Photo of Rastellum oyster

Bivalves

Rastellum

Odd things, these Rastellum carinatum. Called a cockscomb oyster or denture clam for its unusual shape, these bivalves are found in Cretaceous rocks in a number of localites, including the UK. These ones are from Tulear in Madagascar, and date to about 95 million years ago.

Size varies, but roughly 7-9cm across.