Brachiopod facts for kids

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Quick facts for kids Brachiopod Temporal range: Lower Cambrian–Recent PreЄ Є O S D C P T J K Pg N

Lingula anatina, an inarticulate linguliform brachiopod

Terebratalia transversa, an articulate (rhynchonelliform) brachiopod
Scientific classification
Kingdom:	Animalia
Superphylum:	Lophotrochozoa
Clade:	Lophophorata
Clade:	Brachiozoa
Phylum:	Brachiopoda Duméril, 1806
Subphyla and classes
See taxonomy
Diversity
About 100 living genera About 5,000 fossil genera

Brachiopods are a phylum of small marine shellfish, sometimes called lampshells. They are not common today, but in the Palaeozoic they were one of the most common types. They lived near the shore (littoral zone), but now they have been pushed into deeper water by competition from bivalve molluscs.

Etymology
Anatomy
Lifespan
Distribution and habitat
Interactions with other organisms
Fossil record
Interesting facts about brachiopods
Gallery
See also

Etymology

The word "brachiopod" is formed from the Ancient Greek words brachion ("arm") and podos ("foot"). They are often known as "lamp shells", since the curved shells of the class Terebratulida resemble pottery oil-lamps.

Anatomy

Modern brachiopods range from 1 to 100 millimetres (0.039 to 3.937 in) long, and most species are about 10 to 30 millimetres (0.39 to 1.18 in). Magellania venosa is the largest extant species.

They do look rather like bivalves, but their internal organisation is quite different. Their mostly calcium carbonate shells or "valves" have upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end. The front can be opened for feeding or closed for protection.

Two major groups are recognized, articulate and inarticulate. Articulate brachiopods have toothed hinges and simple opening and closing muscles, while inarticulate brachiopods have untoothed hinges and a more complex system of muscles used to fit the two halves together. In a typical brachiopod a stalk-like pedicle goes from an opening in one of the valves (the pedicle valve). It attaches the animal to the seabed but clear of silt that would block the opening.

Lifespan

Brachiopod lifespans range from three to over thirty years. The larvae of inarticulate brachiopods are miniature adults, with lophophores that enable the larvae to feed and swim for months until the animals become heavy enough to settle to the seabed. The planktonic larvae of articulate species do not resemble the adults, but rather look like blobs with yolk sacs, and remain among the plankton for only a few days before leaving the water column upon metamorphosing.

Distribution and habitat

Brachiopods are an entirely marine phylum, with no known freshwater species. Most species avoid locations with strong currents or waves, and typical sites include rocky overhangs, crevices and caves, steep slopes of continental shelves, and in deep ocean floors. However, some articulate species attach to kelp or in exceptionally sheltered sites in intertidal zones. The smallest living brachiopod, Gwynia, is only about 1 millimetre (0.039 in) long, and lives in between gravel grains. Rhynchonelliforms, whose larvae consume only their yolks and settle and develop quickly, are often endemic to an area and form dense populations that can reach thousands per meter. Young adults often attach to the shells of more mature ones. On the other hand, inarticulate brachiopods, whose larva swim for up to a month before settling, have wide ranges. Members of the discinoid genus Pelagodiscus have a cosmopolitan distribution.

Interactions with other organisms

Brachiopod shells occasionally show evidence of damage by predators, and sometimes of subsequent repair. Fish and crustaceans seem to find brachiopod flesh distasteful. In waters where food is scarce, the snail Capulus ungaricus steals food from bivalves, snails, tube worms, and brachiopods.

Among brachiopods only the lingulids have been fished commercially, and only on a very small scale. It is mostly the fleshy pedicle that is eaten. Brachiopods seldom settle on artificial surfaces, probably because they are vulnerable to pollution. This may make the population of Coptothyrus adamsi useful as a measure of environmental conditions around an oil terminal being built in Russia on the shore of the Sea of Japan.

Fossil record

At their peak in the Palaeozoic era the brachiopods occupied a number of marine ecological niches. They were among the most abundant filter-feeders and reef-builders. Many sat on the sea floor, but some swam in the jet-propulsion style of scallops.

Brachiopod fossils have been useful indicators of climate changes during the Paleozoic era. When global temperatures were low, as in much of the Ordovician, the large difference in temperature between equator and poles created different collections of fossils at different latitudes. On the other hand, warmer periods, such much of the Silurian, created smaller difference in temperatures, and all seas at the low to middle latitudes were colonized by the same few brachiopod species.

The fossil record shows that drilling predators like gastropods attacked molluscs and echinoids 10 to 20 times more often than they did brachiopods, suggesting that such predators attacked brachiopods by mistake or when other prey was scarce.

Interesting facts about brachiopods

Brachiopods are the state fossil of the U.S. state of Kentucky.
Brachiopods have a low metabolic rate.
The largest brachiopods known—Gigantoproductus and Titanaria, reaching 30 to 38 centimetres (12 to 15 in) in width—occurred in the upper part of the Lower Carboniferous.
There are about 100 to 350 Brachiopod species living; the fossil species number 12,000.
Lingula, one of the oldest genera of brachiopods, has survived from the earliest Ordovician to the present day.
The various species look very similar, and the genus is a good example of a living fossil.
Brachiopod classification is being debated by invertebrate palaeontologists.

Gallery

Brachiopod morphology
Rhynchonellid brachiopod with interior spondylium ("C" in image) visible; Roadian, Guadalupian (Middle Permian); Glass Mountains, Texas.
Pygites diphyoides (Orbigny, 1849) from the Hauterivian (Lower Cretaceous) of Cehegin, Murcia, Spain. This terebratulid is characterized by a central perforation through its valves.
Strophomenid brachiopod with attached cornulitid worm tube (Upper Ordovician, SE Indiana, USA). Brachiopod valves often serve as substrates for encrusting organisms.
Isocrania costata, Upper Maastrichtian (Upper Cretaceous), Maastricht, The Netherlands
A dense assemblage of the Ordovician species Cincinnetina meeki (Miller, 1875)
Cranaena, a terebratulid from the Middle Devonian of Wisconsin.
The Carboniferous brachiopod Neospirifer condor from Bolivia. The specimen is 7 cm across.
Tylothyris, a spiriferid from the Middle Devonian of Wisconsin
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 texta (Hall 1857), dorsal view, internal mold. Lower Carboniferous of Wooster, Ohio
Petrocrania brachiopods attached to a strophomenid brachiopod; Upper Ordovician of southeastern Indiana.
Lingula found near Ozamis City, Philippines
Barroisella, a lingulid from the Middle Devonian of Wisconsin.
Brachiopod casts in the Lock Haven Formation
Hercosestria cribrosa Cooper & Grant 1969 (Roadian, Guadalupian, Middle Permian); Glass Mountains, Texas.
Productid brachiopod ventral valve interior; Roadian, Guadalupian (Middle Permian); Glass Mountains, Texas.
Terebratella sanguinea (Leach, 1814)
Schizophoria, an orthid from the Middle Devonian of Wisconsin.
Striatochonetes, a chonetid from the Middle Devonian of Wisconsin.
Oleneothyris, a terebratulid from the Cenozoic of New Jersey
A Magellania joubini from the Ross Sea
A mass burial of brachiopods from the Logan Formation (Mississippian) in Wooster, Ohio
An Abyssothyris from the Challenger Plateau in the Pacific
A Terebratalia transversa from California