Brachiopods are marine shellfish that have existed on our planet since the Early Cambrian Period and though rare now, still exist today. Brachiopods are bivalves but with bilateral symmetry but unequal valves. Most species have beautiful ornamented shells but some are smooth. The ventral side valve is called the PEDICLE VALVE and on the dorsal side, the BRACHIAL VALVE. The They attached themselves to another shell or the sea floor with a fleshy stalk called a pedicle. The average size of brachiopods is 50 mm with the smallest found being only 5 mm in size. Some species grew to sizes up to 8 cm across.
There are two fundamental types of brachiopods - the INARTICULATES and the ARTICULATES. The inarticulates lack an articulated hinge on the back where the valves meet but the articulates possess this hinge. The earliest forms were the inarticulates and the Paleozoic Age was their dominant time giving way to later periods where the articulate brachiopods became more prevalent.