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PALEONTOLOGICAL MUSEUM and STUDY COLLECTIONS
A. Hugh Adams Central Campus - John H. Payne Hall
BIVALVIA - View Galleries |
Cambrian - Recent |
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Bivalves have two valves, composed of calcite or aragonite that enclose the soft tissue of the mantle and other internal organs. The two valves are hinged together and are more or less symmetrical. They are similar to brachiopods in that they both have two valves, however, unlike brachiopods, bivalves have a left and right side as opposed to brachiopods which have a top and bottom and unlike brachiopods they are numerous in today's oceans. They are exclusively aquatic and some live in non-marine environments as well.
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Figure 1 Scar from attached muscle. (Lynn Curtis 2006) |
Bivalves lack a radula (toothed tongue) like the gastropods and therefore feed by siphoning and filtering small particles from the water. Some anchor themselves to substrates, bury themselves in sediment, or swim freely. The opening and closing of the valves are controlled by muscles that often leave physical scars on the valve's interior (Figure 1).
Earliest known bivalves are from the Cambrian approximately 500 million years ago (~ 500 ma), however, they did not diversify until the Ordovician (~ 460 ma). After the Permian extinctions (~ 251 ma) the bivalves moved from their nearshore habitat to the offshore shelf regions formerly inhabited by the brachiopods.
Broward College A. Hugh Adams Central Campus |
A. Hugh Adams Central Campus
3501 SW Davie Road
John H. Payne Hall, Building 7
Davie, FL 33314