Oospira shanensis Grego & Szekeres, 2021

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

11 Oospira shanensis Grego & Szekeres, 2021

Figs 3F , 12E, F , 14E-H , 15E , 19J

Oospira shanensis Grego & Szekeres in Szekeres et al. 2021a: 177, 178, fig. 8e, f. Type locality: “Shan” [Shan State, Myanmar].

Material examined.

Limestone outcrop at Nanthe Cave, Kalaw City, Shan State, Myanmar 20°35'16.6"N, 96°37'57.2"E: CUMZ 13060 (5 shells, Fig. 12E, F ), CUMZ 13061 (4 specimens in ethanol) .

Description.

Shell fusiform, opaque, and dark yellowish color; 5-6 apical whorls rapidly attenuated. Shell surface glossy and almost smooth; suture impressed and distinct. Whorls 12½ -13, last four whorls regularly growing and then rapidly attenuated to apex. Aperture obliquely or elliptical, basis oblique and broadest and narrowing towards parietal sinus; peristome attached, thickened, and expanded. Superior lamella developed, continuous with spiralis and indistinct at transition to spiralis. Inferior lamella steeply ascending, anterior end weakly visible in apertural view, very distant from superior lamella and ending at peristome. Subcolumellaris emerged and visible in oblique view. Principalis running along ventral-lateral side and anterior end visible through oblique apertural view. Palatal plicae ventral-lateral, five: equally spaced, fourth plica curved most, two middle plicae equally shorter than first and fourth; fifth plica can only be seen when shell is opened. Clausilium plate lateral side, broad, rounded and with hook.

Genitalia (n = 2). Atrium (at) small and short; penis (p) almost cylindrical and gradually narrower at transition to epiphallus. Epiphallus (ep) cylindrical and ca. same length and diameter as penis. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) very thin and shortly bounded at penis (Fig. 14E ). Internal sculpture of penis with 3 to 4 large corrugated longitudinal folds (Fig. 14G ). Internal sculpture of epiphallus with finely reticulated pattern arranged on two or three large longitudinal folds (Fig. 14H ).

Vagina (v) very thin and ~ 1/3 of free oviduct (fo) length. Distal part of pedunculus (dpb) long and enlarged, cylindrical; diverticulum (db) long, enlarged at basal and gradually reduced and becoming slender at terminal, and nearly same length as dpb; proximal part of pedunculus (ppb) short, ~ 3/4 diverticulum length, and bursa copulatrix (bb) small, ovoid (Fig. 14E ).

Radula. Central and lateral teeth contain ≥ 23 teeth with half-row formula: central-(lateral)-marginal teeth (1-(10-11)+). Central tooth tricuspid: mesocone large and triangular; ectocone small and located near the base. Lateral teeth bicuspid: endocone large and bluntly pointed tip; ectocone small and pointed tip. Marginal teeth asymmetrically tricuspid starting at approximately tooth number 10 or 11 (Fig. 15E ). Most marginal teeth part lost during the cleaning process.

Distribution.

This species is presently only known from Shan State, Myanmar.

Remarks.

Among all the Myanmar’s Oospira species studied herein, this is the only species with a clausilium hook (Fig. 12F ), and the clausilium plate is broader than in all other congeners. The presence of the hook in other phaedusinid taxa has been documented and is assumed to provide an advantage in trapping air bubbles to avoid drowning (see Páll-Gergely and Szekeres 2017).

Oospira sardicola can be distinguished from O. shanensis by having paler glossy yellowish color, wider and less oblique aperture, and less ventricose shell ( Szekeres et al. 2021b). This species can clearly be recognized from O. gouldiana and O. magna by its more ventricose shell, inferior lamella straight ascending and reduced to the peristome and clausilium more rounded, broader, and in lateral position. Moreover, O. shanensis has a relatively short male organ, epiphallus larger than the penis, diverticulum narrower to the proximal end, and the internal sculpture is distinctly different from O. gouldiana and O. magna .

Oospira mongmitensis , O. sardicola , and O. shanensis were recorded from Shan State. All of them are similar in possessing distinct palatal plicae which can be seen through the shell, but different in their pale to dark color, more or less bulging shell and aperture oblique to nearly vertical ( Szekeres et al. 2021a, b). Furthermore, O. sardicola and O. mongmitenis have distinct sutural papillae. These three species; O. mongmitensis , O. sardicola , and O. shanensis from Shan State are notably different from their congeners from southern Myanmar showing anterior end of inferior lamella reduced at peristome.

Our specimens show variation in the development of palatal plicae, especially as the fourth or fifth plicae are horizontal to oblique.

Figures

Figure 3. Living snails A Phaedusa shanica from Pyinyaung Village, Mandalay Region (SH ~ 14 mm) B Oospira philippiana from Kayon Cave, Mon State (SH ~ 22 mm) C Oospira bulbus from Sanbel Cave, Mon State (SH ~ 19 mm) D Oospira ovata from Pathein Mountain, Mon State (SH ~ 16 mm) E Oospira gouldiana from Kaw Ka Thuang Cave, Kayin State (SH ~ 26 mm) F Oospira shanensis from Nanthe Cave, Shan State (SH ~ 25 mm).

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 14. Genital anatomy of A-D Oospira magna, specimen CUMZ 13059 A whole reproductive system B internal sculpture of penis near atrium C internal sculpture of penis near epiphallus D internal sculpture of epiphallus and E-H Oospira shanensis, specimen CUMZ 13061 E whole reproductive system F overview 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 19. Synoptic view of the clausiliid species recorded from Myanmar A Phaedusa lypra, syntype MNHN-IM- 2000 - 2502 - 7 B Oospira magna, lectotype NHMUK 1901.3.17.156 C Oospira malaisei, holotype SMNH 3014 D Indonenia masoni, lectotype NHMUK 1888.12.4.1034 E Phaedusa bocki menglunanensis, specimen NHMUK 1903.7.1.3652 F Oospira mongmitensis, holotype UF 117571 (after Szekeres et al. 2021 b: fig. 1 d) G Oospira ovata, lectotype NHMUK 1906.2.2.378 H Oospira philippiana, possible syntype SMF 62294 / 1 I Oospira sardicola, holotype UF 117570 (after Szekeres et al. 2021 b: fig. 2 c) J Oospira shanensis, holotype NHMUK 1903.7.1.3544 K Phaedusa shanica, lectotype SMF 62260 L Oospira stoliczkana, holotype NHMUK 1888.12.4.1031 M Phaedusa theobaldi, lectotype NHMUK 1888.12.4.1056 N Phaedusa bocki thompsoni, specimen NHMUK 1903.7.1.1163 O Indonenia tuba, lectotype NHMUK 1907.12.30.241 P Oospira vespa, paralectotype MCZ 169456 and Q Oospira zediopsis sp. nov., holotype CUMZ 13064. Photo: P. Maestrati, MNHN (A), A Persson, SMNH (C).