Gyliotrachela aunglini Tongkerd & Panha, 2024

Tongkerd, Piyoros, Lwin, Ngwe, Pall-Gergely, Barna, Chanabun, Ratmanee, Pholyotha, Arthit, Prasankok, Pongpun, Seesamut, Teerapong, Siriwut, Warut, Srisonchai, Ruttapon, Sutcharit, Chirasak & Panha, Somsak, 2024, Contributions of a small collection of terrestrial microsnails (Pupilloidea, Hypselostomatidae) from Myanmar with description of three new species, ZooKeys 1195, pp. 157-197 : 157

Gyliotrachela aunglini Tongkerd & Panha sp. nov.

Figs 12 , 13P

Type locality.

Kaw Gon Cave, Hpa-An, Kayin State, Myanmar (locality code PA5; 16°49'22.2"N, 97°35'08.9"E).

Type material.

Holotype CUMZ 14383 (height 1.8 mm, width 1.6 mm; Fig. 12A, B ). Paratypes CUMZ 14384 (2 shells); CUMZ 14411 (16 shells; measured); CUMZ 14412 (2 shell; Figs 12C, D , 13P ), NHMUK 20230593 (2 shells), SMF 373021 (2 shells) all from the type locality.

Diagnosis.

Shell ovate-conical with shouldered and flat-sided last whorl, aperture not detached from penultimate whorl; shell surface irregularly wrinkled, colour pale reddish brown; aperture roundly triangular, with five or six apertural dentitions (angular, parietal, upper palatal, lower palatal and columellar).

Etymology.

The specific name aunglini is named after Mr. Aung Lin, the FFI coordinator, who took care of the survey team and arranged the limestone survey trip in Myanmar between 2015 and 2016.

Description.

Shell broadly ovate-conical, pale reddish brown in colour, moderate spire, and 4½ -5 widely convex whorls. Shell height 1.6-1.8 mm and shell width 1.6-1.8 mm. Apex blunt; protoconch with 1¾ whorls, wrinkled, with roundish pits and weak spiral ridges. Teleoconch with narrowly spaced radial growth lines, parallel with very strong, irregular wrinkles; suture well impressed. Last whorl bluntly shouldered and flat-sided with shallow groove below shoulder. Tuba absent; peristome adnate and widely expanded; lip whitish to yellowish. Aperture roundly triangular and with five dentitions. Parietal lamella large, strong, blunt and located somewhat deeper inside aperture than angular lamella. Angular lamella strong and reaching peristome. Upper palatal plica strong, tall and approximately same size as parietal lamella; lower palatal plica strong and lower than upper palatal plica. Columellar lamella strong, distinct and pointing slightly upwards. Umbilicus widely perforate, ~ 1/3 of shell width, rounded, shallow, and surrounded by curved periumbilical keel.

Distribution.

This new species is currently known only from the type locality in Kayin State. This snail lives on the limestone walls and under leaf litter.

Differential diagnosis.

Gyliotrachela aunglini sp. nov. differs from G. bensonianum and G. tianxingqiaoensis from Myanmar in having high spire, peristome adnate to preceding whorl, shouldered last whorl, with very weak spiral striae on protoconch, and only five apertural dentitions (parietal, angular, upper- and lower- palatal, and columellar). In contrast, the other two species possess a depressed spire, a short and slightly ascending tuba, and an angular last whorl. Additionally, G. bensonianum has a spirally striated teleoconch, and it has a basal plica and infraparietal lamella; G. tianxingqiaoensis possesses numerous small accessory plicae and lamellae ( Gojšina et al. 2022).

This new species can be distinguished from G. saraburiensis , G. muangon , and G. cultura (all known from Thailand) by having no tuba (i.e., peristome adnate to preceding whorl), possessing a shouldered last whorl, strong wrinkles on the shell surface and bearing only five to six major dentitions. In contrast, the three species from Thailand tend to have a short and slightly ascending tuba, an angular to weakly angular last whorl, spiral striae on the teleoconch, and numerous accessory plicae and lamellae inside the aperture ( Burch et al. 2003; Panha et al. 2004; Panha and Burch 2005; Tanmuangpak and Dumrongrojwattana 2022).

