Phylogenetic relationships and classification of Solaropsidae (Gastropoda: Stylommatophora)

The classification of terrestrial sundial snails has a long and contentious history; they have been diversely classified in Camaenidae, Pleurodontidae, Polygyridae, and also in their own family, Solaropsidae. Two genera have been recently removed from Solaropsidae (Polygyratia Gray, 1847 and Ridleya Ancey, 1901), but the status of its 3 remaining genera (Solaropsis H. Beck, 1837, Olympus Simone, 2010, and Psadara K. Miller, 1878) is still uncertain. We have sequenced 4 mitochondrial and nuclear markers of species belonging to those 3 genera and included them in a phylogenetic framework of all helicoid snails (Sagdoidea and Helicoidea). Our analysis supports a monophyletic Solaropsidae within Sagdoidea, as well as its internal division into Solaropsinae and Caracolinae. Solaropsis and Psadara are both paraphyletic and include the monotypic Olympus. Thus, we consider the latter 2 genera synonymous with Solaropsis. We also present a summary of the fossil record of the family, excluding from it the genus Hodopoeus Pilsbry & Cockerell, 1945 (now classified in Labyrinthidae) and discussing the paleobiogeographic history of Sagdoidea and of early branches of Helicoidea. Finally, Epiphragmophoridae (formerly a subfamily of Xanthonychidae) is supported as a distinct family-level clade within Helicoidea.