Chersaecia goniobathmos ( Ehrmann, 1922 ) Páll-Gergely, Barna, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 36-37

Chersaecia goniobathmos ( Ehrmann, 1922) comb. nov.

Figs 14 C–E, 15G–H

Plectopylis (Plectopylis) goniobathmos Ehrmann, 1922: 10–12 , figs a–b, unnumbered plate, fig. 3a–c [“Pekon, südliche Shan-Staaten, in ca. 1000 m Höhe”].

Diagnosis

A small to medium-sized, sinistral, brownish species with two lamellae, long main and lower plicae reaching the aperture, and Plectopylis - type palatal plicae.

Material examined

Types

MYANMAR: 1 shell, lectotype (D = 14.7 mm), Süd. Schan-Staaten: Pekor, 1000 m, W. Micholitz leg., coll. Ehrmann ( SMF 150100 a); 1 shell, paralectotype, same data as for preceding ( SMF 150100 b); 1 paralectotype, same data as for preceding ( SMF 150100 c); 2 paralectotypes, same data as preceding ( SMF 150100 d–e).

Description

SHELL. Sinistral, flat or with slightly elevated spire; colour dark to light brown; protoconch very finely tuberculated, tubercles arranged in radial lines; teleoconch with reticulated sculpture; radial lines dominant on dorsal side; on ventral side spiral and radial sculptural elements of comparable strength; whorls 6.25–6.75 (n = 2), separated by rather shallow suture; whorls slightly angled, flat above; peristome reflected and slightly thickened; parietal callus elevated, rather sharp and V-shaped; apertural fold connected to parietal callus.

Two opened shells were examined. Parietal wall with a rather straight posterior lamella having posteriorly elongated lower, and posteriorly as well as anteriorly elongated upper ends, and a shorter, straight anterior lamella with posteriorly elongated upper and lower ends; upper elongation of anterior lamella does not reach posterior lamella; main plica long, reaches apertural fold; intermediate plica short, lower plica very long, starts below posterior lamella and reaches peristome. Palatal plicae similar to that of Plectopylis ; first three plicae horizontal, straight, fourth and fifth form a vertical plate, last plica also straight, horizontal, and strongly elongated anteriorly.

MEASUREMENTS (in mm). D = 14.7–16.4, H = 5.6–6.2 (lectotype and syntypes, n = 3).

Differential diagnosis

Shell shape Chersaecia goniobathmos is generally similar to C. leiophis (especially the pseudophis -like shells). There are, however, considerable differences in the plication, namely (1) Chersaecia leiophis has only a single lamella (the anterior one is missing), whereas C. goniobathmos has two; (2) Chersaecia goniobathmos has a very long lower parietal plica, which is short in C. leiophis ; (3) the palatal plicae of C. goniobathmos are typical of that of the genus Plectopylis , but in the case of C. leiophis the fourth and fifth plicae do not form a vertical plate, but are oblique. Chersaecia goniobathmos differs from C. feddeni in the more elevated spire, the apertural fold, which is connected to the parietal callus, and the main plica, which is connected to the apertural fold.

Distribution

Chersaecia goniobathmos is known from the type locality only.

Figures

Fig. 14. Shells and protoconchs of species of Chersaecia Gude, 1899. A–B. C. auffenbergi sp. nov., holotype (UF 345566). C. C. goniobathmos (Ehrmann, 1922) comb. nov., lectotype (SMF 150100a). D–E. C. goniobathmos, paralectotype (SMF 150100c). F. C. feddeni (Blanford, 1865) comb. nov., syntype (NHMUK 1906.1.1.730). G. C. feddeni, holotype of P. ponsonbyi (Godwin-Austen, 1888) syn. nov. (NHMUK 1913.3.14.9). Scale bars: A, C–D, F–G = 10 mm; B, E = 1 mm. Photos: T. Deli (A), B. Páll-Gergely (B–E), H. Taylor (F–G).