Haploptychius thebawi (Godwin-Austin, 1888)

Sian Man, Nem, Siriboon, Thanit, Lin, Aung, Sutcharit, Chirasak & Panha, Somsak, 2022, Revision of the carnivorous land snail family Streptaxidae (Stylommatophora, Achatinina) in Myanmar, with description of four new species, ZooKeys 1110, pp. 39-102 : 39

Haploptychius thebawi (Godwin-Austin, 1888)

Figs 1 , 12

Streptaxis thebawi Godwin-Austin, 1888: 243. Type locality: Pingoung, Shan Hills [Pinlaung Township, Taunggyi District, Shan State, Myanmar]. Gude 1903: 212, 322, 325, pl. 12, figs 11-13.

Haploptychius thebawi - Kobelt 1906: 145, 146: pl. 62, figs 11-13. Richardson 1988: 222.

Material examined.

Limestone hills (Apache Cement Factory), Pyinyaung Village , Thazi Township , Meiktila District , Mandalay Region, Myanmar (20°49'39.1"N, 96°23'35.1"E): CUMZ 13008 (4 shells; Fig. 12A-C ). Ywangan Village , near Lin Way Monastery, Kalaw Township , Taunggyi District , Shan State, Myanmar (21°13'43.3"N, 96°33'19.2"E): CUMZ 13009 (7 shells). Aik Kham Cave , Taunggyi Township, Taunggyi District, Shan State, Myanmar (20°49'07.0"N, 97°13'42.0"E): CUMZ 13010 (3 shells; Fig. 12D, E ) .

Diagnosis.

Haploptychius thebawi is similar to H. solidulus in having a high conical spire and globosely ovate shell. The former species can be discriminated by its smoother shell surface and narrower aperture, more rounded and extended penultimate whorl, and less inflated last whorl. Additionally, H. thebawi resembles H. porrectus (Pfeiffer, 1863) from Laos in having strong radial ridges, conical spire, and an inflated and deflected last whorl, whereas H. thebawi exhibits a larger shell, less depressed and deflected last whorl, fine radial ridges, and higher spire.

Description.

Shell oblique-heliciform, white and translucent; whorls 5½-6½; spire conical with distinct suture. Shell surface glossy with transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture subcircular; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 12 ).

Distribution.

This species occurs in central-eastern Myanmar, based on the type locality and two localities in Shan State, one locality in Mandalay Region, and it is relatively low in population density.

Remarks.

Originally, H. thebawi was described based on specimens from Pingoung, Shan Hills, which is probably now referred to as Pinlaung Township, Taunggyi District, Shan State. Unfortunately, the type specimens of H. thebawi could not be located in the NHM, London collection. However, the specimens examined herein match well with the original description and the syntype illustrated in Gude (1903: figs 11-13). Despite that, the specimens from Mandalay Region tend to have a more ovate shell and elongated last whorl, and their smooth shell surface, narrow umbilicus, and conical spire make them most similar to this nominal species. Therefore, we treat this population as an intraspecific variation. Examination of genitalia of specimens from this population is necessary to clarify their taxonomic status.

Blanford and Godwin-Austen (1908) treated this nominal species as a junior synonym of H. burmanicus . However, the recently collected specimens of H. thebawi can be distinguished from H. burmanicus and H. blanfordi by having an oblique-ovate to oblique-heliciform shell, elevated and conical spire, nearly smooth shell surface, penultimate whorl extended beyond last whorl, only one parietal lamella, and narrow umbilicus. Conversely, the two latter species have sub-oblique heliciform shells, depressed spire, prominent radial ridges on the shell surface, penultimate whorl slightly extended beyond the last whorl, with one parietal and one palatal lamella, and a wide umbilicus. Therefore, we consider H. thebawi to stand as a separate species.

Among three populations of H. thebawi (Table 1 ), Aik Kham Cave specimens have the smallest size with a more depressed shell, followed by Ywangan Village; Apache Cement Factory specimens have the largest shell with more conical spire and rounded last whorl.

Figures

Figure 1. Approximate sampling locations used in this study. The location name and coordinates are listed in Table 1. Historical type localities of a broad scale, such as Tavoy, Burma, Moulmein, Mergui, and Tenasserim, are not indicated on this map.

Figure 12. Haploptychius thebawi A-C specimens CUMZ 13008 from Pyinyaung Village, Meiktila, Mandalay Region, with apertural dentition D, E specimens CUMZ 13010 from Aik Kham Cave, Taunggyi, Shan State.