The operculate micro land snail genus Dicharax Kobelt & Möllendorff, 1900 (Caenogastropoda, Alycaeidae) in Thailand, with description of new species

Abstract

This study reviews the Dicharax species in Thailand. Altogether ten Dicharax species are reported, four of which are new to science and described herein. They are Dicharax borealis Jirapatrasilp & Páll-Gergely sp. nov., Dicharax burchi Jirapatrasilp & Páll-Gergely sp. nov., Dicharax panhai Jirapatrasilp & Páll-Gergely sp. nov. and Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov.Alycaeus davisi Godwin-Austen, 1914 is regarded as a junior subjective synonym of Alycaeus cucullatus Theobald, 1870 (= D. cucullatus) based on a similar depressed-conical shell shape, a long sutural tube and a sharp swelling behind the peristome. Furthermore, the type locality of Alycaeus pratatensis Panha & Burch, 1997 (= D. pratatensis) had to be amended. Most important characters to distinguish Dicharax species are the general shell shape and relative lengths of teleoconch regions, whereas the spiral striation of R1, the shape of swelling of R3, the outer peristome crenulation and protrusion, and the exterior opercular sculpture show large intraspecific variability.