Oospira andersoniana ( Moellendorff , 1882)

Man, Nem Sian, Lwin, Ngwe, Sutcharit, Chirasak & Panha, Somsak, 2023, Further notes on the taxonomy of the land snail family Clausiliidae Gray, 1855 (Stylommatophora, Helicina) from Myanmar with description of two new species, ZooKeys 1160, pp. 1-59 : 1

9 Oospira andersoniana ( Moellendorff, 1882)

Figs 12A, B , 13E-H , 15D , 18B

Clausilia (Pseudonenia) andersoniana Möllendorff, 1882: 12, pl. 1, fig. 13. Type locality: "In insula Mergui provincise Tenasserim" [Myeik Islands, Tanintharyi Region, Myanmar].

Clausilia [ Phaedusa (Pseudonenia) ] Phaedusa andersoniana - Gude 1914: 317.

Material examined.

The type specimens could not be located in the Senckenberg Museum, Frankfurt (K.-O. Nagel and S. Hof, pers. comm., April 2022). Phra Cave , Tanintharyi Region, Myanmar (11°13'46.2"N, 99°10'34.3"E): CUMZ 13056 (9 shells; Fig. 12A, B ), CUMZ 13057 (25 specimens in ethanol), JG-C2880 (2 shells) .

Description.

Shell fusiform, translucent, and pale yellowish brown color; spire regularly attenuated. Shell surface glossy and almost smooth surface; suture impressed and distinct. Whorls 9-10, little convex, regularly growing and attenuated to apex. Aperture pear-shaped, and basis broader and narrowing towards parietal sinus; peristome protruded, little thickened and expanded. Superior lamella developed, continuous with spiralis, and indistinct at transition to spiralis. Inferior lamella steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged and invisible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, 3-5 (usually 3): all plicae very strong, parallel, equal length, spacing, and one or two small plicae sometimes present in middle and at lowest. Clausilium plate lateral side and narrow.

Genitalia (n = 5). Atrium (at) short and slender; penis (p) almost cylindrical and shortly narrower at transition to epiphallus. Epiphallus (ep) cylindrical, ca. same length and diameter as penis. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) thin and shortly bounded at penis (Fig. 13E ). Internal sculpture of penis with smooth surfaces and with relatively thickened four or five longitudinal folds (Fig. 13F, G ). Internal sculpture of epiphallus with large and scattered papillae arranged obliquely to irregularly spaced rows (Fig. 13H ).

Vagina (v) thick, cylindrical, and almost equal to free oviduct (fo) length. Distal part of pedunculus (dpb) large and long; diverticulum (db) thin and ca. same length as dpb; proximal part of pedunculus (ppb) slender, nearly equal in length to diverticulum, and bursa copulatrix (bb) small, ovoid (Fig. 13E ).

Radula. Each row contains ~ 45 teeth with half-row formula: central-(lateral)-marginal teeth (1-(10-11)-22). Central tooth tricuspid: mesocone triangular with dull cusp; ectocones small and pointed tip. Lateral teeth bicuspid: endocone large and with dull cusp; ectocone small with tip pointed laterally. Marginal teeth asymmetrically tricuspid starting at approximately tooth number 10 or 11: endocone very tiny; mesocone large, elongate, blunt tip; ectocone small, triangular, pointed tip. Outermost becoming smaller and more asymmetrical than inner teeth (Fig. 15D ).

Distribution.

Currently O. andersoniana is only known from Tanintharyi Region, Myanmar.

Remarks.

This species was described based on two shells collected by the Scottish zoologist, John Anderson (1833-1900), approximately from southern Myanmar, and an illustration was included in the original publication ( Möllendorff 1882; Alcock 1902). Then, it was re-described and suggested to be very similar to O. gouldiana by Gude (1914). Despite the type specimen being mentioned in the type catalogue of the Clausiliidae in the Naturmuseum Senckenberg by Zilch (1954), this nominal species seems mysterious and is, therefore, listed as uncertain (taxon inquirendum) in MolluscaBase (2022). The type specimens of this species are presumably lost. However, Möllendorff (1882) provided a very detailed description and illustration of the species. Our newly collected specimens from the Tanintharyi Region have a thinly striated shell, smooth surface, thin peristome, mostly nine whorls and three palatal plicae, which matches well with the diagnostic characteristics of this species.

