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Bivalvia (=Pelecypoda, Lamellibranchia)<br />
pair of valves (right and left valve)<br />
bilobed mantle<br />
valves articulate along a dorsal hinge line<br />
typically bilaterally symmetric (plane of symmetry passing between the valves,<br />
= commissural plane)<br />
no head<br />
prominent ventral foot<br />
known since the Early Cambrian, but diversify not prior to Ordovician<br />
but still not a very common faunal element during the Paleozoic<br />
<strong>Mollusca</strong> – systematics – Bivalvia
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