Clausilia corticina Pfeiffer, 1842, by subsequent designation of Martens in Albers (1860: 275).

Shell fusiform, more or less turreted, spire attenuated and shell surface with fine wavy to oblique striations. Palatal plicae short mostly, middle plicae weak to developed and 3 to 7 in number. Superior lamella low, connected to or separated from spiralis, and distinct at transition to spiralis. Inferior lamella spirally ascending and ending close to superior lamella from aperture view. Subcolumellaris visible or invisible in frontal view. Clausilium plate lateral side, rounded and broad.

Animal covered with reticulated, dark gray skin; tentacles short; body and tail with paler color on lateral margin of foot; foot moderately elongated, posteriorly obtusely pointed.

Nordsieck (2002b) compiled all the Southeast Asian Phaedusinae and summarized their diagnostic characteristics. Although Phaedusa and Loosjesia Nordsieck, 2002 are recognized as having spirally ascending inferior lamella, Phaedusa possesses shorter or weaker palatal plicae with the inferior lamella more narrowly spiral; in contrast, Loosjesia possesses longer and more developed palatal plicae, and much more spiral inferior lamella. Phaedusa closely resembles the Indian Cylindrophaedusa Boettger, 1877 (Gittenberger et al. 2019).

In the most recent generic classifications and species accounts by Grego et al. (2021) and Szekeres et al. (2021a, b), the genus Phaedusa from Myanmar is comprised of eight species, of which only three species were collected and re-described herein.

Limestone hills (Apache Cement Factory), Pyinyaung Village, Meiktila District, Mandalay Region, Myanmar (20°49'39.1"N, 96°23'35.1"E): CUMZ 13032 (6 shells Fig. 4A, B), CUMZ 13033 (40 specimens in ethanol), JG-C2881 (2 shells).

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 4. 

Shell and clausilial apparatus of A, B Phaedusa shanica, specimen CUMZ 13032 from Pyinyaung Village, Mandalay Region A shell B clausilial apparatus C, D Phaedusa burmanica, specimen CUMZ 13034 from Myin Ma Hti Cave, Shan State C shell D clausilial apparatus and E, F Phaedusa bocki menglunanensis, specimen CUMZ 13036 from Aik Kham Cave, Shan State E shell F clausilial apparatus. White arrows indicate principalis and yellow arrows indicate clausilium hook.

Shell fusiform, turreted, translucent, and pale yellowish brown; spire acute. Shell surface with thin and dense oblique striations; suture distinct. Whorls 11–13½, little convex, regularly growing and attenuated to apex, last whorl somewhat compressed. Aperture obliquely rounded to pear-shaped, basis rounded and narrowing towards parietal sinus; peristome slightly protruded, thickened, and expanded. Superior lamella low, continuous with spiralis, and very low at transition to spiralis to almost separated. Inferior lamella spirally ascending, close to superior lamella and ending at peristome. Subcolumellaris emerged and only visible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, three: first plica strong and longest; second plica very weak and close to first plica; third plica oblique from subcolumellaris and sometimes almost connected to second plica. Palatal plicae not visible without cracking shell. Clausilium plate lateral side, broad, rounded and slightly thickened at tip.

Genitalia (n = 5). Atrium (at) short; penis (p) muscular, cylindrical, and gradually narrower towards epiphallus. Epiphallus (ep) muscular, cylindrical, ca. same as penis length and size, and gradually widening to proximal end. Penial retractor muscle (pr) attached proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 5A). Internal sculpture of penis smooth-surfaced and with 3 to 5 longitudinal folds (Fig. 5B); at transition from penis to epiphallus with irregularly corrugated and wrinkled folds that randomly split and merge (Fig. 5C). Internal sculpture of epiphallus with large papillae arranged in oblique rows (Fig. 5D).

Figure 5. 

Genital anatomy of A–D Phaedusa shanica, specimen CUMZ 13033 A whole reproductive system B internal sculpture of penis C transition from penis to epiphallus D internal sculpture of epiphallus and E–G Phaedusa burmanica, specimen CUMZ 13035 E whole reproductive system F overview internal sculpture of penis and epiphallus G internal sculpture of proximal epiphallus. Yellow arrows indicate approximate transitional position from penis to epiphallus.

Vagina (v) slender at junction of atrium, then bulging at connection of free oviduct (fo) and distal part of pedunculus (dpb), and almost as long as free oviduct. Distal part of pedunculus large, long, and basally stouter; diverticulum (db) slender, nearly equal to dpb length; proximal part of pedunculus (ppb) large, long, measuring ~ 3/4 of diverticulum length, and bursa copulatrix (bb) ovoid (Fig. 5A).

Radula. Each row contains ~ 47 teeth with half-row formula: central–(lateral)–marginal teeth (1–(11–12)–23). Central tooth symmetrically tricuspid; mesocone large with pointed tip; ectocones triangular and located near the base. Lateral teeth asymmetrically bicuspid with small and pointed ectocone located at base; endocone large with pointed tip. Marginal teeth with asymmetrical tricuspids starting at approximately tooth number 11 or 12; mesocone large with dull tip; endocone and ectocone with small and pointed tips. Marginal teeth gradually reduced in size and becoming multicuspid marginally (Fig. 6A).

Figure 6. 

Radula morphology A Phaedusa shanica, specimen CUMZ 13033 and B Phaedusa burmanica, specimen CUMZ 13035. Blue color indicates the central teeth row; yellow color indicates the transition from lateral to marginal teeth. ‘C’ indicates central tooth.

