Bensonella salwiniana (Theobald, 1871)

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 salwiniana (Theobald, 1871)

Figs 4 , 5 , 6A , 13F

Hypselostoma Pupa salwiniana Theobald, 1871: 400. Type locality: Shan States. Hanley and Theobald 1874: 40, pl. 100, fig. 9. Sowerby 1877: Pupa pl. 16, fig. 150. Pfeiffer 1877: 403.

Hypselostoma Pupa (Scopelophila) salwiniana. Nevill 1877: 23.

Hypselostoma Pupa (Pupilla) salwiniana. Pfeiffer 1880: 355.

Hypselostoma Pupa salwinieana [sic]. Godwin-Austen 1888: 244.

Boysidia salwiniana . Gude 1914: 295, 296. Pilsbry 1917: 206-208, pl. 33, fig. 11.

Material examined.

Burma [ Myanmar]: NHMUK 1912.4.16.66 (2 shells; Fig. 4A ) ex. Beddome collection. Shan State : SMF 227428/2 (2 shells). Monastery, Ywangan Township, Taunggyi District , Shan State , Myanmar (locality code SH1; 21°13'43.3"N, 96°33'19.2"E): CUMZ 14375 (1 shell; Fig. 4E ); CUMZ 14391 (2 shells); CUMZ 14392 (11 shells; measured); CUMZ 14393 (2 shells; Figs 4F , 6A , 13F ). Dragon Rock , Pindaya Township , Taunggyi District , Shan State , Myanmar (locality code SH5; 20°55'31.5"N, 96°39'01.2"E): CUMZ 14376 (1 shell; Fig. 4D ); CUMZ 14394 (4 shells). Blue Diamond Co., Ltd. , Pyigyidagun Township , Mandalay Region , Myanmar (locality code MD1; 21°54'12.4"N, 96°04'38.8"E): CUMZ 14377 (1 shell; Fig. 4B, C ); CUMZ 14395 (1 shell). Aik Kham Cave, Taunggyi District , Shan State , Myanmar (locality code SH10; 20°49'07.0"N, 97°13'42.0"E): CUMZ 14396 (22 shells). Montawa Cave, Taunggyi District , Shan State , Myanmar (locality code SH11; 20°45'15.8"N, 97°01'03.1"E): CUMZ 14397 (85 specimens in ethanol; Fig. 5 ) .

Description.

Shell ovate-conical, high spire, yellowish brown, with 6- 6½ convex whorls. Shell height 5.6-6.3 mm and shell width 3.3-3.7 mm. Apex blunt; protoconch ~ 1½ whorls, sculptured with radial wrinkles. Teleoconch with smooth, irregular growth lines; suture well impressed and deep. Last whorl large and rounded. Peristome thickened and broadly expanded; lip whitish. Aperture rounded-subquadrate with six or seven dentitions. Parietal lamella large, long, strong, broadly blunt, and located slightly deeper inside aperture; infraparietal lamella very small and sometimes absent. Angular lamella blunt and reaching peristomal lip. Palatal tubercle inconspicuous. Upper palatal plica long, contacting peristome and sometimes elevated in middle; lower palatal plica strong and large. Basal plica weak to strong nodule shape. Columellar lamella strong and large, tubercle-like. Umbilicus very narrowly perforate, rounded and deep.

Genital system. Atrium short and slightly enlarged. Penis very long, thin tube and slightly enlarged at both ends; penial appendix short. Penial retractor muscle large and inserted between penis and epiphallus junction. Epiphallus slender tube, almost same length as penis, and ~ 2/3 of its length enlarged with similar diameter to free oviduct. Vas deferens very thin tube, connected between epiphallus and free oviduct, and held in position with thin connective tissue near epiphallus-vas deferens junction to atrium.

Vagina slender tube, short and ~ 1/3 of penis length. Gametolytic organ strongly developed; gametolytic duct slender tube, almost same length as vagina+free oviduct; gametolytic sac enlarged and bulbous. Free oviduct larger in diameter than vagina, and approximately same length as vagina.

Animal. Preserved specimen with blackish to greyish reticulated skin, and mantle collar well-developed and whitish. Pneumostome wide and situated in the bay of angular lamella and upper palatal plicae. Foot short, holopodal, unipartite, and sole of foot blackish to greyish in colour. Living snails possess blackish tentacles: upper tentacles short and stout, and lower tentacles very short.

Radula . Teeth arranged in nearly straight row with formula 15-(6, 5)-1-(5, 6)-11+. Central tooth unicuspid, with long triangular shape and pointed tip. Lateral teeth bicuspid, inner and outer cusps clearly separated at base, situated next to each other, and nearly aligned in transverse row. Inner and outer cusps long and triangular, and outer cusp comparatively smaller than inner cusp. Marginal teeth starting at approximately tooth number 5 or 6, inner and outer cusps of marginals joined at base. Innermost marginals bicuspid, similar to lateral teeth; outermost teeth multicuspid, cusps small with almost same size and shape, and situated on same base.

