Tusk shell

Scaphopoda (; from Ancient Greek (skáphēs)'boat' and (poús)'foot') is a class of shelledmarine molluscs (invertebrates within the phylumMollusca), whose members are known as scaphopods () and commonly calledtusk shells or tooth shells. They have a worldwide distribution and are the only class of exclusively infaunal marine molluscs. Shells of species within this class range in length 0.5–18 cm (0.20–7.09 in), with Fissidentalium metivieri being the longest. Members of the order Dentaliida tend to be larger than those of the order Gadilida.

These molluscs live in soft substrates offshore (usually not intertidally). Because of this subtidal habitat and the small size of most species, many beachcombers are unfamiliar with them; their shells are not as common or as easily visible in the beach drift as the shells of sea snails and clams.

Molecular data suggest that the scaphopods are a sister group to the cephalopods, although higher-level molluscan phylogeny remains unresolved.