Phaedusa shanica is collected from probably nearby the type locality and likely restricted in Myanmar. It appears to be quite abundant in the limestone hills based on the high numbers collected in our samplings.

Phaedusa shanica is very similar to P. theobaldi (Blanford, 1872) in having two or three palatal plicae which tend to connect at the second and third plicae. Phaedusa theobaldi (Fig. 19M) can be distinguished by its less turreted shell, coarser striations, darker horny color, superior lamella and spiralis separated, and not emerged subcolumellaris. These two species are difficult to distinguish at first sight; additional materials from the type locality and the genitalia of P. theobaldi, are required to elucidate the relationship between these two species.

Our specimens slightly differ from the type specimen in having three separated palatal plicae, or sometimes second and third plicae well developed and connected (Fig. 4B). According to Nordsieck’s (1974: fig. 6) drawing, the lectotype SMF 62260 has only two almost connected first and second palatal plicae, while the probable paralectotype as stated in Gude (1914: fig. 112) has palatal plicae pattern similar to the specimens examined herein. Therefore, we assume that the distinct or indistinct second plica might be attributed to morphological variation. Shell variations among the examined materials for P. shanica were observed, including slender to regular fusiform shell, oblique to subquadrate aperture, and the third plica may be well developed and reach to the second plica (Fig. 4B).

In addition, Phaedusa lypra (Mabille, 1887) from Shan State also resembles this species in shell form; however, P. lypra has a blunter spire, less turreted shell, and wider aperture sinus (Szekeres et al. 2021a: fig. 10f). Phaedusa burmanica (Gude, 1914) and P. bocki menglunanensis (Luo, Cheng & Zhang, 1998) from Shan State differ from P. shanica in having a larger shell, five distinct palatal plicae that can be seen from outside of shell, wavier and coarser shell surface, and clausilium with a hook (Fig. 4). Regarding the genitalia, P. shanica possesses more simple and smooth longitudinal folds and reticulated papillae in the epiphallus, while P. burmanica has strongly wavy, irregularly dense, and crowded longitudinal folds along the epiphallus with a distinct fold near the vas deferens (Fig. 5).

Myin Ma Hti Cave, Kalaw City, Shan State, Myanmar (20°35'26.1"N, 96°36'42.6"E): CUMZ 13034 (2 shells + 1 incomplete shell; Fig. 4C, D), CUMZ 13035 (1 specimen in ethanol).

Shell fusiform, turreted, translucent, and pale chestnut-brown; spire acute. Shell surface glossy with thin and dense striations; suture distinct. Whorls 12–13, little convex, regularly growing and attenuated to apex; last whorl compressed. Aperture vertically subquadrate, basis rounded and narrowing towards parietal sinus; peristome slightly protruded, thickened, and expanded. Superior lamella low, continuous with spiralis, and very low at transition to spiralis. Inferior lamella spirally ascending, close to superior lamella and ending at peristome. Subcolumellaris emerged, and visible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, distinctly five: first plica strong, longest, and nearly connected to principalis anteriorly; second and fifth plicae almost equal and slightly strong; third and fourth plicae weakest and almost not visible. Palatal plicae visible through translucent shell. Clausilium plate lateral side, broad, rounded and with hook.

Genitalia (n = 1). Atrium (at) short and slender; penis (p) muscular, cylindrical, broadest at middle part and gradually narrower towards epiphallus. Epiphallus (ep) muscular, cylindrical, ca. same length and size as penis, gradually enlarging to proximal end. Penial retractor muscle (pr) attached proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 5E). Internal sculpture of penis smooth-surfaced and slightly wavy with ca. four longitudinal folds (Fig. 5F). Internal sculpture of epiphallus generally defined as two parts: region near penis with wavy longitudinal folds, then gradually becoming more densely crowded towards proximal epiphallus; region near vas deferens with strong folds and papillae arranged in oblique rows (Fig. 5G).

Vagina (v) slender at junction of atrium, then bulging at connection of free oviduct (fo) and distal part of pedunculus (dpb), and almost as long as free oviduct. Distal part of pedunculus large, long, basally stouter, and broadest near entrance of diverticulum; diverticulum (db) large, as long as dpb; proximal part of pedunculus (ppb) large, measuring ~ 1/2 diverticulum length, and bursa copulatrix (bb) ovoid (Fig. 5E).

Radula. Each row contains ~ 51 teeth with half-row formula: central–(lateral)–marginal teeth (1–(13–14)–25). Central tooth small, symmetrically tricuspid; mesocone large with dull tip; ectocones very small. Lateral teeth asymmetrically bicuspid: endocone large and with dull tip; ectocone very small, pointed tip and located near the base. Marginal teeth tricuspid starting at approximately tooth number 13 or 14; mesocone long and dull tip; endocone very small and located near tip of mesocone; ectocone small with pointed tip. Marginal teeth gradually becoming polycuspid towards radula margin (Fig. 6B).

Apart from the type locality, this species is widely known from Bhamo, Kachin State (Gude 1914) to Shan State and the Mandalay Region in Myanmar (Grego et al. 2021).

