Chersaecia leiophis ( Benson, 1860 )

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 37-41

Chersaecia leiophis ( Benson, 1860)

Figs 15 I–Q, 18, 19A–B

Helix (Plectopylis) leiophis Benson, 1860: 244 , 246 [“ad Kwadouk, prope Thyet Mio”].

Helix (Plectopylis) pseudophis Godwin-Austen, 1875b: 610–613 , pl. 74, fig. 3.

Plectopylis (Chersaecia) kengtungensis Gude, 1914a: 53 , figs a–c (+ unnumbered figures) [“E. Burma: Kengtung”]. Syn. nov.

Plectopylis (Chersaecia) degerbolae Solem, 1966: 95–97 , fig. 23a–b., pl. 2 figs F–H [“Doi Sutep, North Thailand at 1,000 meters elevation (number 1173)”]. Syn. nov.

Helix (Plectopylis) leiophis – Blanford 1865: 94 [“Thyet Myo”, “Akoutoung”]. — Hanley & Theobald 1870: 7, pl. 13, fig. 8. — Godwin-Austen 1875a: 44 (as a synonym of refuga ); 1875b: 613, pl. 74, fig. 2. — Tryon 1887: 163, pl. 35, figs 88–89.

Helix leiophis – Pfeiffer 1868: 396.

Plectopylis pseudophis – Godwin-Austen 1875a: 44 [“Thayatmyo, in Pegu ”]. — Gude 1897i: 170, fig. 62a–c; 1899b: 17, fig. 77a–g; 1908: 88–89 (synonym of leiophis ).

Helix (Plectopylis) pseudophis – Tryon 1887: 162, pl. 35, figs 80–81.

Plectopylis leiophis – Gude 1898c: 16, fig. 76a–c; 1908: 88–89.

Plectopylis (Chersaecia) pseudophis – Gude 1899d: 148; 1899e: 175.

Plectopylis (Chersaecia) leiophis – Gude 1899d: 148; 1899e: 175; 1914b: 99–102, figs 44–46. — Zilch 1960: 595, fig. 2093.

Plectopylis (Chersaecia) kengtungensis – Gude 1914b: 97–98, fig. 43a–c + unnumbered figs.

Chersaecia leiophis – Páll-Gergely et al. 2015c: 10.

Chersaecia kengtungensis – Páll-Gergely et al. 2015c: 10.

Chersaecia degerbolae – Páll-Gergely et al. 2015c: 10.

Diagnosis

A small to medium-sized, sinistral species with a single lamella and a main plica on the parietal wall, and parallel plicae on the palatal wall.

Material examined

Types MYANMAR: 3 shells, syntypes of kengtungensis (D = 11.4–11.8 mm), Burmah, Shan States ( NHMUK 1903.7.1.750); 4 shells, probably syntypes of pseudophis, Burmah , coll. Godwin-Austen ( NHMUK 1903.7.1.754).

THAILAND: 1 shell, holotype of P. degerbolae (preserved in ethanol: PL123 used for molecular study) (D = 16.2), N. Thailand, Doi Sutep, O.H., 1000 m a.s.l., 1 Jul. 1960, Degerbøl leg. (nr. 1173) ( ZMUCGAS- 485).

Additional material

LOCALITY UNKNOWN: 1 shell ( “ refuga ”), ex-exhibition coll. “alte Schau-Slg.” ( SMF 150116); 1 shell, ex-exhibition coll. “alte Schau-Slg.” ( SMF 150114); 67 shells, coll. Blanford ( NHMUK); 3 shells, coll. Blanford ( NHMUK); 1 shell, “from author” ( NHMUK 1888.12.4.1532).

MYANMAR: 1 shell, Pegu, ( NHMS 122178); 3 shells, Barma, coll. Möllendorff (photographed for Zilch 1960) ( SMF 150115); 1 shell, Brit. Indien, coll. Bosch ex Rolle (Schlüter) ( SMF 172055); 3 shells, Akouktoung ( NHMUK 1888.12.4.1526–1528); 2 shells (mixed sample with C. refuga ) ( NHMUK 20170160); 1 shell, Burma, ex Museum Cuming ( NHMUK 20150360); 1 shell (mixed sample with C. refuga ) ( NHMUK 20170162); 1 shell, India, Thyet Myo ( NHMUK 20170161); 3 shells, Burmah (donated by Prof. Kenneth D. Thomas), 16 Oct. 2012 ( NHMUK); 3 shells, Prome(?) ( NHMUK /13); 1 shell, Ava(?) ( NHMUK); 4 shells, Arakan Coast, Nioung jo ( NHMUK 1888.12.4.1544–1547); 1 shell, Pegu, Lower Burma, coll. Salisbury ex Beddome ( NHMUK); 3 shells, India, Burmah, ( NHMUK 1871.9.23.205); 6 shells, Burmah ( NHMUK); 3 shells, Burmah, coll. Kennard ex Leipner ex Bullen ( NHMUK); 5 shells, Akouktoung ( NHMUK); 5 shells, Pegu, Thayet Myo?, coll. Blanford ( NHMUK 1906.1.1.742); 3 shells, Upper Irawadi ( NHMUK 1888.12.04.1533–1535); ± 15 shells, Prome, coll. Blanford ( NHMUK) .

