Oospira magna (Gude, 1914)

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

10 Oospira magna (Gude, 1914)

Figs 12C, D , 14A-D , 19B

Clausilia [ Phaedusa (Pseudonenia) ] Phaedusa gouldiana var. magna Gude, 1914: 316, fig. 109. Type locality: "Moulmain and Phaboo" [Mawlamyine, Mon State and Pabu, Hpa-an, Kayin State, Myanmar].

Materials examined.

Bayin Nyi Cave , Hpa-an Township, Kayin State, Myanmar (16°58'10.1"N, 97°29'30.6"E): CUMZ 13058 (3 shells + 6 incomplete shells, Fig. 12C, D ), CUMZ 13059 (1 specimen in ethanol) .

Description.

Shell fusiform, translucent, yellowish brown and 3-4 white apical whorls; spire regularly attenuated. Shell surface nearly smooth to with thin growth lines; suture deep and distinct. Whorls 10-11, convex, regularly growing and attenuated to apex. Aperture oval-pear-shaped, less oblique, basis broader and narrowing towards parietal sinus; peristome protruded, thickened, and slightly expanded. Superior lamella developed, continuous with spiralis, and indistinct at transition to spiralis. Inferior lamella well developed, steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged and invisible in oblique view. Principalis running along ventral-lateral side and anterior end visible through oblique apertural view. Palatal plicae ventral-lateral, 4-6 (usually 4): first plica strong and longest; second and third plicae short, parallel, oblique, and equal in length; fourth plica longer and stronger than middle plicae. Clausilium plate ventral side and narrow.

Genitalia (n = 1). Atrium (at) short and relatively large; penis (p) almost cylindrical and shortly narrower at transition to epiphallus. Epiphallus (ep) slender, ca. same length as penis and smaller diameter. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) almost same diameter as epiphallus and shortly bounded at penis (Fig. 14A ). Internal sculpture of penis with smooth surface and ca. four or five thin longitudinal rows (Fig. 14B ), and folds slightly enlarged near epiphallus (Fig. 14C ). Internal sculpture of epiphallus with large papillae arranged in oblique rows (Fig. 14D ).

Vagina (v) thick, cylindrical, and almost equal in length to free oviduct (fo). Distal part of pedunculus (dpb) cylindrical and long; diverticulum (db) very long, slightly enlarged at basis, then gradually slenderer, ~ 3 × times length of dpb; proximal part of pedunculus (ppb) slender, slightly short, ~ 3/4 diverticulum length; bursa copulatrix (bb) large, ovoid (Fig. 14A ).

Distribution.

Oospira magna is only recorded from the southern part of the country to the limestone area of the Salween River Basin in Mon and Kayin States, Myanmar.

Remarks.

Originally, Oospira magna was proposed as a subspecies of O. gouldiana based on its distinct less ventricose shell and seven palatal plicae ( Gude 1914). Later Szekeres et al. (2021b) recognized this as a morphological variation within the variable species, O. gouldiana . From our recent field survey, several specimens were collected, and their shell morphology matched well with the diagnostic characters of O. magna . Although O. magna is highly similar to O. gouldiana in shell form, it can be distinguished mainly by having a less ventricose shell, almost uniform and ventrally longer palatal plicae, more developed inferior spiral lamella, aperture less oblique, last whorl more compressed, spiralis starting deeply ventral, and clausilium ventrally seated. In genitalia, O. gouldiana exhibits a long distal part of pedunculus almost the same length as the proximal part of pedunculus and an internal sculpture of epiphallus with a thin and irregular corrugated pattern. These differences in the shell and genitalia characters are greater than the intraspecific variation and those characters were not observed as a morphological variation among the O. gouldiana populations examined; therefore, we have raised O. magna to a distinct species. Oospira zediopsis sp. nov. differ from O. magna by its a more ventricose shell with a smoother surface, apical whorl rapidly attenuated, dark reddish color, clausilium and palatal plicae laterally seated, and inferior lamella straight ascending.

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 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 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).