Phaedusa bocki menglunanensis from Shan State can be distinguished from this species by its inferior lamella less spirally ascending, palatal plicae longer, obliquely arranged and more spaced between them, shell surface finer and more curved striations, aperture vertically quadrate, and subcolumellaris distinctly visible in frontal view. Phaedusa bocki thompsoni Grego & Szekeres, 2021 also differs from this species in having a more vertical aperture, acute spire, and palatal plicae more on dorsal side (see Szekeres et al. 2021a: fig. 9f).

Variation was observed among the examined specimens in having the superior lamella and spiralis either separated or connected.

Aik Kham Cave, Taunggyi City, Shan State, Myanmar (20°49'7.0"N, 97°13'42.0"E): CUMZ 13036 (3 incomplete shells, Fig. 4E, F).

Shell fusiform, translucent, and pale yellowish brown; spire regularly acute. Shell surface with fine and coarse striations; suture wide and distinct. Whorls 12 and 13 nearly flattened, regularly increasing, and attenuated to apex. Aperture vertically subquadrate, basis rounded and narrowing towards parietal sinus; peristome protruded, expanded and little reflexed. Superior lamella low, continuous with spiralis, and low at transition to spiralis. Inferior lamella spirally ascending, slightly horizontal before reaching peristome and close to superior lamella. Subcolumellaris emerged, ending at peristome margin, and clearly visible in frontal view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, four or five: first plica distinct, longest, and nearly connected to principalis anteriorly; second plica ~ 1/2 of first plica length and remaining plicae oblique, equally spaced, and shorter. Palatal plicae visible through translucent shell. Clausilium plate lateral side, broad, rounded, and with hook.

Phaedusa bocki menglunanensis was originally described from Yunnan Province, China, which is near the borders with Vietnam and Laos. It was recently found in Shan State, along the Mekong River near the border with Laos (Szekeres et al. 2021a).

No preserved specimens were found for examination of the genitalia. This subspecies and samples of P. bocki thompsoni collected from the same geographical range have a similar shell morphology, but P. bocki thompsoni has invisible subcolumellaris in frontal view, blunter and turreted spire, and whorls after antepenultimate whorl rapidly attenuated (see Szekeres et al. 2021a: fig. 9f). However, the holotype of P. bocki thompsoni from Thailand possesses a subcolumellaris that is visible in frontal view, and four to seven plicae that become shorter and somewhat diffuse towards the base (Szekeres et al. 2021b: fig. 2d). More materials are required for comparison to determine whether the differentiating characters are consistently distinct between these two subspecies.

Clausilia philippiana Pfeiffer, 1847, by original designation.

Shell short to long fusiform, shell surface smooth to with striated ridges, spire blunt to attenuated, whorls few to numerous (6–13). Palatal plicae short to long, mostly developed and 3–10 in number. Superior lamella developed, usually connected to spiralis, distinct or indistinct at transition to spiralis. Inferior lamella steeply ascending and somewhat ending distant from superior lamella in aperture view. Subcolumellaris usually invisible in frontal view; clausilium plate lateral to ventral side and usually narrow.

Living animals possess reticulated skin; dark gray head; short tentacles; body and tail pale to dark brownish; foot moderately elongated, posterior nearly rounded to bluntly pointed.

Oospira is the most species-rich genus of the Phaedusinae, and more than a hundred species have been reported from a broad range in Southeast Asia (MolluscaBase 2022). Nordsieck (2002b) united two previously recognized genera, Acrophaedusa Boettger, 1877 and Pseudonenia Boettger, 1877 to form Oospira based on their shared steeply ascending inferior lamella, normal clausilium plate, and mostly palatal plicae form. Perhaps this grouping causes Oospira to become widely diverged in shell shape from ovate to fusiform, dark brown to pink, and different aperture shapes which is thought to be a homoplasy. A phylogenetic analysis of phaedusinids genera from Japanese and some southeast Asian taxa, especially from Vietnam, was not in line with traditional taxonomy probably due to parallel or convergent evolution (Motochin et al. 2017; Mamos et al. 2021). However, none of the Indochinese taxa, including Oospira, were explored in this phylogenetic work.

The genera Loosjesia from Thailand, Messageriella Páll-Gergely & Szekeres, 2017 and Castanophaedusa Páll-Gergely & Szekeres, 2017 from Vietnam, Musaphaedusa Nordsieck, 2018 from Laos, and Oospira have a similar shell morphology, especially in the form of the palatal plicae. However, Loosjesia can readily be differentiated by its predominantly curved basal inferior lamella with a long transverse palatal plica and clearly visible subcolumellaris (Loosjes 1953; Nordsieck 2002b). Messageriella is distinguished by its marginally ending inferior lamella and subcolumellaris, palatal plicae non-parallel and ventral (Páll-Gergely and Szekeres 2017); similarly, Castanophaedusa has a rhomboidal aperture which extends to the columellar side and sharply bent basis, marginal and strongly emerged subcolumellaris, palatal plicae ventral and parallel to the principalis (Páll-Gergely and Szekeres 2017). Meanwhile, Musaphaedusa has strong sutural papillae, principalis very long, palatal plicae ventral (only two) and strong rib-like striations on the shell surface (Nordsieck 2018).

Regarding the reproductive anatomy of this group, Oospira penangensis (Stoliczka, 1873) and O. philippiana were the first species examined for their genitalia (Stoliczka 1871, 1873). At present, seven species (including O. decollata and O. malaisei from Myanmar) have been investigated (Loosjes 1953; Likharev 1962; Nordsieck 1973; Maassen and Gittenberger 2007; Páll-Gergely and Szekeres 2017).

