Serpentoanisocladium sinense n. g., n. sp. (Digenea: Cryptogonimidae) from the eastern water snake Sinonatrix percarinata (Boulenger) (Serpentes: Colubridae) in Guizhou Province, China.

Serpentoanisocladium sinense n. g., n. sp. (Digenea: Cryptogonimidae) is described from the intestine of the eastern water snake Sinonatrix percarinata (Boulenger) (Serpentes: Colubridae) from Guizhou Province, China. This digenean is morphologically most similar to members of Anisocladium Looss, 1902 and, to a lesser extent, Anisocoelium Lühe, 1900, which are parasites of marine teleost fish in the Mediterranean and Black Seas. The new genus and species can be differentiated from the two known species of Anisocladium by the position of the vitellarium in relation to the gonads and seminal vesicle, a much longer oesophagus, a shorter caecum only reaching the anterior margin of the anterior testis, the presence of a muscular sucker-like gonotyl, the lack of circumoral spines and the peculiar position of the uterus, which is confined to the same half of the body as the longer caecum. The new genus and species can be differentiated from the only known species of Anisocoelium by the substantially higher body length to width ratio, a much longer oesophagus, the arrangement of the vitelline follicles, the postovarian versus pre-ovarian seminal receptacle, the presence of a well-defined muscular gonotyl and the length of the shorter caecum. A diagnosis of the new genus and a description of the new species are provided. This is the first cryptogonimid found in snakes from China and the first cryptogonimid reported from S. percarinata.