A review of the land snail genus Alycaeus (Gastropoda, Alycaeidae) in Peninsular Malaysia

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

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.

Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue

412 species-group names (including 11 replacement names), and 14 genus-group names of the Alycaeidae have been introduced to date. Type materials of 85% (336) of the known species and subspecies were examined, a further 5% (19) of the taxa were studied using available non-type material, and for another 6% (22) the original descriptions were sufficiently detailed to evaluate their taxonomic status. Only 3% of the taxa (12) could not be examined. Special attention was paid to the sculpture of the embryonic whorls and the sutural tube-microtunnel system in order to provide a novel classification for this group.

In this study 363 taxa (320 species or 43 subspecies) are accepted within the family Alycaeidae. Of these, 22 have been described by the lead author and his coauthors in previous publications. In addition, there are 18 species that were formerly classified in Cycloryx and now belong to Pincerna due to its synonymy with Cycloryx. Among the remaining 323 species, 209 (65%) are transferred here to another genus, whilst 114 (35%) have remained in their original genus.

Seven genera are accepted. While some questions (e.g., the distinction between Pincerna and Alycaeus) remained unanswered, this revision made three main achievements: (1) The Dicharax species were identified based on the absence of spiral striation on the entire shell; (2) the Metalycaeus species were identified based on the spiral striation of the protoconch; (3) and Stomacosmethis was separated from Alycaeus based on the extremely short sutural tube.

Five nominal species are being synonymised with other species, and eight species are now treated as subspecies. The following replacement names are proposed: Dioryxurnulaniosiensis Páll-Gergely, nom. nov. for Alycaeusurnulavar.daflaensis Godwin-Austen, 1914; Dioryxurnularotundus Páll-Gergely, nom. nov. for Alycaeusurnulavar.globosus Godwin-Austen, 1914; Pincernacrenilabrisjuttingae Páll-Gergely, nom. nov. for Alycaeuscrenilabrislaevis van Benthem Jutting, 1959; Pincernacrenilabriskorintjiensis Páll-Gergely, nom. nov. for Alycaeuscrenilabrislatecostatus van Benthem Jutting, 1959; Dicharaxconicusjatingaensis Páll-Gergely, nom. nov. for Alycaeusconicusvar.nanus Godwin-Austen, 1914; Metalycaeusgodwinausteni Páll-Gergely, nom. nov. for Alycaeusneglectus Godwin-Austen, 1914; and finally Metalycaeussuhajdai Páll-Gergely, nom. nov. for Alycaeusvarius Godwin-Austen, 1914.