Based on shell morphology, we have divided Oospira from Myanmar into two species groups comprised of those with (i) short and ovate fusiform shells and (ii) long and slender fusiform shells. The short and ovate fusiform group includes the species believed to be Oospira s.s. (type species Clausilia philippiana Pfeiffer, 1847), while the long and slender fusiform group assumed to be the species previously known as ‘Pseudonenia Boettger, 1877’ (type species Clausilia javana Pfeiffer, 1841).

Possible syntype SMF 62294/1 ex. H. Dohrn collection from Burma: [Mergui] (Fig. 7A). Saddan Cave, ~ 600 m south of Kayon Cave, Mawlamyine Township, Mawlamyine District, Mon State, Myanmar (16°31'42.8"N, 97°43'2.1"E): CUMZ 13037 (10 adults + 5 juveniles, Fig. 7C). Kayon Cave [formerly called Farm Caves] ~ 10 km from Mawlamyine Township, Mawlamyine District, Mon State, Myanmar (16°32'0.5"N, 97°42'53.5"E): CUMZ 13038 (6 shells; Fig. 2), CUMZ 13039 (15 specimens in ethanol). Pha Boang Cave from Mawlamyine Township, Mawlamyine District, Mon State, Myanmar (16°17'14.04"N, 97°54'4.28"E): CUMZ 13040 (9 adults + 9 juveniles, Fig. 7B), CUMZ 13041 (15 specimens in ethanol).

Figure 7. 

Shell and clausilial apparatus of A–C Oospira philippiana A possible syntype SMF 62294/1 from Burma B clausilial apparatus, specimen CUMZ 13040 from Pha Boang Cave, Mon State C shell, specimen CUMZ 13037 from Saddan Cave, Mon State and D–F Oospira bulbus, specimen CUMZ 13042 from Sanbel Cave, Mon State D clausilial apparatus E, F shells. White arrow indicates principalis.

Shell ovate-fusiform, opaque, and chestnut-brown color; spire blunt. Shell surface nearly smooth or with very thin striations; suture distinct. Whorls 5–6½, convex, regularly growing and bluntly attenuated to apex. Aperture obliquely pear-shaped, basis broader and narrowing towards parietal sinus; peristome detached, thickened, expanded and little reflexed. Superior lamella developed, continuous with spiralis, and low at transition to spiralis. Inferior lamella steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged, and only visible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, 7–9: first plica strong and longest; following plicae shorter, parallel, nearly equal in length, gradually reduced towards anterior. Clausilium plate lateral side, slightly broad and rounded at tip.

Genitalia (n = 5). Atrium (at) short and slender; penis (p) muscular and cylindrical. Epiphallus (ep) muscular, cylindrical, ca. same length and half of the diameter of penis and broadest at middle part. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 8A). Internal sculpture of penis consists of two parts: region near atrium ~ 1/3 of penis length with series of irregular transverse folds, chevron-shaped; region near epiphallus becoming smooth surface and relatively thick with 5–7 longitudinal folds (Fig. 8B). Internal sculpture of epiphallus with elevated papillae arranged in oblique rows (Fig. 8C).

Figure 8. 

Genital anatomy of A–C Oospira philippiana, specimen CUMZ 13039 A whole reproductive system B internal sculpture of penis C internal sculpture of epiphallus and D–F Oospira bulbus, specimen CUMZ 13043 D whole reproductive system E internal sculpture of penis F internal sculpture of epiphallus. Yellow arrows indicate approximate transitional position from penis to epiphallus.

Vagina (v) thick and very short, ~ 1/3 of free oviduct (fo) length. Distal part of pedunculus (dpb) large and long; diverticulum (db) long, ~ 2× length and slightly larger diameter than dpb; proximal part of pedunculus (ppb) slender, ca. equal in length to diverticulum, and bursa copulatrix (bb) with distinct ovate shape (Fig. 8A).

Radula. Each row contains ≥ 39 teeth with half-row formula: central–(lateral)–marginal teeth (1–(11–12)–19+). Central tooth unicuspid with rounded to blunt tip. Lateral teeth bicuspid: endocone large and rounded tip; ectocone very small, pointed tip and located near the base. Marginal teeth asymmetrically tricuspid starting at approximately tooth number 11 or 12: mesocone large and curved to blunt tip; endocone small and located near tip of mesocone; ectocone triangular, pointed tip and located near the base. Outermost teeth have been lost during the preparation process (Fig. 15A).

In Myanmar, this species is reported from Kayin, Mon and Tanintharyi (Gude 1914; Szekeres et al. 2021a, b). In addition, the records outside Myanmar are from Kanchanaburi Province, Thailand (Szekeres et al. 2021b), and further in Andaman Islands, but mentioned as dubious record (see Szekeres et al. 2021a: 177). In this survey, three populations were collected from isolated limestone karsts in Salween River Basin with relatively high abundance.

Oospira stoliczkana can be distinguished from O. philippiana by its elongate ovoid shell, pale color, and higher numbers of plicae. In terms of the genital organs, the male internal sculpture of O. philippiana has thicker and denser corrugated folds near the atrium than in O. stoliczkana (Fig. 10F). Moreover, O. vespa can be differentiated from this species by having an acute spire, aperture more oblique and broader, whorls more expanded.

