Brachiopods

Ancient sea shells

Brachiopods are marine animals that have existed for around 550 million years. They have a pair of shells, which they can clamp shut for protection, or open slightly to filter the water for food.  Although brachiopods once dominated the sea floor, most are now extinct – only about 30 species survive today

The name comes from the Greek words ‘brachio’ and ‘poda’, meaning ‘arm’ and ‘foot’. The arm is a hard structure inside the shell that supports an organ covered in fine hairs. These hairs filter the water to find food. The foot is a fleshy stalk that attaches it to the sea floor.

Sorting sea shells

Although they look like modern sea shells (called bivalves), brachiopods are very different. They are symmetrical from the mid-line, whereas bivalve shells are more asymmetric or lopsided. Brachiopods have one shell larger than the other and that larger shell has a small hole in the ‘point’ or umbo, through which the stalk or pedicle, extended.

A symmetrical brachiopod shell (above) compared with a bivalve shell (below) which is asymmetrical or lopsided and does not have a hole or pedical opening.
A symmetrical brachiopod shell (above) compared with a bivalve shell (below) which is asymmetrical or lopsided and does not have a hole or pedical opening.
Bivalve shell
Bivalve shell

Jurassic Coast brachiopods

There are several different types of brachiopod but the most common along the Jurassic Coast are smooth Terebratulids (below right) and ribbed Rhynchonellids (below left).