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
Modern brachiopods range from 1 to 100 millimetres long, and most species are about 10 to 30 millimetres Each has two valves (shell sections) which are biomineralized.
The brachial valve bears on its inner surface 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.The brachial and pedicle valves are often call the dorsal ("upper") and ventral ("lower"), 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. 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 lingulids, which burrow into the seabed, have valves that are smoother, flatter and of similar size and shape.
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