Unveiling the Diversity of the Semislug Genus Durgella Blanford, 1863 (Eupulmonata: Helicarionidae) from Thailand and Myanmar, with Description of Two New Species.

Abstract

Durgella is a terrestrial semislug genus in the family Helicarionidae and currently comprises nine species recorded from Thailand and Myanmar. Two species, D. concinna and D. rhaphiellus, have been described based only on shell information, while the taxonomy of the remaining seven species is comprehensively treated herein using comparative morphology. Revised species descriptions are given for D. levicula, D. erratica, D. siamensis, and D. libas; D. birmanica (previously placed in the Megaustenia) is moved to this genus; and two species, D. pentata Pholyotha & Panha, sp. nov. and D. nulla Pholyotha & Panha, sp. nov., are described as new to science. Based on our findings, the combination of shell characters including shape, size, aperture, and umbilicus; the number of mantle extensions; and the genitalia, especially the penis, epiphallus, and dart apparatus, can be used to distinguish these nine species. Among these nine recognised species, only D. nulla Pholyotha & Panha, sp. nov. has no dart apparatus.