Increased taxon-sampling improves generic relationships in the gastropod family Solariellidae (Gastropoda; Trochoidea)

The gastropod family Solariellidae is an emerging model for studies on snail vision, but these studies are hampered by poorly resolved relationships among genera. Here we present a new phylogeny with increased taxon-sampling and complete representation of all accepted genera, resulting in a more stable topology, and relationships that are consistent with morphology and biogeography. The systematics of three taxa, previously with uncertain generic assignment, are resolved: Zetela alphonsi Vilvens, 2002, and Solariella carvalhoi Lopes & Cardoso, 1958 are both assigned to Minolia, and ‘Bathymophila’ sp. 18 is named as Pseudobathymophila perlimata Herbert & Williams gen. et sp. nov. Two additional genera are described with six new species: Fuscomaculina Herbert, Vilvens & Williams gen. nov. (Fuscomaculina undata Herbert, Vilvens & Williams sp. nov., Fuscomaculina margaritacea Herbert, Vilvens & Williams sp. nov., Fuscomaculina pictilis Herbert, Vilvens & Williams sp. nov., Fuscomaculina salvinotata Herbert, Vilvens & Williams sp. nov., Fuscomaculina aphthonos Herbert, Vilvens & Williams sp. nov.) and Galenesia gradata Herbert & Williams gen. et sp. nov. We also reassign three South African species from Spectamen to Solariella, and Solariella tubula and Solariella lacunella to Lamellitrochus. Although most genera can now be recognized using a combination of shell and anatomical characters, separating Solariella and Spectamen remains difficult without genetic data. All genera can be clearly distinguished using molecular data, however, the generic assignment of ‘Lamellitrochus’ carinatus remains uncertain. Excluding ‘L.’ carinatus, which is sister to all other solariellids in our tree, but lacking support, our analyses suggest that solariellids originated in the central Indo-Pacific. Three genera occur in both the Indo-Pacific and Atlantic Oceans: Minolia likely originated in the Atlantic whereas Solariella and Bathymophila have Indo-Pacific origins. Based on our data and the literature, we suggest that the trochid subfamily Umboniinae competitively excludes solariellids from shallow water in the tropical and subtropical Indo-West Pacific. https://zoobank.org.urn:lsid:zoobank.org:pub:0747194D-CFA2-459C-93C5-9C8DDC4AD749