Among the examined specimens, those from the Pha Boang Cave population (24 shells) have larger and darker shells with more widely spaced and up to nine developed palatal plicae. In contrast, specimens from the Kayon Cave (21 shells) and Saddan Cave (15 shells) populations are uniform in terms of a smaller shell and seven closer and weaker plicae (Table 1).

No specimens were found at the type locality ‘Mergui’ [Myeik]; but Szekeres et al. (2021b) reported material from Tanintharyi Region. Instead, multiple populations with high abundance were collected in the vicinity of Salween River Basin in this present study (Fig. 1; Table 1). This agreed with Stoliczka’s (1871: 175) statement that the species was ‘common at the Farm-caves near Moulmein on limestone hills’.

Sanbel Cave, Mawlamyine Township, Mon State, Myanmar (16°22'26.0"N, 97°46'22.6"E): CUMZ 13042 (15 shells; 7D–F), CUMZ 13043 (3 specimens in ethanol), JG-C2882 (1 shell).

Shell oblong-ovate, translucent, and brownish; spire rounded and almost flatted to apex. Shell surface with fine and distinct striations; suture wide and distinct. Whorls 5–5½; penultimate whorl rapidly growing and largest; last whorl compressed and narrower. Aperture obliquely pear-shaped, basis rounded and narrowing towards parietal sinus; peristome detached, thickened, slightly expanded, and not reflexed. Superior lamella sharp, oblique, continuous with spiralis, and low 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, five: first plica longest; following four plicae parallel, equal in length and spacing, and slightly reduced towards anterior. Clausilium plate lateral side and narrow.

Genitalia (n = 2). Atrium (at) short and slender; penis (p) muscular and cylindrical. Epiphallus (ep) muscular, cylindrical, ca. same length and half diameter of penis, and broadest at middle part. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 8D). Internal sculpture of penis consists of two parts: region near atrium and ~ 1/2 of penis length with series of irregular transverse folds, chevron-shaped; region near epiphallus becoming smooth, with 5–7 slightly wavy longitudinal folds (Fig. 8E). Internal sculpture of epiphallus with elevated papillae arranged in oblique rows (Fig. 8F).

Vagina (v) thick and short, ~ 1/2 of free oviduct (fo) length. Distal part of pedunculus (dpb) large and long; diverticulum (db) long, ~ 2× in length and slightly smaller in diameter than dpb; proximal part of pedunculus (ppb) slender, ca. equal in length to diverticulum and bursa copulatrix (bb) with distinct ovate shape (Fig. 8D).

Oospira bulbus has only been reported from Myanmar and is possibly endemic in the limestone hills along the lower course of Attaran River. The specimens examined herein were collected near the type locality.

Oospira ovata can be separated from this species by its a smoother striated shell, attenuated spire and usually seven plicae. In terms of the genital organs, the male internal sculpture of O. ovata has longer V-shaped folds in the region near the atrium and rounded papillae in epiphallus than this species. Although O. bulbus has a similar shell form to Atractophaedus pyknosoma (Gittenberger & Vermeulen, 2001) from Vietnam, A. pyknosoma has a narrower spire, visible subcolumellaris in frontal view, peristome reflected with nearly double lip and first palatal plicae shorter than the following plicae (see Gittenberger and Vermeulen 2001: figs 1–10).

Pathein Mountain, Mawlamyine Township, Mon State, Myanmar (16°14'7.5"N, 97°56'48.1"E): CUMZ 13044 (25 shells, Fig. 9A–C), CUMZ 13045 (1 specimen in ethanol), JG-C2883 (2 shells).

Figure 9. 

Shell and clausilial apparatus of A–C Oospira ovata, specimen CUMZ 13044 from Pathein Mountain, Mon State A, C shells B clausilial apparatus and D–F Oospira stoliczkana, specimen CUMZ 13046 from Phra Cave, Tanintharyi Region D clausilial apparatus E, F shells. White arrows indicate principalis.

Shell ovate or pupiform, opaque and chestnut-brown; spire blunt. Shell surface nearly smooth or with very thin growth lines; suture distinct. Whorls 5–5½ convex, rapidly growing; penultimate and antepenultimate whorls equally broad and rounded to apex. Aperture obliquely pear-shaped, basis rounded and narrowing towards parietal sinus; peristome detached, thickened, expanded and little reflexed. Superior lamella well developed, continuous with spiralis and low at transition to spiralis. Inferior lamella steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged and only visible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, six or seven: first plica strong and longest; following plicae short, parallel, equal in length and gradually reduced towards anterior. Clausilium plate lateral side and narrow.

Genitalia (n = 1). Atrium (at) short and slender; penis (p) muscular and cylindrical. Epiphallus (ep) muscular, cylindrical, ~ 1.5× diameter of penis, and broadest close to penis. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) slender and shortly bounded at atrium and penis junction (Fig. 10A). Internal sculpture of penis consists of two parts: region near atrium, ~ 2/3 of penis length with moderately thick transverse folds arranged in V-shaped rows; region near epiphallus with smooth surface and four or five longitudinal folds (Fig. 10B, C). Internal sculpture of epiphallus with rounded papillae arranged in oblique rows (Fig. 10D).

Figure 10. 

Genital anatomy of A–D Oospira ovata, specimen CUMZ 13045 A whole reproductive system B internal sculpture of penis C transition from penis to epiphallus D internal sculpture of epiphallus and E–H Oospira stoliczkana, specimen CUMZ 13047 E whole reproductive system F internal sculpture of penis G transition from penis to epiphallus H internal sculpture of epiphallus. Yellow arrows indicate approximate transitional position from penis to epiphallus.

