Chersaecia feddeni ( Blanford, 1865 ) Páll-Gergely, Barna, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 34-36

Chersaecia feddeni ( Blanford, 1865) comb. nov.

Figs 14 F–G, 15C–F

Helix (Plectopylis) feddeni Blanford, 1865: 75–76 , 94 [“Prome”, “Prome, close to the Pagoda”].

Helix (Plectopylis) ponsonbyi Godwin-Austen, 1888: 243 [“Hlindet, Upper Burmah, 1500 feet ”]. Syn. nov.

Helix feddeni – Pfeiffer 1868: 398.

Helix (Plectopylis) feddeni – Godwin-Austen 1875b: 613, pl. 74, fig. 7. — Hanley & Theobald 1875: 52, pl. 131, figs 1–3. — Tryon 1887: 163, pl. 35, figs 84–87. — Tapparone Canefri 1889: 323 (= 47) [“Prome”].

Helix (Plectopylis) fedden (Sic!) – Nevill 1878: 71.

Plectopylis ponsonbyi – Pilsbry 1894: 145, pl. 40, figs 9–12. — Gude 1896b: 178, fig. 22a–e; 1898c: 17, fig. 77a–b.

Plectopylis feddeni – Gude 1897i: 171, fig. 64a–d; 1899c: 75–77, fig. 104a–b.

Plectopylis (Plectopylis) feddeni – Gude 1899d: 148; 1899e: 175; 1914b: 128–129, fig. 63a–f.

Plectopylis (Plectopylis) ponsonbyi – Gude 1899d: 148. — 1899e: 175; 1914b: 119–120, fig. 58a–e.

Diagnosis

A medium-sized, sinistral, flat species with Plectopylis - type palatal plicae, and two lamellae on the parietal wall with a main and a lower plica.

Material examined

Types

MYANMAR: 3 shells, syntypes of feddeni (2 broken, 1 complete shell with D = 16.1 mm), Prome- Pegu ( NHMUK 1906.1.1.730); holotype of P. ponsonbyi (D = 17.8 mm), Burmah, Hlindet ( NHMUK 1913.3.14.9).

Additional material

MYANMAR: 1 shell, Moulmein, coll. Möllendorff (“ ponsonbyi ”) ( SMF 150095); 1 shell (“ feddeni ”), Barma, Prome, coll. Möllendorff ( SMF 150099).

Description

SHELL. Sinistral, whitish, fragile, flat, widely umbilicated; protoconch consists of 2.25–2.5 whorls with shallow suture; protoconch finely granular, after first whorl with rather rough wrinkles, which increase in strength towards end of protoconch; whorls 6.25–6.5, teleoconch whorls separated by a deep suture; dorsal surface with rather irregular, rough, dense ribs; ventral surface with lower ribs; fine spiral striation, weaker than radial lines, also discernible on entire shell; area near suture with some fine periostracal folds; body whorl rounded; aperture strongly oblique to shell axis, rounded; peristome whitish, expanded and reflected; parietal callus as strongly developed as peristome, slightly S-shaped; apertural fold rather strong, free from parietal callus; umbilicus wide, shallow.

Two syntypes of feddeni had been opened; one of them possessed three lamellae which is a teratological condition, therefore not included in the description (see Remarks). The holotype of ponsonbyi had also been opened. Parietal wall with two vertical lamellae; posterior lamella slender, elevated, with posteriorly elongated ends; anterior lamella shorter, more robust, with posteriorly, slightly elongated upper end, whereas both ends are strongly elongated anteriorly (upper one: main plica, lower one: basal plica); apertural fold connected to main plica in the intact syntype of feddeni , and free in the other two syntypes of feddeni and the holotype of ponsonbyi (these are probably subadult shells); lower plica slender, reaches peristome. Palatal plicae six; upper one close to suture, of normal size; second strongly elongated anteriorly; third short, depressed S-shape; fourth and fifth connected and form a vertical plate; sixth curved and of normal length; there can be additional denticles on the posterior ends of the plicae.

MEASUREMENTS (in mm). D = 16.1, H = 5.1 (syntype of feddeni ); D = 17.8, H = 6 (holotype of ponsonbyi ).

Differential diagnosis

Chersaecia feddeni differs from C. magna in the smaller, more fragile shell, stronger sculpture, and the main plica, which is connected to the apertural fold. Chersaecia leucochila has a more elevated spire, domed dorsal side and a narrower umbilicus, and although the known specimens are somewhat weathered, the sculpture of C. leucochila is weaker than that of C. feddeni . See also under C. goniobathmos .

Distribution

Chersaecia feddeni is known from southern Myanmar only.

Remarks

The shell shape of Plectopylis feddeni is identical to that of P. ponsonbyi . The only difference between the types of the two taxa is the short main and lower plicae in the latter. The holotype of P. ponsonbyi seems to be a subadult specimen because it has a relatively thin peristome and parietal callus. Therefore, the shorter plicae that differentiates P. feddeni , from P. ponsonbyi may be the result of ontogenetic variation and not a species-level difference.

Godwin-Austen (1875b) published a drawing of a specimen of Chersaecia feddeni with three lamellae. Gude (1914b) even produced his identification key stating that feddeni has “three transverse parietal plates”. Both other specimens of the same sample had only two lamellae, which is usual in the genus. Consequently, the three lamellae may be the result of a teratological condition of the normal two lamellae with no taxonomic value.

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).