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Recent conceptual and practical advances in phylogenetic species delimitation have enabled progressively robust biodiversity studies. Delimiting species in widespread taxa is an intriguing problem; the edible operculated land snail Cyclophorus volvulus (Müller, 1774) is a good example since it shows a high degree of shell and color variation along with a widespread distribution throughout Thailand. Taxonomic boundaries for C . volvulus were examined and clarified using a combined morphological and phylogenetic approach, the latter of which was based on both nuclear and mitochondrial gene sequences. Moreover, three species delimitation analyses were applied: Poisson tree processes (PTP), automatic barcode gap discovery (ABGD), and generalized mixed Yule-coalescent (GMYC). All phylogenetic trees revealed that C . volvulus was polyphyletic and comprised of three clades that coincided with their geographic distribution. The three species delimitation analyses concurred with the phylogenies and formed at least three groups. According to the results, C . volvulus s.l., as currently recognized, consists of three distinct species in Thailand: C . volvulus s.s., C . occultus sp. nov., and C . borealis sp. nov., which are described herein. Moreover, several of these highly distinct C . volvulus evolutionarily significant units (ESU) are likely to require urgent conservation attention.

The endemic terrestrial Crown Snail from Southern Thailand formerly in Macrochlamys Gray, 1847 is now described as Taphrenalla Pholyotha & Panha gen. nov., based on comparative morphology and molecular data. Overall, eleven Taphrenalla species are now recognized, including two nominal species: T. asamurai and T. diadema. A total of nine new species are proposed: T. alba sp. nov., T. conformis sp. nov., T. corona sp. nov., T. dalli sp. nov., T. incilis sp. nov., T. macrosulcata sp. nov., T. parversa sp. nov., T. pygmaea sp. nov. and T. zemia sp. nov. The molecular phylogeny constructed from the mitochondrial cytochrome oxidase c subunit I (COI) and 16S rRNA gene fragments plus the nuclear 28S rDNA gene fragments revealed that Taphrenalla gen. nov. is monophyletic with a well-supported clade. The diagnostic characters of Taphrenalla gen. nov. are the shell sculpture with several radial grooves, body with well-developed colourful stripes running from the head to tail, and genitalia similar to Macrochamys but with an un-coiling epiphallic caecum. The spermatophore has one or two spines near the sperm sac and a spineless tail.