Vagina (v) thick, short, and almost half of free oviduct (fo) length. Distal part of pedunculus (dpb) large and long; diverticulum (db) large, slightly longer, and larger in diameter than dpb; proximal part of pedunculus (ppb) slender, ~ 2/3 diverticulum length and bursa copulatrix (bb) with distinct ovate shape (Fig. 10A).

Radula. Each row contains ~ 61 teeth with half-row formula: central–(lateral)–marginal teeth (1–(12–13)–26). Central tooth unicuspid with dull tip. Lateral teeth bicuspid; endocone large with curved to dull tip; ectocone very tiny to small and pointed tip. Marginal teeth asymmetrically tricuspid starting at approximately tooth number 12 or 13: mesocone large and dull tip; ectocone and endocone small with pointed tips. Outer marginal teeth increasingly asymmetrical and shorter than inner marginal teeth (Fig. 15B).

At present, O. ovata is only known from Myanmar. Many shells were collected in this study; it is likely endemic to the valley of Attaran River.

Oospira ovata and O. philippiana are generally similar in shell morphology, but O. ovata has a more expanded spire. The male internal sculpture of O. ovata has longer V-shaped folds in the region near the atrium and rounded papillae pattern in epiphallus, whereas O. philippiana has shorter V-shaped folds and more elevated and pointed papillae in epiphallus.

Phra Cave, Tanintharyi Region, Myanmar (11°13'46.2"N, 99°10'34.3"E): CUMZ 13046 (4 shells; Fig. 9D–F), CUMZ 13047 (1 specimen in ethanol).

Shell elongate ovoidal, glossy, translucent, and horny brown; spire blunt. Shell surface with very thin striations to smooth surface; suture wide and distinct. Whorls 6–6½, convex, regularly growing and bluntly attenuated to apex. Aperture obliquely pear-shaped, basis rounded and narrowing towards parietal sinus; peristome detached, thin and little expanded. Superior lamella developed, sharp, continuous with spiralis and low at transition to spiralis. Inferior lamella steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged and only visible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, 8–10: first plica strong and longest; following four plicae parallel and equal in length, and remaining plicae shorter, closer, gradually reduced towards anterior. Clausilium plate lateral side and slightly broad at tip.

Genitalia (n = 1). Atrium (at) short and slender; penis (p) muscular and cylindrical. Epiphallus (ep) muscular, cylindrical, slightly longer by 1.5× diameter of penis, and broadest at proximal part. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 10E). Internal sculpture of penis consists of two parts: region near atrium, ~ 1/4 length of penis with irregular transverse fleshy folds arranged in nearly V-shaped rows (Fig. 10F); region near epiphallus becoming smooth with oblique longitudinal folds (Fig. 10G). Internal sculpture of epiphallus with elevated papillae arranged in nearly oblique rows (Fig. 10H).

Vagina (v) large, short, and almost half the length of free oviduct (fo). Distal part of pedunculus (dpb) large and long; diverticulum (db) long, ca. same length as dpb; proximal part of pedunculus (ppb) slender, almost equal in length to diverticulum, and bursa copulatrix (bb) small, ovateshape (Fig. 10E).

This species is known from Mon State, along with its type locality in Tanintharyi Region; no reports have been made outside Myanmar to date (Szekeres et al. 2021a).

Oospira stoliczkana can be distinguished from all other species with an ovate-fusiform shell (O. philippiana, O. ovata, O. bulbus, and O. vespa) by its elongate ovoidal shell, thinner peristome, and 8 to 10 palatal plicae. Although only one ethanol-preserved specimen could be examined, the internal sculpture of the penis and epiphallus of O. stoliczkana differs from O. philippiana, O. bulbus, and O. ovata by its very short V-shaped folds in the region near the atrium and more elevated and pointed papillae in epiphallus.

Some of the examined specimens had a thin and translucent shell, with more distinct palatal plicae.

Bardai Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°59'10.4"N, 97°42'19.8"E): CUMZ 13048 (25 specimens in ethanol, Fig. 11A–C). Kaw Ka Thaung Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°49'40.4"N, 97°42'31.0"E): CUMZ 13049 (23 specimens in ethanol, Fig. 11D). Lun Nga Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°44'53.2"N, 97°47'09.5"E): CUMZ 13050 (18 specimen in ethanol). Sadhdan Cave, Hpa-an Township, Hpa-District, Kayin State, Myanmar (16°44'23.4"N, 97°43'04.2"E): CUMZ 13051 (2 incomplete shells). Taung Lay Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (17°11'40.3"N, 97°37'47.0"E): CUMZ 13052 (30 shells; Fig. 11E). Waiponla Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°56'7.4"N, 97°42'56.8"E): CUMZ 13053 (2 incomplete shells, Fig. 11F), CUMZ 13054 (2 specimens in ethanol, lost apical whorls). Rathye Pyan Cave, Hpa-an Twonship, Hpa-an District, Kayin State, Myanmar (16°50'6.2"N, 97°34'14.5"E): CUMZ 13055 (1 incomplete shell).

Figure 11. 

