Etymology

Brachiopod :

from the Greek : brakhion - arm,
podos - foot

Natural history of animals without vertebrae

The phylum of Brachiopoda has existed since the lower Cambrian period. But, it was only in Devonian that they had their most significant radiation. From the Carboniferous onwards, the number of species falls strongly, until a new maximum during the Jurassic. With the development of other marine organisms, such as gastropods or bivalves, brachiopods were continually regressing or moving to particular environments, as to the oceanic depths for example. Although resembling Lamellibranchia molluscs, brachiopods form a separate phylum, most closely related to the Bryozoa and Phoronida. Their shell is composed of two valves each with a different form and size: a smaller dorsal valve and a larger ventral valve. The ventral valve is provided with a hook more or less bent and perforated. The opening in the posterior end of the hook, through which protruded a fleshy stalk (pedicle), a kind of foot with which the animal generally lives fixed on the substrate, ventral valve downwards, is called foramen. These marine creatures aspire water and filter it using their lophophore, a filter-feeding apparatus shaped in a kind of arm or ribbon, to extract the nutritive oxygen and elements which allow them to live. Two classes of brachiopods are also distinguished: the more primitive Inarticulata, of which well known examples the lingules, and the Articulata the most advanced brachiopods (Rhynchonellida, Terebratulida, Spiriferida...). Among the Inarticulata, the two valves are joined together only by muscles, the Articulata shells have a more sophisticared teeth and socket along the hinge.

Conchyliology : the study of shells.

Bryozoa : marine invertebrate with external horned or calcareous envelope, living in colonies.

Phoronida : "horseshoe worms"

Phylum : taxonomic category, includes one or more classes