Rediscovering the dancing semislug genus Cryptosemelus Collinge, 1902 (Eupulmonata, Ariophantidae) from Thailand with description of two new species.

Knowledge of Thai semislugs remains scarce, especially the dancing semislug genus Cryptosemelus. Prior to the present study, only a single species has been recognized with little available information. To address this knowledge gap, we surveyed for semislugs in western and southern Thailand, which yielded three species belonging to the genus Cryptosemelus. The little-known type species C.gracilis is redescribed herein, including a comparison with the type specimens. Two additional species, C.betarmon sp. nov. and C.tigrinus sp. nov., are described as new to science. All three species are characterized by differences in their genital anatomy, especially with respect to anatomical details of the penis, epiphallus, and spermatophore. In addition, C.tigrinus sp. nov. differs from C.gracilis and C.betarmon sp. nov. in the mantle color pattern.