Morphological and molecular evidence uncovers hidden species diversity in the leatherleaf slug genus (Systellommatophora, Veronicellidae) from Thailand.

The poorly studied leatherleaf slug genus in Thailand was carefully investigated. Members of this genus are phenotypically similar, making their identification very challenging. This study clarifies the taxonomic status of all species in Thailand by combining morphological and anatomical studies with DNA barcoding. Monophyly of all species was confirmed by analysis of the mitochondrial COI data and that all species have the acropleurocaulis type of penis. Currently, three species are recognised: , Mitchueachart & Panha, , and Mitchueachart & Panha, that are new to science. For distinct characteristics, is characterised by having a cylindrical penis and honeycomb-like glans, has a lanceolate penis with half honeycomb-like glans, and has a cylindrical penis with wavy-like glans. In addition, more detailed descriptions of the radula and genitalia of all three species and their distribution are also carefully presented, enhancing the understanding of this leatherleaf slug genus in Thailand.