Tonnidae

Tonnidae
A shell of Tonna tankervillii (Hanley, 1860)
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
(unranked):	clade Caenogastropoda clade Hypsogastropoda clade Littorinimorpha
Superfamily:	Tonnoidea
Family:	Tonnidae Suter, 1913

The Tonnidae are a family of medium-sized to very large sea snails, known as the tun shells. These are marine gastropod molluscs in the clade Littorinimorpha. The name "tun" refers to the snails' shell shape which resembles wine casks known as "tuns". While the shells are thin, they are also strong. There is no operculum. They are found in all tropical seas, where they inhabit sandy areas. During the day, they bury themselves in the substrate, emerging at night to feed on echinoderms (especially sea cucumbers), crustaceans, and bivalves. Some larger species also capture fish, using their expandable probosces to swallow them whole. Females lay rows of eggs that become free-swimming larvae for several months before settling to the bottom.

In 2005, these subfamilies were recognized in the taxonomy of Bouchet & Rocroi:

Bouchet & Rocroi (2005) listed Cassidae as a synonym of Tonnidae Suter, 1913 (1825), following Riedel (1995) in this. However, later Beu (2008: 272) separated the two families. This is in agreement with the action of Thiele (1925) who placed Tonnidae and Cassidae under "Tonnacea", therefore acting as first reviser under ICZN article 24. In this respect, the World Register of Marine Species follows the opinion of Beu.

Genera and species within the family Tonnidae include:

The subfamily Cassinae has been raised to the rank of family Cassidae

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