What are bivalves?
Bivalve molluscs are among the commonest of all fossils. This group of marine and freshwater invertebrates still flourishes today and includes mussels, cockles, clams and oysters.
Bivalves, as the name implies, have shells consisting of two valves. These are joined along a hinge line - they can open to admit water, or close together tightly to protect the soft parts of the animal within. Most bivalves live on the surface of the seabed or burrow into mud or sand. Their shells are made of resistant calcium carbonate, which explains why they are so often fossilized.
Bivalve fossils are common and yet sometimes so peculiar in shape or preserved enigmatically so that they have fostered a rich folklore. Devil's toenails, Bulls' Hearts and 'Osses 'Eds are some of the folklore names coined for different kinds of fossil bivalves.