Phylogenetic analysis of the gastropod genus Calliotropis Seguenza, 1902 (Vetigastropoda: Calliotropidae), including fossil and living species

Abstract

The taxonomic content of the genus Calliotropis and the systematic positions of the fossil species referred to this genus have been under debate because of the striking resemblance they bear to their extant counterparts in terms of general shell morphology and ornament pattern. In a recent contribution, two subgenera of Calliotropis were preliminarily distinguished and considered to be a result of ecomorphological variation translated into evolutionary changes: shallow-reef ecomorphotypes, representing the fossil species of Calliotropis (Riselloidea), and deep-water ecomorphotypes, grouping the living forms of Calliotropis (Calliotropis). However, this division of Calliotropis species was based on qualitative grounds, lacking a quantitative phylogenetic analysis sampling both modern and fossil taxa. The present research aims to comprehensively revisit this systematic scheme after a morphological delimitation of calliotropid lineages. We use a quantitative phylogenetic analysis to shed light on the evolutionary history of this group of gastropods. Our results indicate that the Mesozoic genus ‘Calliotropis’ is not monophyletic, but living species comprise a monophyletic group with a Pliocene–Recent distribution. Fossil ‘Calliotropis’ species represent a paraphyletic assemblage composed of different clades: the monophyletic Riselloidea (Cossmann) including only Jurassic species; a Palaeogene group represented by the new genus Arachnotropis gen. nov.; and a monophyletic Triassic group that matches the content of the previously described genus Trochonodus Nützel et al., 2003. The genus Ambercyclus Ferrari et al., 2014 is monophyletic and also related to the above-mentioned taxa.