Testing Relationships Among the Vetigastropod Taxa: A Molecular Approach

Abstract

Identifying the unambiguous members of Vetigastropoda and understanding the relationships among its families has been challenging. This study investigates the internal relationships among putative members of Vetigastropoda sensu lato (Fissurelloidea, Haliotoidea, Lepetelloidea, Lepetodriloidea, Pleurotomarioidea, Scissurelloidea, Seguenzioidea, Trochoidea, Angarioidea, Phasianelloidea, Neomphaloidea and Cocculinoidea) in a molecular phylogeny utilizing nearly 6kb of molecular data from up to five nuclear and mitochondrial genes. Single-step parsimony-based and two-step maximum-likelihood analyses are employed as phylogenetic methods to analyse the data. Sequence data from all vetigastropod groups are included and in order to overcome shortfalls of previous vetigastropod analyses resulting from the under-sampling of outgroups, this study also includes broad outgroup representation. Fissurelloidea, Haliotoidea, Lepetodriloidea, Scissurelloidea, Seguenzioidea, Trochoidea, Angarioidea and Phasianelloidea formed a clade identified as Vetigastropoda sensu stricto united by morphological synapomorphies such as the presence of bursicles and epipodial sense organs. In contrast, Neomphalina, Cocculinoidea and Pleurotomarioidea fell outside Vetigastropoda s. s., indicating a need to reexamine the classification of these clades as vetigastropods.