A new genus and species of turtle blood fluke (Digenea: Schistosomatoidea) from the Mekong snail-eating turtle, Malayemys subtrijuga (Schlegel & Müller) (Testudines: Geoemydidae) in Vietnam, with a reassessment of related Asiatic turtle blood flukes and molecular phylogeny.

Platt sinuosus Roberts & Bullard n. g., n. sp. (type-species) infects the kidney and mesenteric blood vessels of Mekong snail-eating turtles, Malayemys subtrijuga (Schlegel & Müller), in the Mekong River Basin. Species of Platt Roberts & Bullard n. g. are unique by the combination of having a papillate ventral sucker, vasa efferentia that are dorsal to the gonads, a massive cirrus-sac that is directed anteriad or laterad, and a vitellarium that surrounds the intestinal caeca. The new species resembles Platt ocadiae (Takeuti, 1942) Roberts & Bullard n. comb. but differs from it by having an external seminal vesicle that overlaps with or is immediately posterior to the level of the ventral sucker. Seven species previously of Hapalorhynchus Stunkard, 1922 are reassigned herein to Platt: P. odhnerensis (Mehra, 1933) Roberts & Bullard n. comb.; P. yoshidai (Ozaki, 1939) Roberts & Bullard n. comb.; P. ocadiae; P. oschmarini (Belous, 1963) Roberts & Bullard n. comb.; P. sutlejensis (Mehrotra, 1973) Roberts & Bullard n. comb.; P. synderi (Platt & Sharma, 2012) Roberts & Bullard n. comb.; and P. tkachi (Platt & Sharma, 2012) Roberts & Bullard n. comb. A dichotomous key to Platt spp. is provided. Hapalorhynchus sheilae (Mehrotra, 1973) Bourgat, 1990 and Hapalorhynchus mica (Oshmarin, 1971) Bourgat, 1990 are considered as species inquirendae, and Hapalorhynchus indicus (Thapar, 1933) Price, 1934 and Hapalorhynchus macrotesticularis (Rohde, Lee, & Lim, 1968) Brooks & Sullivan, 1981 are considered as species incertae sedis. Phylogenetic analysis of the large subunit rDNA (28S) showed P. sinuosus and P. snyderi to be sister taxa distinct from a monophyletic Hapalorhynchus and Coeuritrema platti Roberts & Bullard, 2016.