A lunule (from the Latin meaning small moon or crescent moon) is an anatomical feature which is found in the exterior surface of the shells of some species of clams,

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s, as for example in the family

Veneridae The Veneridae or venerids, common name: Venus clams, are a very large family of minute to large, saltwater clams, marine bivalve molluscs. Over 500 living species of venerid bivalves are known, most of which are edible, and many of which are e ...

and in the genus '' Ascetoaxinus''. The lunule is a well-defined area near the

hinge line A hinge line is an imaginary longitudinal line along the dorsal edge of the shell of a bivalve mollusk where the two valves hinge or articulate. The hinge line can easily be perceived in these images of a mussel shell and an ark shell.Invertebrat ...

of the shell, anterior to the beaks. Website conchs.org, The Conchological Society of Great Britain and Ireland, Molluscs, Glossary, Advanced glossary of molluscan terminology, Lunule, by Steve Wilkinson, 5 November 201

Accessed 2014.12.9 Despite the name, a lunule is not always in the shape of a crescent moon. Details of the lunule are sometimes an important diagnostic feature in identifying a bivalve shell. Chionopsis intapurpurea valve view

References

{{Bivalve anatomy Bivalve anatomy Mollusc shells