Polished Bivalves Clam Fossil

Polished Bivalves Clam Fossil

Size:  74mm x 53mm x 29mm 

Weight:  123 gram

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Rare, beautifully and polished clam shells from Madagascar.  The region where these pieces were found produces very few of these very cool shells.

Bivalves have inhabited the Earth for over 500 million years. They first appeared in the Mid Cambrian, about 300 million years before the dinosaurs. They flourished in the Mesozoic and Cenozoic eras, and they abound in modern seas and oceans; their shells litter beaches across the globe. Some also occur in lakes and rivers. Fossil bivalves were formed when the sediment in which they were buried hardened into rock.

Most bivalves lived by filtering water-borne food particles, although some extracted nutrient directly from the sediment.

In the Mesozoic Era, the evolution of extendable tubes of soft tissue (siphons) enabled bivalves to burrow more deeply whilst keeping their food supply accessible. A special embayment of the inner shell margin (pallial sinus) allowed storage of the siphons when danger threatened.