Poropuntius in the Chao Phraya, Mae Klong, Salween, and Tenasserim River Basins in Southeast Asia with Description of a New Species from the Mae Klong Basin in Thailand (Cypriniformes, Cyprinidae)

A new species of Poropuntius endemic to the Mae Klong River basin is described and compared to nine congeneric species in the Mae Klong, Chao Phraya, Salween, and Tenasserim River basins. Species of Poropuntius in these basins are almost universally poorly known, with information often confined to brief original descriptions. New morphological data are provided for most species, and differential comparisons are provided for all. Some species display a large amount of intraspecific variation, including ontogenetic variation related to environmental factors, and can be difficult to identify. Taxonomic revisionary studies are needed for wide-ranging species. Puntius faucis Smith, 1945, is not a species of Poropuntius, as currently assumed.