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Recognising brachiopods
Brachiopods are sea animals with two shells, or valves. Brachiopods can be confused with bivalves, but the way to distinguish them is to look at the
line that goes through the valves. Brachiopods are symmetrical about this line, bivalves are generally not. Most brachiopods also have strongly bulbous valves. Brachiopods open and close the valves with two sets of muscles.
When they die, the withered muscles hold the valves shut, so that it is usual to find brachiopods as a complete shell of two connected valves. Bivalves, on the other hand, open up when the animal dies, and the valves become detached.
It is, therefore, common to find clam valves separately, and uncommon to find them together.
(Below) Rhynconellid brachiopod from above, from the side and slightly above, and from the back.
(Below) Terebratulid brachiopod from above, the side, and below.
Symmetry along both ventral and dorsal valves
Not symmetrical between valves when seen from the side
The pedicle went through a hole in the ventral valve. This shows as a depression in the fossil.
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