Taxonomic revision and dissolution of the genus Monachoides (Gastropoda, Stylommatophora)

Monachoides is a genus of medium-sized European land snails in the family Hygromiidae. Systematics of this family was until recently based on traits of the genital system that were shown to be uninformative, resulting in revisions of classifications at the genus and family levels. Up to six species were recognized in Monachoides lately, but the inclusion of three of these species was questionable. Our phylogenetic analysis and morphological examinations show that the genus includes species previously classified in two different Hygromiidae subfamilies. After transferring three Balkan species to the unrelated genus Xerocampylaea, Monachoides emerged as a group that diversified relatively northerly, at the boundary between the Balkans and Central Europe. One species, Monachoides bacescui, is synonymized here and a previously overlooked one is redescribed, leaving only three valid species in Monachoides as currently understood: M. incarnatus, M. vicinus and M. welebitanus. These can be distinguished from other hygromiid species by their distinctive microsculpture of the shell surface, which also allows for identification of juveniles or fragmented fossil material. However, the clade comprising the three above species was found to also include the two species currently classified in Perforatella. As a result, the two genera are synonymized, with Perforatella having priority.