Several Gyliotrachela species from southern Thailand are similar to the new species by having very short tuba, and few apertural dentitions. Gyliotrachela aunglini sp. nov. differs from G. transitans (von Möllendorff, 1894) in the short and slightly descending tuba, the angular last whorl, and the apertural dentition with supracolumellar lamella and a basal plica; G. tarutao (Panha & Burch, 2002) has an elevated spire, an angular last whorl, a very short tuba, and the apertural dentition is characterised by a subcolumellar lamella, an infraparietal plica and a basal plica ( von Möllendorff 1894; Panha and Burch 2002b, 2005). The new species differs from G. adela Thompson & Upatham, 1997 in the depressed spire, the short and descending tuba, with prominent spiral striae on the teleoconch, and apertural dentition with a basal plica ( Thompson and Upatham 1997).

Further comparison can be made with species from Peninsular Malaysia that have a very short tuba and few apertural dentitions. Gyliotrachela aunglini sp. nov. differs from G. emergens van Benthem Jutting, 1950 and G. modesta van Benthem Jutting, 1950 in having an elevated spire, short and slightly descending tuba and an angular or weakly angular last whorl. In addition, the apertural dentition of the former species includes a basal plica, and supra- and sub- columellar lamellae, while the latter species has a supracolumellar lamella and a weak infrapalatal plica. Additionally, this new species differs from G. troglodytes van Benthem Jutting, 1950 in the depressed spire, the very short and descending tuba, the angular last whorl, the apertural dentition with infraparietal and weak angular lamellae, and the strongly wrinkled shell surface ( van Benthem Jutting 1950).

Remarks.

The material examined here shows minor variability in terms of shell size, but the key morphological characters, shell sculpture and apertural dentition, are reliable.

Figures

Figure 12. Gyliotrachela aunglini sp. nov. from Hpa-An, Kayin State A, B holotype CUMZ 14383, (A) shell and (B) protoconch C, D paratypes CUMZ 14412 from the type locality. Abbreviations: a: angular lamella, c: columellar lamella, lpl: lower palatal plica, p: parietal lamella, upl: upper palatal plica.

Figure 13. Synoptic view of representatives of hypselostomatid snails recorded from Myanmar A Acinolaemus dayanum, specimen HA Collection B Acinolaemus cryptidentatus, specimen CUMZ 14413 C Anauchen eotvosi, holotype NHMUK 1903.7.1.1227.1 (after Pall-Gergely 2023 a: fig. 1 c) D Angustopila occidentalis, holotype HNHM 103483 (after Pall-Gergely et al. 2023: fig. 70 a) E Angustopila elevata, specimen HNHM 103484 (after Pall-Gergely et al. 2023: fig. 13 a) F Bensonella salwiniana, specimen CUMZ 14393 G Bensonella anguloobtusa, specimen CUMZ 14400 H Bensonella taiyaiorum sp. nov., paratype CUMZ 14403 I Bensonella lophiodera sp. nov., paratype CUMZ 14405 J Clostophis sankeyi, holotype UMZC I. 103320 (after Preece et al. 2022: fig. 70 e) K Clostophis thinbowguensis, holotype MNHN-IM- 2000 - 38057 (after Pall-Gergely et al. 2022: fig. 9 c) L Gyliotrachela bensonianum, syntype NHMUK 20191141 (after Gojsina et al. 2022: fig. 4 a) M Gyliotrachela hungerfordiana, specimen NHMUK collection from Perak, Malaysia N Gyliotrachela tianxingqiaoensis, holotype IZCAS TM 025075 (after Gojsina et al. 2022: fig. 3 a) O Gyliotrachela muangon, specimen CUMZ 14410 P Gyliotrachela aunglini sp. nov., paratype CUMZ 14412 Q Hypselostoma tubiferum, specimen NHMUK 1888.12.4.17 - 22 ex. Theobald collection from Tonduong, Burma.