Diversity and Phylogenetics of Freshwater Mussels (Unionidae) from Southern Thailand with the Description of One New Genus and Five New Species-Group Taxa

Southern Thailand represents a region of unique freshwater biodiversity with many endemic taxa, including a number of freshwater mussel species (Bivalvia: Unionidae). In this study, we recognize 13 taxa in the tribes Contradentini, Rectidentini, Pseudodontini (subfamily Gonideinae), and Indochinellini (subfamily Parreysiinae) that inhabit different localities in the Songkhla Lake, Tapi River, and Tha Taphao River basins. Based on the results of morphological and phylogenetic analyses, we discovered among these mussels six taxa new to science, including one genus, three species, and two subspecies. New taxonomic names are introduced here as follows: Songkhlanaia gen. nov.; S. tamodienica gen. & sp. nov.; Sundadontina plugpomenica sp. nov.; Monodontina vondembuschiana tapienica ssp. nov.; M. vondembuschiana thasaenica ssp. nov. (Pseudodontini); and Trapezoideus thachiadensis sp. nov. (Contradentini). These new taxa confirm the high conservation priority of the Southern Thai freshwater mussel fauna.