Bensonella lophiodera 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 lophiodera Tongkerd & Panha sp. nov.

Figs 7C , 9 , 13I

Type locality.

Myinmati Cave, Kalaw Township, Taunggyi District, Shan State, Myanmar (locality code SH4; 20°35'24.6"N, 96°36'42.1"E; 1312 m a.s.l.).

Type material.

Holotype CUMZ 14378 (height 3.1 mm, width 1.8 mm; Fig. 7C ). Paratypes CUMZ 14379 (16 shells); CUMZ 14404 (12 shells; measured); CUMZ 14405 (3 shells; Figs 9 , 13I ), NHMUK 20230592 (3 shells), SMF 373020 (3 shells) all from the type locality.

Diagnosis.

Shell ovate-conical, high spired and pale yellowish brown colour. Cervical crest situated far from peristome. Lip not expanded. Aperture usually with seven barriers (parietal, infraparietal, angular, columellar, basal, and upper and lower palatals). Palatal tubercle is lacking.

Etymology.

The specific name lophiodera is a compound of the Greek words lophia meaning crest and dere meaning neck or throat. It refers to the prominent cervical crest on the palatal wall of the last whorl.

Description.

Shell ovate-conical, pale yellowish brown in colour, high spire and 5½ -6 convex whorls. Shell height 2.7-3.2 mm and shell width 1.9-2.1 mm. Apex blunt; protoconch consisting of ~ 1½ whorls with wrinkles and weak spiral ridges. Teleoconch with somewhat strong and irregular growth lines; suture well impressed and deep. Last whorl large and rounded. Peristome slightly thickened and little expanded; constriction very weak; lip yellowish brown. Cervical crest sharp and situated close to peristome. Aperture subrectangular with seven or eight apertural barriers. Parietal lamella large, strongly developed, blunt, u-shaped from side view; infraparietal lamella small and knob shaped. Angular lamella weaker than parietal: outer part very low, weak and reaching peristome; inner part strong and tall. Palatal tubercle inconspicuous. Upper palatal plica small and low; lower palatal plica strong and tall, blunt. Basal plica small tubercle-like. Columellar lamella large and strong; sometimes an additional tiny subcolumellar lamella is present. Umbilicus narrowly perforate, ~ 1/5 of shell width, rounded and deep.

Distribution.

This species is currently known only from the type locality in Shan State. The living snails are found on limestone walls and under leaf litter in rock crevices.

Differential diagnosis.

This new species is similar to B. salwiniana in shell shape, number of apertural dentitions, and bears no palatal tubercle. However, B. lophiodera sp. nov. differs by having a strong cervical crest, and a very thin, fragile and unexpanded lip, while B. salwiniana shows no cervical crest, and has a thickened and expanded lip.

The new species is distinguishable from Bensonella reported from Thailand and Laos in having a weak palatal tubercle, a cervical crest, slightly expanded lip, no interpalatal plica, and apertural barriers are generally weak. Regarding the three species from Thailand, B. nabhitabhatai has one upper palatal plica, and lacks the basal plica and the infraparietal lamella; B. tamphathai possesses two interpalatal plicae, and its shell is sculptured with spiral striae; B. pangmapaensis has fine spiral striae and hooked palatal and basal plicae ( Panha and Burch 2000, 2002b, 2005; Panha et al. 2003; Inkhavilay et al. 2016).

There are three Bensonella species known from Laos. Among them, B. paralella has an expanded lip and strongly prominent apertural dentitions; B. anguloobtusa has strong and sinuous apertural dentitions, and is sculptured with weak spiral striae; B. wangviangensis has a unique shell shape with small shell size (height 1-2 mm), a nearly closed sinulus, a shouldered last whorl, and lacks a basal plica and columellar lamella ( Panha and Burch 2000, 2002b, 2005; Panha et al. 2003; Inkhavilay et al. 2016).

In addition, B. lophiodera sp. nov. differs from B. taiyaiorum sp. nov. in having eight apertural barriers, an inconspicuous palatal tubercle, one upper palatal plica, and lacking a supracolumellar lamella and interpalatal plica. In contrast, B. taiyaiorum sp. nov. possesses an expanded lip, has a strong palatal tubercle, two upper palatal plicae, and the inter- and lower- palatal plicae are connected and form a U-shaped plica.

Remarks.

The spiral striae on the protoconch are very faintly detectable under the SEM microscope. Among all the type series examined, no hooked-shaped dentitions were observed, while the apertural dentitions show minor variability in different degrees of thickness and sharpness. A clear constriction at the palatal wall near the aperture and a sharp cervical crest are present in all specimens.

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 9. Bensonella lophiodera sp. nov., from Taunggyi District, Shan State A-C paratypes CUMZ 14405. 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, lpl: lower palatal plica, p: parietal lamella, sbc: subcolumellar 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.