Molecular phylogeny and morphological evolution of the Chinese land snail Cathaica Mollendorff, 1884 (Eupulmonata: Camaenidae) in Shandong Province, China

Cathaica is a genus of bradybaenid land snails occurring in China and is widespread in Shandong Province. Here we re-describe three species, C. pyrrhozona, C. fasciola and C. leei, and describe two new species, Cathaica fohuiensis Zhang sp. nov. and Cathaica multicostata Zhang sp. nov.. Geometric morphometric analyses demonstrate that C. pyrrhozona, C. fasciola, C. leei and C. fohuiensis are conchologically similar. Based on differences in their genitalia and molecular data, we consider C. pyrrhozona and C. fasciola to be distinct species. This re-establishes C. pyrrhozona as the type species of Cathaica. Cathaica leei can be distinguished based on its plate spiral whorl and wide umbilicus. The new species C. fohuiensis, with a conical shell and expanded vaginal base, can be distinguished from other Cathaica species based on morphological criteria and is robustly supported in the phylogenetic tree. The other new species, C. multicostata, possesses a strongly ribbed discoid shell and exhibits mucous glands that cluster tightly with the vagina. It is robustly supported in the phylogenetic tree and is the sister taxon to the other Cathaica species. Based on morphological characters and our molecular tree, Pliocathaica, represented here by P. buvigneri, P. pulveratricula and P. gansuica, is not monophyletic.