Kongim B.Mahidol University2023-07-172023-07-172023-01-01Tropical Natural History (2023) , 242-25015139700https://repository.li.mahidol.ac.th/handle/20.500.14594/87852Chamberlainia somsakpanhai sp. nov., the largest freshwater bivalve (Unionidae) in the Mekong Basin, is described using morphological characters and molecular analysis. The new species differs from its congeners by having an ovate shell outline and obtuse and distinct sub-biangulate posterior margin. A multi-locus phylogenetic tree (mitochondrial COI and 16S, and nuclear 28S genes) recognized the new species along with other two members of the genus, namely C. hainesiana and C. duclerci. Average genetic divergence between the new species and its congeners is 13.8–14.1% by an uncorrected COI p-distance.Agricultural and Biological SciencesArticleSCOPUS2-s2.0-85163289565