articulates consists of two ganglia, one above and the other below the oesophagus. Adult inarticulates have only the lower ganglion.[17] From the ganglia and the commissures where they join, nerves run to the lophophore, the mantle lobes and the muscles that operate the valves. The edge of the mantle is probably the greatest concentration of sensors. Although not directly connected to sensory neurons, the mantle's chaetae probably send tactile signals to receptors in the epidermis of the mantle. Many brachiopods closing their valves if shadows apear above them, but the cells responsible for this are unknown. Some brachiopods have statocysts, which detect changes in the animals' balance.[4]
[edit] Reproduction and lifecycle
Adults of most species are of one sex throughout their lives. The gonads are masses of developing gametes ( ova or sperm), and most species have four gonads, two in each valve.[4] Those of articulates lie in the channels of the mantle lobes, while those of inarticulates lie near the gut.[8] Ripe gametes float into the main coelom and then exit into the mantle cavity via the metanephridia, which open on either side of the mouth. Most species release both ova and sperm into the water, but females of some species keep the embryos in brood chambers until the larvae hatch.[4]
The cell division in the embryo is radial (forms stacks of rings directly above each other[18]), holoblastic (cells are separate, although adjoining[18]) and regulative (the type of tissue into which a cell develops is controlled by interactions between adjacent cells, rather than rigidly within in each cell[18]). While some animals develop the mouth and anus by deepening the blastopore, a "dent" in the surface of the early embryo, the blastopore of brachiopods closes up, and their mouth and anus develop from new openings.[4]
The larvae of inarticulates swim as plankton for some time, and are miniature adults, with valves, mantle lobes, a pedicle that coils in the mantle cavity, and a miniature lophophore, which is used for both feeding and swimming[4] – except that Craniids have no pedicle.[8] As the shell becomes heavier, the juvenile sinks to the bottom and becomes a sessile adult.[4] The larvae of an articulate species live only on yolk, and remain only among the plankton for a little over a day. This type of larva has a ciliated frontmost lobe that becomes the body and lophophore, a rear lobe that becomes the pedicle, and a mantle like a skirt, with the hem towards the rear. On metamorphosing into an adult, the pedicle attaches to a surface, the front lobe develops the lophophore and other organs, and the mantle rolls up over the front lobe and starts to secrete the shell.[4]
[edit] Taxonomy
| Classes | Inarticulata | Articulata | |||
|---|---|---|---|---|---|
| Orders | Lingulida[4] | Discinida[4] | Craniida[4] | Terebratulida[4] | Rhychonelida[4] |
| Hinge | No teeth | Teeth and sockets | |||
| Anus | On front of body, at end of U-shaped gut | None | |||
| Pedicle | Contains coelom with muscles running through | No pedicle | No coelom, muscles where joins body | ||
| Long, burrows | Short, attached to hard surfaces | None, cemented to surface | Short, attached to hard surfaces[6] | ||
| Periostracum | Glycosaminoglycans and chitin | Chitin | Proteins | ||
| Primary (middle) mineralized layer of shell | Glycosaminoglycans and apatite (calcium phosphate) | Calcite (a form of calcium carbonate) | |||
| Inner mineralized layer of shell | Collagen and other proteins, chitinophosphate and apatite (calcium phosphate) | Calcite | Proteins and calcite | ||
| Chetae round opening of shells | Yes[6] | No[6] | Yes[6] | ||
| Coelom fully divided | Yes[6] | No[6] | Yes[6] | ||
In additional to the "traditional" classification shown above, Peter Ax presents two other major approaches:[6]
- The Craniida are grouped with the Articulata as Calciata (calcareous animals), as both groups have calcite shells, while the Lingulata (Inarticulata excluding the Craniida) have shells of chitin and calcium phosphate.
- The Craniida are distinguished from all the other groups by having no chetae ("hairs" round the opening of the shells), and by having a coelom that is fully separated into a mesocoel (middle cavity) and metacoel (rear cavity).
[edit] Ecology
Brachiopods maximum consumption is low, and their minimal is not measurable. Members of some genera have survived for a year without food, although they lost a lot of weight.[3]
[edit] General description
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 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 38.5 cm (about 15 in) in width.
