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.

Annotated checklist of the operculated land snails from Thailand (Mollusca, Gastropoda, Caenogastropoda): the family Pupinidae, with descriptions of several new species and subspecies, and notes on classification of Pupina Vignard, 1829 and Pupinella Gray, 1850 from mainland Southeast Asia

“…More recently, land snail research in Thailand was boosted after SP began studying Thai land malacofauna in the 1990s (Panha 1996). A number of operculated land snails from the families Alycaeidae, Cyclophoridae and Diplommatinidae were described (Panha andBurch 1998, 2005;Panha and Patamakanthin 2001;Nantarat et al 2014Nantarat et al , 2019Sutcharit et al 2014;Jirapatrasilp et al 2021). However, most malacological studies focused on pulmonate land snails, e.g., the families Ariophantidae (Pholyotha et al 2020;Sutcharit and Panha 2021), Camaenidae (Sutcharit and Panha 2006), Gastrocoptidae (Panha and Burch 2005), and Streptaxidae (Siriboon et al 2014a, b).…”

Two new species of Dicharax Kobelt & Möllendorff, 1900 from Myanmar and one from Thailand (Gastropoda: Caenogastropoda: Alycaeidae)

“…Measurements: SW 5 5.01 mm, SH 5 3.06 mm. D. cucullatus is similar to this new species in size and the long R2, but its R3 swelling is situated closer to the peristome, lacks a second R2 swelling, and has a fringed aperture (see Jirapatrasilp et al, 2021). Dicharax woodthorpei (Godwin-Austen, 1914) (see Páll-Gergely et al, 2021) is also somewhat similar to the new species in terms of general shell and aperture shape, but it lacks a conspicuous second R3 swelling, and its R2 bears no elevated ribs, but has light and dark alternating colour stripes (or some of the R2 ribs may be separated individually at the beginning of R2).…”

“…However, D. blanfordi is much larger, the inner peristome is less fringed, and the outer peristome is less expanded. Dicharax cucullatus (Theobald, 1870) is larger, it has a more depressed spire, a shorter R3 with a narrower swelling, a much less prominent outer peristome, and denser R1 and R2 ribs, and the same is true for D. davisi (Godwin-Austen, 1914) (see Jirapatrasilp et al, 2021) and D. ochraceus (Godwin-Austen, 1893) (material examined: Ruby mine Disr., Up. Burma, leg.…”

“…One of the hotspots of Dicharax is found in the southeastern Himalaya, and this remarkable diversity continues in Myanmar and northern Thailand (Páll-Gergely et al, 2021). Namely, 23 Dicharax species are known in Myanmar, and 14 from Thailand (Páll-Gergely and Auffenberg, 2019;Jirapatrasilp et al, 2021). In the following, we describe two new Dicharax species from Myanmar's Shan State, and one from the Erawan National Park in Thailand.…”

“…Its geographic range spans between India (western Himalaya, see Sajan et al, 2020 and Western Ghats, see Aravind and Páll-Gergely, 2018) in the west, the Japanese Honshu Island in the east, and southern Indonesia in the south (Godwin-Austen, 1882-1920Gude, 1921;van Benthem Jutting, 1948, 1959Minato, 1988;Gittenberger et al, 2017;Páll-Gergely and Auffenberg, 2019). The family currently has 344 extant species (Páll-Gergely and Auffenberg, 2019;Páll-Gergely et al, 2021;Jirapatrasilp et al, 2021;MolluscaBase eds., 2022). The most specious genus is Dicharax Kobelt and Möllendorff, 1900, which currently contains 158 species (MolluscaBase eds., 2022).…”