Littorinimorph Snails

Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails (marine species), but also including some freshwater snails (limnic species) and land snails (terrestrial species).

Previously, the Linnaean taxonomy used in the taxonomy of the Gastropoda by Ponder & Lindberg (1997) ranked like this: subclass Orthogastropoda, superorder Caenogastropoda, order Sorbeoconcha, suborder Hypsogastropoda, infraorder Littorinimorpha.

The order Littorinimorpha contains many gastropod families that were formerly placed in the order Mesogastropoda, as introduced by J. Thiele in his work from 1921. Evidence for this group being monophyletic is scanty. In 2003, E. E. Strong suggested using only Neogastropoda as a clade within the clade Hypsogastropoda, and to include the unresolved superfamilies of the Hypsogastropoda within the Littorinimorpha.

Littorinimorpha is paraphyletic, as the superfamilies Calyptraeoidea, Capuloidea, Cypraeoidea, Ficoidea, Tonnoidea, and Velutinoidea are members of the clade Latrogastropoda and are more closely related to neogastropods than other littorinimorphs. As such, "littorinimorph" has been considered an informal term for non-neogastropod hypsogastropods. It is possible that a restricted concept of Littorinimorpha that excludes latrogastropods is monophyletic, but this is uncertain. There are some consistent clades within Littorinimorpha, such as a clade uniting Littorinidae, Naticoidea, and Pterotracheoidea, and a clade uniting Rissooidea, Truncatelloidea, and Vanikoroidea.