An outline of cassoidean phylogeny (Mollusca, Gastropoda)

The phylogeny of cassoidean gastropods is reviewed, incorporating most of the biological and palaeontological data from the literature. Several characters have been checked personally and some new data are presented and included in the cladistic analysis. The Laubierinioidea, Calyptraeoidea and Capuloidea are used as outgroups. Twenty-three apomorphies are discussed and used to define cassoid relations at the subfamily level. A classification is presented in which only three families are recognised. The Ranellidae contains the subfamilies Bursinae, Cymatiinae and Ranellinae. The Pisanianurinae is removed from the Ranellidae and attributed to the Laubierinioidea. The Cassidae include the Cassinae, Oocorythinae, Phaliinae and Tonninae. The Ranellinae and Oocorythinae are both paraphyletic taxa and are considered to represent the stem-groups of their families. The third family, the Personidae, cannot be subdivided into subfamilies and for anatomical reasons probably evolved from the same Early Cretaceous gastropod ancestor as the Ranellidae. The Cassidae (Oocorythinae) appears to have branched off from the Ranellidae (Ranellinae) during the Late Cretaceous. The first significant radiation of the Ranellidae/Cassidae branch took place in the Eocene. The Tonninae represents the youngest branch of the phylogenetic tree.