Brachiopoda

-Bivalved animals living in benthonic zone.

-Range in size from 5-200mm.

-Shells are generally unequal in size, usually symmetrical, composed of chitin or calcium carbonate, and situated ventrally and dorsally to the animal.

-The larger valve has an aperture through which a muscular stalk protrudes to anchor animal to the sub-stratum.

-The valves are opened and closed by adductor muscles, with filter feeding internal organs supported by internal structures.
-Divided into two classes:- the primitive Inarticulata which possess no hinge structure and are commonly chitinous, and the Articulata which have a hinge and are usually calcareous.

-Numerically the most important fossils in Late Permian beds.

-Found abundantly in formations around the world.

-60 genera decreased to 10 over the P-T boundary, having also suffered a slight decline through the Permian.

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