Snail-eating turtles (Malayemys spp.) are freshwater turtles native to mainland Southeast Asia. Three snail-eating turtle species (Malayemys khoratensis, Malayemys macrocephala, and Malayemys subtrijuga) were previously reported in Thailand. Before the present study, information on the distribution of snail-eating turtles in northeastern and eastern Thailand was limited, and a question arose regarding the distribution range of the new species, Malayemys khoratensis. From 2018 to 2020, we surveyed and collected data on the morphological traits of 109 snail-eating turtles along with 60 blood samples from 23 out of 27 provinces across northeastern and eastern Thailand. We found that both M. khoratensis and M. subtrijuga occur in northeastern Thailand. The distribution of M. khoratensis is in the Chi River Basin and upper Mun River Basin to the Mekong River. while the distribution of M. subtrijuga is from the lower Mun River to the Mekong River. Malayemys macrocephala occur in eastern Thailand and were found in 2 large provinces (Nakhon Ratchasima and Udon Thani) in northeastern Thailand. Based on morphological characteristics known to distinguish these species, 28 of the sampled individuals from areas in lower Mun River basin could not be assigned to any of the 3 species. Therefore, we reconstructed the phylogenetic relationships of 26 of these samples as well as other samples from known species based on 2 mitochondrial genes (Cyt b and ND4). Results based on mtDNA data indicated that the turtles in the unknown group belonged to 1 of the 3 clades corresponding to M. khoratensis, M. macrocephala, and M. subtrijuga. This result confirms that the unknown group does not represent a novel species within the genus Malayemys. However, it also indicates a discordance between the genetic and morphological characteristics of the turtles, highlighting the complexity of species identification within the genus Malayemys.

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