A phylogenomic framework for Vetigastropoda (Mollusca)

Abalones, turban snails, top snails, keyhole limpets and slit shells are just some of the diverse marine Vetigastropoda. With major lineages having ancient divergences in the Paleozoic Era, basal nodes in the phylogeny have been largely unresolved. Here we present the first genomic-scale dataset focused on vetigastropods, including a comprehensive sampling of taxa with all superfamilies and about half of the extant families (41 new transcriptomes, 49 total ingroup terminals). Our recovered topology is congruent among inference methods for the majority of nodes, and differs from previous studies, in which long branch attraction artifacts seem to be pervasive. The first three divergences sequentially separate Pleurotomarioidea, Seguenzioidea and Haliotoidea from remaining vetigastropods. Fissurelloidea is sister group to Scissurelloidea, Lepetodriloidea and Lepetelloidea, which all together are the sister group to Trochoidea. A methodological discordance exists in the position of Haliotidae and Fissurellidae, possibly due to a compounded effect of small sample bias derived from gene-wide partitioning. Dense sampling of trochoids and fissurellids also provides a backbone for family and subfamily-level relationships, with Tegulidae not monophyletic.