In this survey, Oospira andersoniana and O. stoliczkana were collected from the same locality in the Tanintharyi Region. These two species are similar in possessing a nearly smooth shell glossy surface, thin peristome, pale yellowish color, and less developed inferior lamella. However, O. stoliczkana exhibits a shorter, blunt spire, broader clausilium and several palatal plicae (from 8 to 10).

Compared with the other congeners, Oospira andersoniana can be distinguished from O. insignis , O. gouldiana , and O. magna by its less ventricose shell, smoother surface and pale color, peristome and inferior lamella weaker, and palatal plicae longer and more uniformly arranged. In contrast, O. insignis possesses oblique palatal plicae, more ventricose and darker colored shell, while O. gouldiana has a ventricose shell, spire more attenuated and with whitish apical whorls, inferior lamella more bent, aperture thicker and broader, and palatal plicae closer and more oblique. In addition, O. magna can be distinguished from O. andersoniana by having a finely and densely striated shell surface, inferior lamella well developed, clausilium in ventral position, and palatal plicae longer and more ventral (nearly horizontal). In terms of the genitalia, O. andersoniana has a short male organ, internal penis with large longitudinal folds and epiphallus with a distinct reticulated papillae pattern. In contrast, O. gouldiana and O. magna possess slender and longer male organs, internal penis with thinner and denser longitudinal folds, and epiphallus with irregularly arranged reticulated papillae patterns. Furthermore, O. limborgi Grego & Szekeres, 2021, also described from the Tanintharyi Region, shares some characteristics with this species in having the same number of palatal plicae, nearly triangular aperture, glossy and pale yellowish color (see Szekeres et al. 2021a: fig. 7c).

Shell variation was observed with respect to a small and short plica between the first and second palatal plicae.

Figures

Figure 12. Shell and clausilial apparatus of A, B Oospira andersoniana, specimen CUMZ 13056 from Phra Cave, Tanintharyi Region A shell B clausilial apparatus C, D Oospira magna, specimen CUMZ 13058 from Bayin Nyi Cave, Kayin State C shell D clausilial apparatus and E, F Oospira shanensis, specimen CUMZ 13060 from Nanthe Cave, Shan State E shell F clausilial apparatus. White arrows indicate principalis and yellow arrows indicate clausilium hook.

Figure 13. Genital anatomy of A-D Oospira gouldiana, specimen CUMZ 13049 A whole reproductive system B internal sculpture of penis C transition from penis to epiphallus D internal sculpture of epiphallus and E-H Oospira andersoniana, specimen CUMZ 13057 E whole reproductive system F overview of internal sculpture of penis and epiphallus G internal sculpture of penis H internal sculpture of epiphallus. Yellow arrows indicate approximate transitional position from penis to epiphallus.

Figure 15. Radula morphology A Oospira philippiana, specimen CUMZ 13039 B Oospira ovata, specimen CUMZ 13044 C Oospira gouldiana, specimen CUMZ 13049 D Oospira andersoniana CUMZ 13057 E Oospira shanensis, specimen CUMZ 13061. Blue color indicates central teeth row; yellow color indicates the transition from lateral to marginal teeth. ' C' indicates central tooth.

Figure 18. Synoptic view of the clausiliid species recorded from Myanmar A Indonenia admirabilis, holotype NHMUK 20200185 B Oospira andersoniana, specimen CUMZ 13054 C Oospira arakana, lectotype NHMUK 1888.12.4.1037 D Cylindrophaedusa bacillum, specimen NHMUK 1906.2.2.345 E Oospira bulbus, possible syntype NHMUK 1903.7.1.1278 F Phaedusa burmanica, holotype NHMUK 1888.12.4.1058 G Oospira decollata, paratype ZISP H Indonenia excellens, specimen NHMUK 20200189 I Oospira fusiformis, holotype NHMUK 1906.2.2.380 J Oospira gouldiana, lectotype NHMUK 196548 K Oospira gracilior, lectotype NHMUK 1907.12.30.243 L Oospira insignis, lectotype USNM 117120 M Phaedusa kazueae, holotype NHMUK 20200187 N Phaedusa lemani (after Gude, 1914: fig. 107) O Oospira limborgi, holotype NHMUK 1903.7.1.1266, and P Oospira luneainopsis sp. nov., holotype CUMZ 13062.