Wenlock creatures: Bivalves

Ctenodonta anglica

Some bivalves burrow in soft sediment, others rest on the seabed. Some are fixed to rocks, others bore into the solid rock. The bivalve in the image, Ctenodonta, has a smooth shell and would have burrowed into the soft reef debris.

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The reef-dwelling bivalve Lima has tentacles radiating out from its shell.

What are bivalves?

Bivalves (or bivalved molluscs) include oysters, mussels, clams and scallops, and today are some of the most common creatures to be found in shallow seawater. They have a pair of hinged calcium carbonate shells which can be opened for feeding and closed when danger threatens. They come in many different shapes and sizes, reflecting the many different lifestyles that they have adopted.

Bivalve shells can look similar to brachiopod shells, but the structure of their internal soft parts is very different.

DietMost bivalves use their gills to filter food out of the seawater.

Key facts about Wenlock bivalves

Reef dwellerBivalves were reef dwellers, living on the reef but not forming part of the Wenlock Reef structure.

Abundance through geological time

AbundanceThe earliest bivalves are found in Ordovician rocks, but the group did not become abundant until the Triassic.

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