A new genus and two new species of freshwater mussels (Bivalvia, Unionidae) from Sichuan, China: Overlooked cryptic endemism in the upper Yangtze River Basin

Freshwater mussels are ecologically vital but understudied in China’s Sichuan Basin, a biodiversity hotspot with significant gaps in documented diversity. Here, we conducted an investigation into the Unionidae species in Dazhou, Sichuan Province, China, and discovered two species of Unionidae that had never been recorded before. This paper confirmed through mitochondrial phylogenomic analyses that they represent new species belonging to the genera Pseudocuneopsis Huang, Dai & Wu, 2022: Pseudocuneopsis perflora H. Chen, H.-Q. Xiang, Y.-M. He, X.-C. Huang & X.-P. Wu, sp. nov. and a new genus and species: Tongchuania mingiana H. Chen, H.-Q. Xiang, Y.-M. He, X.-C. Huang & X.-P. Wu, gen. et sp. nov. Additionally, the shell morphology and soft-body anatomical characteristics of the two new species was described. These discoveries not only expand the known diversity of Unionidae in the upper Yangtze River Basin but also highlight the Sichuan Basin as a potential center of cryptic endemism. Our findings underscore the importance of combining molecular and morphological methods for uncovering hidden diversity in understudied regions and provide critical data for the conservation of China’s imperiled freshwater mussel fauna.