The microsnail genera Clostophis and Acinolaemus (Eupulmonata, Pupilloidea, Hypselostomatidae) from central Thailand, with description of three new species

Hypselostomatid microsnails of the genera Clostophis and Acinolaemus from limestone hills in central Thailand were studied and three new species are described. Clostophis rhynchotes Tongkerd & Panha, sp. nov. is diagnosed by a conical spire, long and descending tuba, 14 spiral striations on the last whorl, and only a single parietal lamella. In addition, a previously known species, C. proboscideus, is redescribed, and variations in its apertural dentition are also documented.

In the genus Acinolaemus, two new sympatric species that clearly differ in shell shape are described. Acinolaemus rhamphodontis Tongkerd & Panha, sp. nov. is characterised by a depressed conical spire with a long and descending tuba, and eight apertural dentitions, while A. corusticorus Tongkerd & Panha, sp. nov. possesses a conical shell without a tuba and nine apertural dentitions. Specimens from the type locality of A. ptychochilus (the type species), A. cryptidentatus and A. mueangonensis are re-described and compared with the new species.

The living snails of A. mueangonensis and A. rhamphodontis Tongkerd & Panha, sp. nov. possess blackish to translucent bodies. In addition, COI barcoding data for Clostophis and Acinolaemus are provided for the first time.