Chersaecia shanensis ( Stoliczka, 1873 )

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 62-65

Chersaecia shanensis ( Stoliczka, 1873)

Figs 5 A–B, 24E–H, 26D–F, 28, 29A–B

Plectopylis shanensis Stoliczka, 1873: 170 . [“Provinciam Burmanam ‘Shan-states’ dictam”].

Helix (Plectopylis) trilamellaris Godwin-Austen, 1875a: 43–44 [“Burmah”, exact locality unknown].

Helix (Plectopylis) shanensis – Hanley & Theobald 1876: 59, pl. 149, figs 8–9. — Tryon 1887: 162–163,

pl. 36, figs 10–11 (with trilamellaris as a synonym). Helix (Plectopylis) shawensis [sic] – Nevill 1878: 71. Helix (Plectopylis) trilamellaris – Nevill 1878: 71 (synonym of shawensis [sic]). — Godwin-Austen

1879a: 2 (synonym of shanensis ). Plectopylis shanensis – Gude 1897g: 36, fig. 48a–c; 1899c: 77, fig. 105. Plectopylis (Chersaecia) shanensis – Gude 1899d: 148; 1899e: 175; 1914b: 111–112, fig. 53a–d; 1920:

62–63. Chersaecia shanensis – Páll-Gergely et al. 2015c: 10.

Diagnosis

A sinistral, medium-sized, brownish-corneous species with long main and lower plicae on the parietal wall; main plica connected to apertural fold; intermediate plica long, usually visible from aperture; palatal plicae parallel and straight, sometimes divided.

Type material

According to Godwin-Austen (1879 a), the collection of Stoliczka was deposited in the Indian Museum (currently the Zoological Survey of India). ZSI does not loan specimens, and my request for images was not successful. Therefore, I have not examined the types of Chersaecia shanensis . According to Godwin- Austen (1879a), G. Nevill compared Plectopylis trilamellaris Godwin-Austen, 1875 to Stoliczka’s type specimens of P. shanensis , and he confirmed their identity. According to the original description of P. trilamellaris , two specimens (syntypes) are present in the collection of the Indian Museum, Calcutta.

Material examined

MYANMAR: 1 shell, Shan States ( NHMUK 1906.1.1.736); 2 shells, Shan States ( NHMUK 1888.12.4.1551–1552); 5 shells, Mandalay, near Yinmabin Vill., loc. 20091018A, 20°49.540′ N, 96°24.830′ E, 289 m a.s.l., 18 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Ohara); 2 shells, Shan, Kalaw, Shwe U Min Cave, loc. 20091018B, 20°37.256′ N, 96°33.443′ E, 1340 m a.s.l., 18 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Ohara); 2 shells, same data as for preceding (coll. PGB, ex coll. K. Okubo); 1 shell ( Fig. 26D ), same data as for preceding ( NHMUK 20170293); 1 specimen (preserved in ethanol with corresponding shell), same data as for preceding ( NHMUK 20170150, ex coll. J.U. Otani); 2 shells, Shan, in the suburbs of Kalaw, Myin Mahti Cave, loc. 20091018C, 20°35.417′ N, 96°36.720′ E, 1320 m a.s.l., 18 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Ohara); 2 shells, same data as for preceding (coll. PGB, ex coll. K. Okubo); 1 shell ( Fig. 26E ), same data as for preceding ( NHMUK 20170292); 1 shell + ethanol-preserved body, same data as for preceding ( NHMUK 20170151, ex coll. J.U. Otani).

INDIA: 2 shells, Simla Hills, Pinagu, 8300–8700 ft a.s.l., Annandale, V.17 ( NHMUK).

Description

SHELL. Sinistral, glossy, brownish-corneous or reddish, flat, only protoconch protruding above dorsal surface; protoconch consists of 2.5–3 whorls; finely granulated on both dorsal and ventral surfaces; teleoconch finely, irregularly wrinkled; entire shell consists of 6.5–7 whorls; aperture oval; peristome white, reflected and slightly thickened; parietal callus elevated, sharp and V-shaped; apertural fold strong, connected to parietal callus; umbilicus very wide and moderately deep.

Four shells belonging to two populations were opened. Parietal wall with a single, short lamella having posteriorly slightly elongated upper and lower ends; intermediate plica attached to lamella, variable in length (up to the length of lamella; in that case visible in oblique view through the aperture); in some shells (subadults?), intermediate plica free from lamella; main and lower plicae not connected to lamella and run until peristome. Palatal wall with usually seven horizontal, straight plicae; first short and runs parallel with the suture; second is longest; remaining ones of equal length; additional, denticle-like plicae visible at posterior ends of seven horizontal plicae (usually more than one denticle belongs to one plica).

