Bensonella taiyaiorum 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

Bensonella taiyaiorum Tongkerd & Panha sp. nov.

Figs 7B , 8 , 13H

Type locality.

Dragon Rock, Pindaya Township, Taunggyi District, Shan State, Myanmar (locality code SH6; 20°55'31.5"N, 96°39'01.2"E; 1300 m a.s.l.).

Type material.

Holotype CUMZ 14380 (height 2.8 mm, width 2.1 mm; Fig. 7B ). Paratypes CUMZ 14381 (41 shells); CUMZ 14402 (12 shells; measured); CUMZ 14403 (3 shells; Figs 8 , 13H ), NHMUK 20230591 (3 shells), SMF 373019 (3 shells) all from the type locality.

Diagnosis.

Shell elongate-conical and yellowish brown in colour. Cervical crest situated far from peristome. Aperture with several hookless barriers (i.e., parietal, infraparietal, angular, columellar, supra- and sub-columellae, basal, and upper, inter and lower palatals), and interpalatal and lower palatal plicae forming u-shaped plica.

Etymology.

The specific name taiyaiorum is in recognition of the 'Tai Yai’ or ‘Shan’, the largest ethnic group in Shan State, which is the type locality of this species.

Description.

Shell conical, yellowish brown to reddish brown and with 5¼ -6 widely convex whorls. Shell height 2.5-2.9 mm and shell width 2.0-2.2 mm. Apex blunt; protoconch ~ 1½ whorls with wrinkles and very weak spiral ridges. Teleoconch with strong and irregular growth lines, sometimes white growth lines are conspicuous; suture impressed and deep. Last whorl large and rounded. Peristome thickened and slightly expanded; constriction weak; lip reddish brown. Cervical crest sharp and situated far from peristome. Aperture subrectangular and with many apertural dentitions. Parietal lamella strongly developed and consisting of two parts separated by an incision: outer part large, strong, with rectangular shape and reaching peristome; inner part blunt. Infraparietal lamella small and blunt. Angular lamella lower than parietal lamella: outer part short and reaching peristome; inner part more strongly elevated. Palatal tubercle strongly developed with triangular shape; two upper palatal plicae with strong folding; inter- and lower palatal large, equal in size and connected to form u-shaped plica. Basal plica small, low and tubercle-like. Columellar lamella large, strong and distinct in its horizontal alignment; one small supracolumellar lamella and one small subcolumellar lamella present. Umbilicus narrowly perforate, ~ 1/5 of shell width, rounded and deep.

Distribution.

This new species is known only from the type locality in Shan State. The snails live on limestone walls and can be found under leaf litter within rock crevices.

Differential diagnosis.

The new species can be distinguished from Bensonella reported from Thailand and Laos in having inter- and lower- palatal plicae connected, forming a u-shaped plica, and with prominent cervical crest. In contrast, the three species from Thailand differ by: B. nabhitabhatai has one upper palatal plica and no supracolumellar and infraparietal lamellae; B. tamphathai possesses fine spiral striae on the teleoconch, one upper palatal plica, and bears no supracolumellar lamellae; B. pangmapaensis has fine spiral striae on the teleoconch, and hooked palatal and basal plicae ( Panha and Burch 2000, 2002b, 2005; Panha et al. 2003; Inkhavilay et al. 2016).

For further comparison, the three species from Laos can be distinguished by: B. paralella has one upper palatal plica, and no interpalatal plicae, supra- and sub- columellar lamellae; B. anguloobtusa has one upper palatal plica and no basal and supracolumellar lamellae; B. wangviangensis has a unique shape, smaller shell size (height 1-2 mm), four whorls, shouldered last whorl, and bears no basal plicae and columellar lamellae ( Panha et al. 2003; Inkhavilay et al. 2016).

Remarks.

The two new species, B. taiyaiorum sp. nov. and B. lophiodera sp. nov., are the first Bensonella species to be described from Myanmar. The strongly developed and separated parietal and angular lamellae, and lack of a tuba are the main characters underscoring the assignment of these species to Bensonella .

Though the spiral striae on the protoconch are obscured under the light microscope, they are very faint but detectable under the SEM microscope. Of all the type series examined, no hooked-shaped dentitions were observed, while the u-shaped plicae are present in all specimens. A constriction on the palatal wall near the aperture and the cervical crest is possibly an important trait in response to resistance to desiccation.

Figures

Figure 7. A Bensonella anguloobtusa, specimen CUMZ 14398 from Taunggyi District, Shan State B Bensonella taiyaiorum sp. nov., holotype CUMZ 14380 from Taunggyi District, Shan State C Bensonella lophiodera sp. nov., holotype CUMZ 14378 from Taunggyi District, Shan State. Abbreviation: ip: infraparietal lamella.

Figure 8. Bensonella taiyaiorum sp. nov., from Taunggyi District, Shan State A-C paratypes CUMZ 14403. The white arrow indicates constriction. The yellow arrow indicates a cervical crest. Abbreviations: a: angular lamella, b: basal plica, c: columellar lamella, ip: infraparietal lamella, itpl: interpalatal plica, lpl: lower palatal plica, p: parietal lamella, pt: palatal tubercle, sbc: subcolumellar lamella, spc: supracolumellar lamella, sppl: suprapalatal 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.