[edit] Valves
Brachiopods have two valves. Brachiopod valves are upper and lower rather than left and right and are designated respectively the pedical valve and brachial valve. The pedical valve is attached to the pedical and has the adjustor muscles for positioning. The brachial valve houses the brachidia, supports for the lophophore. Brachiopods, like ammonites, are often illustrated, especially in the professional literature, upside down with the pedical valve shown ventral and the brachial valve shown dorsal; not true in nature. (MLF p 203–204)
[edit] Articulate Shell Structure
Articulate brachiopod shells are composed of calcium carbonate. There is an outer laminar layer and an inner fibrous layer (MLF p 204) that slopes toward the laminar layer in the direction of the shell margin. The fibrous layer contains openings known as pallial sinuses, which in life contain mantal material. In fossil forms the pattern of pallial sinuses is diagnositic in dertermining different genera.
Articulate shells are either impunctate, punctate, or pseudopunctate. Impuctate shells are solid, except for pallial openings in the fibrous layer. Punctate shells are perforated by tubules or pores, known puncti (sing. punctum) that extend from the inner side of the fibrous layer, almost to the outer side of the laminar layer. Pseudopunctate shells have rod-loke bodies of structureless calcite in the fibrous layer that may weather more readily, leaving openings that may be confused for puncti. (MLF p 203–204 )
[edit] Evolutionary history
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.[19] 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.
The origin of the brachiopods is unclear; two hypotheses suggest how a bivalved lifestyle could have emerged.
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 Lophophorata.
The brachiopods evolved in the lower Cambrian, and became particularly numerous in shallow water habitats during the Ordovician & Silurian, in some cases forming whole banks in much the same way as bivalves (such as mussels) do today. In some places, large sections of limestone 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 extinctions.
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, a famous paper by Stephen Jay Gould suggested that the rise in bivalves which accompanied the downfall of the brachiopods was nothing more than coincidence - the two lineages were like "ships that pass in the night".[20] The greatest successes for the bivalves have been in habitats that 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.
[edit] Classification
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. This article follows Williams, Carlson & Brunton (2000),[21] who subdivide Brachiopoda into three subphyla, eight classes, and 26 orders. These categories are believed to be approximately monophyletic. Brachiopod diversity declined significantly at the end of the Paleozoic. Only five orders in three classes include forms that survive today, a total of between 300 and 500 extant species. In their zenith during the mid-Silurian Period, 16 orders of brachiopods coexisted.
| Brachiopod Taxonomy Extant taxa in green, extinct taxa in grey |
|||
| Subphyla | Classes | Orders | Extinct |
|---|---|---|---|
| Linguliformea | Lingulata | Lingulida | no |
| Siphonotretida | Ordovician | ||
| Acrotretida | Devonian | ||
| Paterinata | Paterinida | Ordovician | |
| Craniformea | Craniforma | Craniida | no |
| Craniopsida | Carboniferous | ||
| Trimerellida | Silurian | ||
| Rhynchonelliformea | 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 | ||
[edit] Comparison with bivalves
While brachiopods superficially resemble bivalve molluscs, the similarities are purely a product of convergent evolution; brachiopods and bivalves belong to different phyla and thus 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 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.
Furthermore, brachiopod shells are made of different minerals. While bivalves construct their shells from aragonite, Linguliformea use apatite, and the Rhynchonelliformea and Craniiformea produce calcite shells.[22]
[edit] Gallery
 Brachiopod fossils are often found in dense assemblages, such as these specimens of the Ordovician species Dalmanella meeki. |
 Brachiopod morphology |
 A Carboniferous brachiopod Neospirifer condor, from Bolivia. The specimen is 7 cm across. |
 Rhynchotrema dentatum, a rhynchonellid brachiopod from the Cincinnatian (Upper Ordovician) of southeastern Indiana. |
 A Devonian spiriferid brachiopod from Ohio that served as a host substrate for a colony of hederellids. The specimen is 5 cm wide. |
 Syringothyris sp.; a spiriferid brachiopod from the Logan Formation (Lower Carboniferous) of Wooster, Ohio (internal molds). |
 Petrocrania brachiopods attached to a strophomenid brachiopod; Upper Ordovician of southeastern Indiana. |
[edit] References
- ^ Easton, W.H. (1960). Invertebrate Paleontology. New York:: Harper and Brothers.
- ^ Trumble, W., and Brown, L. (2002), "Cnida", Shorter Oxford English Dictionary, Oxford University Press
- ^ a b c Cohen, B.L. (2006), "Brachiopoda", Encyclopedia of Life Sciences, John Wiley & Sons, Ltd., doi:
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 821–829. ISBN 0030259827.
- ^ "Apatite" is stricly defined in terms of its structure rather than chemical composition. Some forms contain calcium phosphate and others have calcium carbonate. See see Cordua, W.S.. "Apatite Ca5(PO4, CO3)3(F, Cl, OH) Hexagonal". University of Wisconsin. http://www.uwex.edu/wgnhs/Mineral%20Index/Minerals/apatite.htm. Retrieved 23 Oct 2009.