MEASUREMENTS (in mm). D = 19.1–20.1, H = 6.9–7.4 (20091018 B, n = 2); D = 14.4–15.5, H = 5–5.4 (20091018 C, n = 2).

CHARACTERS OF THE GENITAL STRUCTURE. Two specimens were anatomically examined. ‘Specimen 1’ had no embryos in its uterus (loc. 20091018 B, NHMUK 20170150); ‘Specimen 2’ had approximately seven embryos in its uterus (loc. 20091018 C, NHMUK 20170151).

Left ommatophoral retractor runs between penis and vagina; penis very long, cylindrical, internally with approximately 10 irregular, interrupted longitudinal folds, forming a rather squamous (scaly) surface; epiphallus slightly shorter than penis, although boundary between epiphallus and vas deferens not clearly visible; inner wall of epiphallus with fine tubercles; epiphallus slightly wavy, especially near its insertion to penis; retractor muscle extremely long, inserts on penial caecum; penial caecum very short; vas deferens slender, cylindrical, runs along vagina and gradually increases in diameter towards its insertion to spermoviduct; vagina extremely long, internally with parallel, converging, serrate folds; bursa copulatrix longer than diverticulum, with a slightly thickened bursa; an elongate-ovoid, fragile spermatophore was found in the bursa of one of the specimens; diverticulum relatively long, almost equally thin towards its end, internally with regular, parallel folds.

RADULA. Centrals with small, triangular cusps; endocones of laterals rhomboid; ectocones of first laterals much larger than centrals; ectocones of marginals undivided, endocones of marginals undivided or divided by shallow incision.

Differential diagnosis

The large, reddish-brownish shell, the single lamella, the lower and main plica which run until the peristome, the long intermediate plica and the horizontal palatal plicae are characteristic of this species and allow separation from all congeners. See also under C. mogokensis sp. nov.

Distribution

Three precise localities are known for this species on the border of Mandalay and Shan Provinces, Myanmar (see also Fig. 12 ). I regard the specimen recorded from India as an erroneous label transcription.

Remarks

The species is very variable in its shell characters. The population from the Shwe U Min Cave is identical with the specimens in the NHM. The shells from the other two localities are much smaller and usually have shorter middle parietal plicae. Some specimens from Yinmabin Village have only straight palatal plicae without small plicae posteriorly.

Figures

Fig. 5. Photos (A, C, E) and schematic drawings (B, D, F) of parietal plicae and lamellae of Plectopylinae Möllendorff, 1898. A–B. Chersaecia shanensis (Stoliczka, 1873), loc. 20091018C (PGB, ex coll. Ohara). C–D. Chersaecia perrierae (Gude, 1898), loc. 20091019A (PGB). E–F. Chersaecia magna (Gude, 1897) comb. nov., holotype (NHMUK 1922.8.29.37). Posterior lamella indicated with red colour, anterior lamella and homologous structures indicated with blue. Not to scale. Photos: B. Páll-Gergely (A, C) and H. Taylor (E).

Fig. 26. Shells of species of Chersaecia Gude, 1899. A. C. scabra sp. nov., holotype (UF 380244). B. Aperture of C. scabra sp. nov., paratype (NHMUK 20170149). C. Protoconch of C. scabra sp. nov (UF 380244). D. C. shanensis (Stoliczka, 1873) (NHMUK 20170293). E. C. shanensis (NHMUK 20170292). F. Protoconch of C. shanensis, loc. 20091018B (coll. PGB). Scale bar (bottom left): A, D–E = 10 mm; B not to scale. Images: T. Deli (A, D–E), B. Páll-Gergely (B–C, F).

Fig. 12. Distribution of plectopylid species in Thailand, Laos and Myanmar. Legends: circle = Chersaecia shanensis (Stoliczka, 1873); filled square = Chersaecia reversalis sp. nov.; empty square = Chersaecia dextrorsa (Benson, 1860); empty rhomb = Hunyadiscus tigrina sp. nov.; filled rhomb = Hunyadiscus saurini Páll-Gergely, 2016; triangle, top up = Plectopylis crassilabris sp. nov.; triangle, top down = Naggsia laomontana (L. Pfeiffer, 1862); empty triangle, top down = Plectopylis bensoni Gude, 1914.