Pentamerida

Pentamerida is an order of biconvex, impunctate shelled, articulate brachiopods that are found in marine sedimentary rocks that range from the Middle Cambrian through the Devonian.

Pentamerids are characterized by a short hinge line where the two valves articulate, inner areas above the hinge line that slope inwardly from the beak of each valve, and a well-developed spondylium on the pedical valve. The spondylim is a raised platform for muscle attachement found in the middle of the interior pedical valve, generally toward the hinge and beak. The pedical valve is the one that the pedicle, or hold-fast stalk, attaches to. The brachidia, which hold the lophophore, the ciliated feeding arms, are looped, as in the Orthida.