Chersaecia mogokensis, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 44-46

Chersaecia mogokensis sp. nov.

urn:lsid:zoobank.org:act:8E2812E3-52AF-4CF9-A01D-FD01ED8396E7

Figs 20C , 21E–F

Diagnosis

Shell large, flat, widely umbilicated, parietal wall with a single lamella and a short lower plica, palatal plicae oblique, with additional denticles at their posterior ends.

Etymology

The name mogokensis refers to the type locality (Mogok). This name was written on the label of the specimen, but apparently has never been published.

Material examined

Holotype

MYANMAR: 1 shell, holotype (D = 23.6 mm), Burmah, Mogok, ruby mines, coll. Godwin-Austen ( NHMUK 20140787 ).

Description

SHELL. Sinistral, almost completely flat, only protoconch protrudes above dorsal surface; original colour might be reddish-brown; protoconch consists of slightly more than 2.5 whorls, separated by shallow suture; dorsal side of the protoconch irregularly, roughly wrinkled, but ventral side (i.e., inside the umbilicus) clearly tuberculated; whole teleoconch irregularly wrinkled sometimes with spiral lines especially on the apical side; whorls 6.75; teleoconch whorls separated by a deep suture; peristome

Fig. 21. Parietal (A, C, E, G, I, J, L, N, P, R) and palatal (B, D, F, H, K, M, O, Q, S) plication of species of Chersaecia Gude, 1899 . A–B. C. magna (Gude, 1897) comb. nov., holotype (NHMUK 1922.8.29.37). C–D. C. magna (“ P. lissochlamys ”, after Gude 1914b). E–F. C. mogokensis sp. nov., holotype (NHMUK 20140787). G–H. C. nagaensis (Godwin-Austen, 1875) , syntypes (NHMUK 1903.7.1.753). I. C. nagaensis (NHMUK 1874.9.26.3). J–K. C. nagaensis muspratti (Gude, 1897) (after Gude 1914b). L–M. C. perarcta simplex ( Solem, 1966) (after Solem 1966). N–O. C. perarcta perarcta ( Blanford, 1865) (NHMUK 1906.2.2.275). P–Q. C. perarcta perarcta (UF 448575). R–S. C. perarcta perarcta , loc. “ 5.5 km west of Chiang Rai ” (coll. PGB). Arrows below the letters indicate the direction of the aperture. Not to scale.

strongly thickened and slightly reflected; parietal callus strongly developed, sharp, slightly S-shaped; apertural fold very short, denticle-like, free from parietal callus.

Parietal wall with a single, slightly curved lamella and a short lower plica. Palatal wall with six plicae; first and last straight, horizontal; remaining ones oblique, with additional denticles at their posterior ends.

MEASUREMENTS (in mm). D = 23.6, H = 7.7 (holotype).

Differential diagnosis

In size and shape Chersaecia mogokensis sp. nov. resembles species of the genus Plectopylis . However, the straight, oblique palatal plicae, and the single lamella differentiates it from all species of Plectopylis . The most similar species of Chersaecia in outer shell morphology is C. shanensis , which nevertheless has strongly developed lower, main and intermediate plicae, a much stronger apertural fold, and a protoconch lacking or with a few low growth wrinkles. Chersaecia magna is also similar in outer appearance, but possesses two parietal lamellae and a very long apertural fold. All other species of Chersaecia are much smaller and/or have strongly developed main plicae.

Distribution

The only known specimen of Chersaecia mogokensis sp. nov. is from the type locality.

Figures

Fig. 20. Shells of species of Chersaecia Gude, 1899. A. C. magna (Gude, 1897) comb. nov., holotype (NHMUK 1922.8.29.37). B. C. magna, holotype of Plectopylis lissochlamys Gude, 1897 syn. nov. (NHMUK 1922.8.29.38). C. C. mogokensis sp. nov., holotype (NHMUK 20140787). Scale bar = 10 mm. All photos: H. Taylor.