Phylogeny of the Caenogastropoda (Mollusca), based on comparative morphology

Abstract

The systematics, classification and phylogeny of the Caenogastropoda are revised based on an analysis of the morphology of representatives of all branches. The basis of this work is the detailed examination of the morphology of 305 species, most of which are reported on in detail elsewhere. Representatives of most caenogastropod families were included (comprising 270 species), and 35 outgroup taxa. A phylogenetic analysis based upon 676 morphological characters, with 2291 states (1915 of which are apomorphic states), is presented. The characters comprise every organ system and many are discussed in detail. The polarization is based on a pool of non-caenogastropods, comprising 27 representatives of Heterobranchia, Neritimorpha, Vetigastropoda, Cocculiniformia and Patellogastropoda. Additionally, eight representatives of other classes are also included. The root is based on the representative of Polyplacophora. A few characters were included in order to organize the outgroups, to find the position of Caenogastropoda among them, and to find the synapomorphies of Caenogastropoda. A strict consensus cladogram of the 48 most parsimonious trees (Fig. 20; length of 3036, CI = 51 and RI = 94) is presented, a synopsis of which is: ((((((Cyclophoroidea2 (Ampullarioidea5 (Viviparoidea15 (Cerithioidea19 (Rissooidea41 (Stromboidea47 (Calyptraeoidea67 (Naticoidea97 (Cypraeoidea118 (Tonnoidea149 (Conoidea179 (Cancellarioidea222 – Muricoidea212)))))))))))) HeterobranchiaV) Neritimorpha U) VetigastropodaL) CocculiniformiaJ) Patellogastropoda) (superscripts indicating the nodes at Fig. 20). The monophyly of the Caenogastropoda is supported by 60 synapomorphies. Based on this cladogram, the systematics, evolution and paleontology of the group are discussed, as along with comparisons with other phylogenetic studies involving Caenogastropoda, including those obtained from molecular data. The list of characters is included in Appendix 1; the matrix of characters in Appendix 2; and the list of synapomorphies of each node are presented in Appendix 3 in form of symbols. As the phylogeny obtained in this analysis has a high degree of concordance with other recent phylogenetic studies, a number of new supra-superfamiliar taxa are introduced: Siphonogastropoda (Cypraeoidea + Peogastropoda); Adenogastropoda (Naticoidea + Siphonogastropoda); Rhynchogastropoda (Calyptraeoidea + Adenogastropoda); Strombogastropoda (Stromboidea + Rhynchogastropoda); Peogastropoda (Tonnoidea + Neogastropoda); Epiathroidea (Viviparoidea + Sorbeoconcha); Hydrogastropoda (Ampullarioidea + Epiathroidea); Adenogonogastropoda (Neritimorpha + Apogastropoda) (Appendix 4).