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| A, B. Hypselostoma pongrati sp. nov. C, D. Hypselostoma sichomphuense sp. nov. Tanmuangpak & S. Tumpeesuwan, in Tanmuangpak, Nahok, Chanlabut, C. Tumpeesuwan et S. Tumpeesuwan, 2025. |
Abstract
Two new species of hypselostomatid land microsnails, Hypselostoma pongrati Tanmuangpak & S. Tumpeesuwan, sp. nov. from Nong Bua Lamphu Province and H. sichomphuense Tanmuangpak & S. Tumpeesuwan, sp. nov. from Khon Kaen Province, are described based on the morphology of their shell, radula, and genital system. Both new species are very similar in shell shape to H. phupaman from Chaiyaphum Province, possessing a double-keeled last whorl. However, H. pongrati Tanmuangpak & S. Tumpeesuwan, sp. nov. is distinguished by the absence of apertural barriers, whereas H. sichomphuense Tanmuangpak & S. Tumpeesuwan, sp. nov. possesses three apertural barriers, and H. phupaman possesses six or seven. The three species were found on isolated limestone hills in the Chaiyaphum-Khon Kaen-Nong Bua Lamphu-Loei area.
Key words: Apertural barriers, double-keeled last whorl, genital system, limestone hills, radula
Taxonomy
Family Hypselostomatidae Zilch, 1959
Genus Hypselostoma W.H. Benson, 1856
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| Living Hypselostoma spp. A, B. Hypselostoma pongrati sp. nov. paratype NHLRU015; C, D. H. sichomphuense sp. nov. paratype NHLRU033. |
Hypselostoma pongrati Tanmuangpak & S. Tumpeesuwan, sp. nov.
Diagnosis. This new species has a prominent keel on the upper part of the last whorl and a weaker keel on the lower part. Apertural barriers absent (Fig. 3A, G, H, L). Terminal part of the last whorl is adnated to penultimate whorl.
Etymology. This new species is dedicated to the late Pongrat Dumrongrojwattana, our highly respected senior who was an expert on microsnails and who provided us with many land snails references, knowledge, and inspiration.
Hypselostoma sichomphuense Tanmuangpak & S. Tumpeesuwan, sp. nov.
Diagnosis. This new species differs from Hypselostoma phupaman by the presence of a non-prominent lower keel on the last whorl and the absence of basal and parietal apertural barriers. Aperture has three smooth tooth-like swellings (Fig. 4A, G–I), whereas there are no apertural barriers in H. pongrati sp. nov. (Fig. 3A, G–I). Spire shorter than the spire of H. pongrati sp. nov.
Etymology. The specific epithet sichomphuense refers to Si Chomphu District, Khon Kaen Province, northeastern Thailand, where this species was discovered.
Kitti Tanmuangpak, Benchawan Nahok, Utain Chanlabut, Chanidaporn Tumpeesuwan and Sakboworn Tumpeesuwan. 2025. Two New Species of terrestrial Microsnails of the genus Hypselostoma W.H. Benson, 1856 (Gastropoda, Eupulmonata, Hypselostomatidae) from northeastern Thailand. ZooKeys. 1265: 49-67. DOI: doi.org/10.3897/zookeys.1265.160661