Shell and clausilial apparatus of Oospira gouldiana A–C specimen CUMZ 13048 from Bardai Mountain, Kayin State A typical pinkish shell form B clausilial apparatus C not fully adult shell D yellowish shell form, specimen CUMZ 13049 from Kaw Ka Thaung Cave, Kayin State E slender shell form, specimen CUMZ 13052 from Taung Lay Cave, Kayin State F ovate shell form, specimen CUMZ 13053 from Waiponla Mountain, Kayin State. White arrow indicates principalis.

Shell fusiform, translucent, brownish to reddish pink, and 3–4 white apical whorls; spire regularly attenuated. Shell surface finely striated to nearly smooth surface; suture impressed and distinct. Whorls 10–12 convex, regularly growing or sometimes rapidly growing after antepenultimate whorl and attenuated to apex. Aperture pear-shaped, basis broader and narrowing towards parietal sinus; peristome slightly protruded, thickened, expanded, and indistinctly doubled. Superior lamella developed, continuous with spiralis and slightly low 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, five or six: first plica strong and longest; following plicae short, more or less parallel; fourth or fifth plica longer than middle plicae. Clausilium plate lateral side and narrow.

Genitalia (n = 5). Atrium (at) short and slender; penis (p) long, slender, and shortly narrower at transition to epiphallus. Epiphallus (ep) slender, ca. same length as penis, slightly smaller diameter, and broadest at middle. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) thin and shortly bounded at penis (Fig. 13A). Internal sculpture of penis with smooth surfaces and five or six thin longitudinal folds (Fig. 13B). Internal sculpture of epiphallus with irregular corrugated pattern (Fig. 13D) and sometimes with distinct irregular transverse fold and papillae arranged in oblique rows.

Vagina (v) thick, cylindrical, and almost half of free oviduct (fo) length. Distal part of pedunculus (dpb) large and middle part broadest; diverticulum (db) slender, very long, ca. same length as distal part and proximal part of pedunculus; proximal part of pedunculus (ppb) slender, nearly same length as (dpb), and bursa copulatrix (bb) ovoid (Fig. 13A).

Radula. Each row contains ≥ 39 teeth with half-row formula: central–(lateral)–marginal teeth (1–(11–12)–19). Central tooth tricuspid with large and triangular mesocone, and ectocones very small and pointed tips. Lateral teeth bicuspid: endocone large and triangular; ectocone very small and pointed tip. Marginal teeth asymmetrically tricuspid starting at approximately tooth number 11 or 12: endocone small located near the tip; mesocone large and dull to blunt tip; ectocone with triangular shape, pointed tip and located near the base (Fig. 15C).

Oospira gouldiana is the most abundant species of the genus in Myanmar, occurring mainly in the south-eastern part of the country. This species was abundant at seven limestone outcrops in Kayin State (Fig. 1, Table 1). It was recorded from Bago, Kayin, Mon, and Tanintharyi in Myanmar, and the distribution was later expanded to include parts of Thailand (Gude 1914; Szekeres et al. 2021a, b).

Oospira gouldiana specimens from Taung Lay Cave are quite similar to O. malaisei from Kachin State in terms of shell form. But O. malaisei (Fig. 17C) shows a more vertical and broader aperture, reflected peristome, closely and rapidly attenuated apical whorls, and inferior lamella more straight ascending at peristome. In contrast, Taung Lay Cave specimens have an oblique and rounded aperture, less reflected peristome, regularly attenuated whitish apical whorls and inferior lamella more spirally ending at peristome. Anatomically, O. malaisei possesses an epiphallus of ~ 1/2 the penis length, while in O. gouldiana epiphallus and penis have almost equal lengths (see Nordsieck 1973: fig. 26).

Oospira gouldiana also shares a similar shell morphology with O. insignis exhibiting a regularly attenuated spire with whitish apical whorls, palatal plicae five, and a broad pear-shaped aperture. Nevertheless, O. gouldiana has a more attenuated spire, more parallel palatal plicae, aperture more vertical, and less glossy than O. insignis. In addition, this species can easily be separated from O. shanensis by its pale color, shorter and oblique palatal plicae, inferior lamella more spirally and closely ascending from spiralis and superior lamella. Oospira penangensis differs from this species by its less ventricose, narrower, and more vertical subquadrate aperture, inferior lamella ending straight at peristome and weaker superior lamella from apertural view.

Oospira gouldiana is highly variable in terms of shell color and shape. The typical form was found in the Bardai and Kaw Ka Thaung populations, showing a yellowish to pinkish color with a regular fusiform shape (Fig. 11A, D), while the Taung Lay population have a slenderer shell and the Waiponla population have a more bulging shell (Fig. 11E, F). In addition, the arrangement of palatal plicae shows much variation among the populations. For instance, the Bardai population has irregularly or obliquely arranged plicae (nearly vertical), Kaw Ka Thaung population has parallelly arranged plicae, while the Waiponla and Lun Nga populations have very weak and short parallelly arranged palatal plicae. Furthermore, a very short plica (dot-like) located near the anteriormost palatal plicae next to subcolumellaris is also observed in the Bardai population.

Except for the Sadhdan, Taung Lay, and Rathye Pyan populations, for which genitalia could not be examined, the remaining populations are similar in external genital morphology, with only slightly differing thickness of the longitudinal folds of the internal sculpture of the penis being observed. However, these four populations inhabit a very small geographical area, hence we attribute this minor difference to morphological variation.

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).

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.

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).

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.

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).

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

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.

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).

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).

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.

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).

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.

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.