- ^ a b c d e f g h i j Ax, P. (2003). "Brachiopoda". Multicellular Animals: Order in Nature - System Made by Man. Multicellular Animals: A New Approach to the Phylogenetic Order in Nature. 3. Springer. pp. 87-93. ISBN 3540001468. http://books.google.co.uk/books?id=MKUab3WegL0C&pg=PA92&dq=discinida+discinid#v=onepage&q=&f=false. Retrieved 2 Nov 2009.
- ^ Parkinson, D.; Curry, G.B., Cusack, M., and Fallick, A.E. (2005). "Shell structure, patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shell". Chemical Geology (Elsevier) 219 (1-4): 193-235. doi:.
- ^ a b c d e f g h i j k l m n Doherty, P.J. (2001). "The Lophophorates". in Anderson, D.T.. Invertebrate Zoology (2 ed.). Oxford University Press. pp. 356–363. ISBN 0195513681.
- ^ Peck, L.S. (2007). "Body volumes and internal space constraints in articulate brachiopods". Lethaia (Wiley InterScience) 25 (4): 383-390. doi:.
- ^ a b c d e f Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 829–845. ISBN 0030259827.
- ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 817–821. ISBN 0030259827.
- ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 817. ISBN 0030259827.
- ^ Riisgård, H.U.; Nielsen, C., and Larsen, P.S. (2000). "Downstream collecting in ciliary suspension feeders: the catch-up principle". Marine Ecology Progress Series 207: 33–51. http://www.int-res.com/articles/meps/207/m207p033.pdf. Retrieved 12 Sept 2009.
- ^ a b Cohen, B.L.; Holmer, L. E. and Lüter, C. (2003). "The brachiopod fold: a neglected body plan hypothesis". Palaeontology (Wiley) 46 (1): 59-65. doi:. http://eprints.gla.ac.uk/2920/1/Cohen_2920.pdf. Retrieved 2 Nov 2009.
- ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Introduction to Bilateria". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 212–214. ISBN 0030259827.
- ^ Cowen, R. (2000). "Invertebrate paleontology". History of life (3 ed.). Wiley-Blackwell. pp. 408. ISBN 0632044446. http://books.google.co.uk/books?id=qvyBS4gwPF4C&pg=PA408&dq=brachiopod+oxygen&lr=#v=onepage&q=brachiopod%20oxygen&f=false. Retrieved 2 Nov 2009.
- ^ Nielsen, C. (2005). "Larval and adult brains". Evolution & Development (Wiley InterScience) 7 (5): 483-489. doi:.
- ^ a b c Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Introduction to Bilateria". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 216–217. ISBN 0030259827.
- ^ Ushatinskaya, G.T. 2008. Origin and dispersal of the earliest brachiopods. Paleontological Journal 42 (8): 776-791. [1]
- ^ Gould, S. J.; Calloway, C. B. (01 Oct 1980). "Clams and Brachiopods — Ships that Pass in the Night". Paleobiology 6 (4). doi:. ISSN 00948373.
- ^ a b Williams; Carlson; Brunton (2000), Treatise on Invertebrate Paleontology
- ^ Balthasar, Uwe (August 2009). "The Evolution of Shell Composition in Brachiopods". in Smith, Martin R.; O'Brien, Lorna J.; Caron, Jean-Bernard. International Conference on the Cambrian Explosion (Walcott 2009). Abstract Volume. Toronto, Ontario, Canada: The Burgess Shale Consortium. 31st July 2009. ISBN 978-0-9812885-1-2. http://burgess-shale.info/abstract/balthasar.
- Williams, A; Carlson, S.J., and Brunton, C.H.C. (2000). "Brachiopod classification". in Williams, A. et al.. Brachiopoda (revised). 2. Part H of Kaesler, R.L., ed. Treatise on Invertebrate Paleontology. Boulder, Colorado and Lawrence, Kansas: Geological Society of America and The University of Kansas. ISBN 0-8137-3108-9.
- MLF (Moore, Lalicker and Fischer); Invertebrate Fossils, McGraw-Hill Book, 1952
[edit] External links
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Wikimedia Commons has media related to: Brachiopoda |
- UC-Berkeley Museum of Paleontology
- Palaeos Brachiopoda
- BrachNet
- Information from the Kansas Geological Survey
- site of R.Filippi
- Brachiopoda World Database
[edit] See also
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