The tusk shells or scaphopods are a class of shelled marine molluscs. The scientific name of this class is Scaphopoda, meaning "shovel-footed". Shells of species within this class range from about 0.5 to 15 cm in length. Members of the Order Dentaliida are generally significantly larger than those of the Order Gadilida. These molluscslive on soft substrates offshore (usually not intertidally). Because of this subtidal habitat and the small size of most species,many beachcombersare unfamiliar with them; their shells are usually not nearly as common or as easily visible in the beach drift asthe shells of sea snails and clams. Molecular data suggests that the scaphopods are a sister group to the cephalopods, althoughhigher-level molluscan phylogeny remains somewhat unresolved.