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).

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.

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.

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

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.

Holotype CUMZ 13062 (Fig. 16A). Measurements: shell height 20 mm, shell width 5.8 mm, and 7 whorls. Paratypes CUMZ 13063 (8 shells; Fig. 16B, C), NHMUK 20220504 (2 shells).

Figure 16. 

Shell and clausilial apparatus of A–C Oospira luneainopsis sp. nov. A shell of holotype CUMZ 13062 from Zwekabin Mountain, Kayin State B, C paratypes CUMZ 13063 from the type locality B clausilial apparatus C shell and D–F Oospira zediopsis sp. nov. D clausilial apparatus of paratype CUMZ 13065 from the type locality E shell of holotype CUMZ 13064 from Weibyan Cave, Kayin State and F shell of paratype CUMZ 13065 from the type locality.

Limestone outcrop at Zwegabin Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°48'44.5"N, 97°40'25.5"E).

The specific name luneainopsis is a compound of ‘lun-eain’, which in the Myanmar language refers to a bobbin used for traditional Myanmar weaving, and the Greek suffix -opsis meaning ‘having the appearance of or like’. It refers to the bobbin shape of the shell of this species.

Figure 17. 

Shell of A Oospira decollata, paratype ZISP from West Burma, near Pakoku on Mount Victoria. 2200 m a.s.l. B Oospira insignis, lectotype USNM 117120 from Tavoy, Burmah C Oospira malaisei, holotype SMNH 3014 from NO-Birma: Pungkataung ca. 3000 ft. and D Oospira vespa, lectotype MCZ 169455 from Tavoy, British Burma. Photo: A Persson, SMNH (C).

Shell ovate-fusiform, decollated with smooth surface and dense striations near suture. Last whorl neck subquadrate; aperture nearly roundish; peristome detached. Inferior lamella straight ascending and reaching at peristome; palatal plicae four, distinct, equally, and parallelly arranged, and superior lamella developed.

Shell ovate-fusiform, decollated, opaque, pinkish brown; spire blunt. Shell surface smooth to with fine growth lines on last whorl, denser near suture and last whorl neck subquadrate; suture impressed and distinct. Whorls 7–8, convex, regularly growing, and bluntly attenuated to apex. Aperture nearly round; peristome detached, thickened, expanded and little reflexed. Superior lamella developed, continuous with spiralis, and slightly low 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, four: first and fourth plicae strong and longest; remaining plicae parallel and equal length; sometimes tiny lowest plica present. Clausilium plate lateral side, narrow and slightly pointed at tip.

Oospira luneainopsis sp. nov. is only known from the type locality.

No ethanol preserved specimens were available for anatomical study. This species can be distinguished from O. gouldiana, O. magna, and O. zediopsis sp. nov. by its small size, decollated, fewer whorls, roundish aperture, more spiral inferior lamella, and equal palatal plicae. This new species is clearly distinct from O. decollata by its spiral inferior lamella visible from aperture, smoother shell, pink color, and more bulging whorls.

Compared to the Vietnamese dextral species, O. duci Maassen & Gittenberger, 2007 exhibits thinner and oblique aperture, sinus higher, obviously emerged subcolumellaris, very fine striations and more ventrally unequal palatal plicae than this species.

Holotype CUMZ 13064 (Fig. 16E). Measurement: shell height 25 mm, shell width 6.5 mm and 10 whorls. Paratypes CUMZ 13065 (50 shells; Fig. 16D, F), NHMUK 20220508 (2 shells) and JG-C 2884 (2 shells).

Weibyan Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (17°13'38.2"N, 97°37'24.0"E).

The specific name zediopsis is a compound word; ‘zedi’ is one of several terms in the Myanmar language that refer to a stupa or pagoda, and the Greek suffix -opsis means ‘having the appearance of or like’. It refers to the Myanmar pagoda-like shell shape of this species.

Shell fusiform, with four to five white apical whorls, and nearly smooth shell surface. Inferior lamella straight ascending or almost flattened, palatal plicae lateral, equally oblique, superior lamella distinct at transition to spiralis, and clausilium plate lateral side and less bent inwards.

Shell fusiform, opaque, and chestnut-brown color; 4–5 apical whorls white and rapidly attenuated. Shell surface smooth to with very thin growth lines; suture impressed and distinct. Whorls 10–11, convex, regularly growing, and attenuated to apex. Aperture obliquely pear-shaped, and basis rounded; peristome slightly protruded, large, relatively thickened and slightly expanded. Superior lamella developed, connected to spiralis and slightly low 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, four or five: first and fourth plicae strongest and longest; remaining plicae parallel and equal length; fifth plica smallest. Clausilium plate lateral side and narrow.

This species is only known from the type locality with plentiful shells collected.

No ethanol preserved specimens were available for anatomical study. Oospira gouldiana can be distinguished from O. zediopsis sp. nov. by its less ventricose shell, denser and stronger striations, more spiral inferior lamella, palatal plicae and clausilium more ventrally positioned, and principalis not visible from the aperture view. Likewise, O. shanensis can be differentiated from this new species by wider spacing between spiralis and inferior lamella, anterior end of inferior lamella reduced at peristome, longer palatal plicae, attached peristome, and clausilium wider and with a hook. Furthermore, O. zediopsis sp. nov. can be differentiated from O. insignis by its more attenuated spire, narrower and more oblique aperture, shorter and more equal palatal plicae.