Distribution.

This species is known from several localities in northern Myanmar: Bhamo [Bhamo District, Kachin State]; Pingoung [Pingku Hills, Muse District, Shan State]; Shan Hills ( Gude 1914; Pilsbry 1917). In this study, several specimens were also collected from Shan State and the Mandalay Region.

Differential diagnosis.

Bensonella salwiniana differs from Bensonella species reported from Thailand and Laos in having a much larger (height 4-6 mm) and ovate conical shell, 6-7 whorls, inconspicuous palatal tubercle, and generally with six apertural dentitions. In contrast, B. nabhitabhatai , B. tamphathai and B. pangmapaensis tend to have smaller shells (height 2-4 mm), 4-5 whorls, a strong palatal tubercle, and generally bears 8-10 apertural dentitions ( Panha and Burch 2000, 2002b).

For further comparison, the three species from Laos, namely B. wangviangensis (Panha & Tongkerd, 2003), B. paralella (Inkhavilay & Panha, 2016), and B. anguloobtusa (Inkhavilay & Panha, 2016) possess a smaller shell (height 1-3 mm), a strongly developed palatal tubercle and generally bears 3-4 whorls ( Panha and Burch 2002b, 2005; Panha et al. 2003; Inkhavilay et al. 2016).

Although this species is very similar to B. gittenbergeri (Maassen, 2008) from Luang Namtha Province, Laos, in shell shape and size, it differs by having a lower palatal plica not extended to an expanded lip, a very narrow umbilicus, and an unextended palato-basal wall on the anterior side. In contrast, B. gittenbergeri possesses a long lower palatal plica that extends to an expanded lip, has a wider umbilicus, and its palato-basal wall is extended anteriorly ( Maassen 2008; Inkhavilay et al. 2016).

Bensonella salwiniana clearly differs from the two newly described species, B. lophiodera sp. nov. and B. taiyaiorum sp. nov., in having a larger shell (height 5-6 mm), and a broadly expanded peristome without cervical crest and lacking supra- and subcolumellar lamellae. Moreover, the latter two species possess smaller shells (height ~ 3 mm), a slightly expanded lip, and a conspicuous cervical crest. In addition, B. taiyaiorum sp. nov. has two upper palatal plicae, palatal tubercle strongly developed, supra-, subcolumellar lamellae and u-shaped plica present on the parietal wall, and a cervical crest far from the apertural lip. In contrast, B. lophiodera sp. nov. possesses a weakly expanded lip, subcolumellar lamella present and cervical crest close to apertural lip.

Remarks.

The species was described based on specimens received from F. Fedden (1839-1887). The specimens lacked a precise type locality, and only 'Shan States’ was stated in the original description. Although the type specimen could not be located, several recently collected and historical specimens were examined. This species possesses strongly developed parietal and angular lamellae, and lacks a tuba, which are the diagnostic characters of Bensonella .

The examined individuals either possess or lack an infraparietal lamella.

Figures

Figure 4. Bensonella salwiniana A specimen NHMUK 1912.4.16.66 from Burma B, C specimen CUMZ 14377 from Pyigyidagun Township, Mandalay Region D specimen CUMZ 14376 from Taunggyi District, Shan State E specimen CUMZ 14375 from Taunggyi District, Shan State F specimen CUMZ 14393 from Taunggyi District, Shan State. Abbreviations: a: angular lamella, b: basal plica, c: columellar lamella, ip: infraparietal lamella, lpl: lower palatal plica, p: parietal lamella, upl: upper palatal plica.

Figure 5. Bensonella salwiniana, specimen CUMZ 14397 from Taunggyi District, Shan State A genitalia and a small inset of penial appendix B preserved specimen with mantle edge, body and foot C snail showing colour in life D radula morphology: blue highlighting indicates central teeth and numbers indicate tooth order from lateral to marginal end. Abbreviations: at: atrium, e: epiphallus, fo: free oviduct, gd: gametolytic duct, gs: gametolytic sac, mc: mantle collar; p: penis, pa: penial appendix, pn: pneumostome; pr: penial retractor muscle, v: vagina, vd: vas deferens.

Figure 6. A Bensonella salwiniana, specimen CUMZ 14393 from Taunggyi District, Shan State B Bensonella anguloobtusa, specimen CUMZ 14401 from Taunggyi District, Shan State. Abbreviations: a: angular lamella, c: columellar lamella, itpl: interpalatal plica, lpl: lower palatal plica, p: parietal lamella, pt: palatal tubercle, 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.