The Comparative Morphology, Phylogeny and Evolution of the Gastropod Family Littorinidae

An account is given of the comparative morphology of the family Littorinidae, based on examination of 122 species, grouped into 32 subgenera. The shell, operculum and principal organ systems are described, and their phylogenetic significance assessed. A total of 53 characters, coded as 131 character states, were chosen for inclusion in a cladistic analysis of the phylogenetic relationships of the subgenera. This was performed by the program paup, using the principle of maximum parsimony. The outgroup for the analysis comprised representatives of the Pomatiasidae and Skeneopsidae. A consensus tree was obtained from cladograms with consistency indices of 0.408 (autapomorphies excluded).