THAILAND: 1 shell ( Fig. 19B ), Chiang Mae Province, NW side of Doi Pha Sam Sao, 19°24′27″ N, 99°2′56″ E, 20 May 1988, F.G. Thompson leg. ( UF 346988); 3 shells, same data as for preceding ( UF 448573); 1 shell, same data as for preceding ( HNHM 97456); 1 shell, Chiang Mae Province, Doi Pha San Sao Mountain, 1 km W of Ban Prang Ma-o, 19°25′58.26″ N, 99°4′14.02″ E, 500 m a.s.l., 19 Jun. 1987, F.G. Thompson leg. ( UF 346677); 1 shell, Chiang Mai Province, Ban Pang Mao, 1.1 km NW of Wat Suwan Khiri, 19°25.981′ N, 99°04.335′ E, 510 m a.s.l., 8 Feb. 2015, A. Hunyadi leg. (coll. HA).

Description of typical leiophis

SHELL. Sinistral, flat above or with very slightly elevated spire; colour light brown to yellowish and white; protoconch consists of 2.5–2.75 whorls, very finely tuberculated, with fine wrinkles over the entire surface; teleoconch with reticular structure, only periphery of body whorl dominated by radial riblets, rest of shell surface sculptured with spiral and radial elements of ca equal strength; whorls 5.75–6.25 (n = 3), separated by rather shallow suture; whorls angled, flat above; peristome expanded and slightly thickened; parietal callus elevated, rather sharp and V-shaped; apertural fold connected to parietal callus.

Three opened shells of typical leiophis were examined. Parietal wall with a single curved lamella; main plica long, reaches apertural fold; lower plica short, situated under lamella; intermediate plica short; all horizontal parietal plicae free from lamella or connected to it. Palatal plicae six or seven; first and last plicae straight, middle ones straight, horizontal or oblique, or sometimes fourth and fifth vertical; sometimes the plicae have a posterior denticle.

MEASUREMENTS (in mm). D = 14.55–15.3, H = 6.1–6.9 (n = 3, NHMUK 1888.12.4.1526–28, typical leiophis ); D = 16.2, H = 6.2 (holotype of degerbolae , ZMUC-GAS-485); D = 13.6–15.6, H = 5.5–5.9 (Thai specimens, n = 3).

Differential diagnosis

Chersaecia perarcta is smaller and flatter, usually with concave surface. See under C. nagaensis and C. refuga .

Distribution

Chersaecia leiophis is known from Myanmar (states of Bago, Pyay, Thayet, Shan, etc.) and northern Thailand (see Fig. 17 for localities in Thailand).

Remarks

The relationship between Plectopylis pseudophis and P. leiophis was discussed by Gude (1908). According to him, the typical forms differ in the following characters: toothed outline of the lamella, elevated spire, and the absence of a short additional plica between the main and intermediate plicae in pseudophis ; smooth lamella, flat spire and the presence of an additional plica between the main and intermediate plicae in leiophis . Based on the specimens examined by Gude (1908), all these characters are variable across populations and do not allow for the separation of these two species. Therefore, Plectopylis pseudophis was assigned as a synonym of P. leiophis . I confirmed Gude’s observations by examining the same specimens, and agree with his conclusion.

Plectopylis kengtungensis was compared with P. nagaensis and P. muspratti in the original description, but not with P. leiophis ( Gude 1914a) . According to the original description of P. kengtungensis , it has the palatal plicae united with a “low transverse ridge”, whereas this was not mentioned in the case of P. leiophis . This character, however, varies considerably between specimens within the same populations, probably depending on their age. Older shells tend to have stronger calcareous layers built on both the parietal and palatal sides of the armature. Regardless of the ridge, the morphology of palatal plicae of typical kengtungensis and leiophis are similar (usually long plicae with small denticles posteriorly, and the 5 th plica is oblique). The plication of the parietal side is also similar in the two forms. The shell shape of typical leiophis is quite flat, whereas the spire of P. kengtungensis is slightly elevated. This character also does not differentiate the two species, because typical pseudophis (= synonym of leiophis ) shells have similar shell shape to that of P. kengtungensis . Because of the above-mentioned information, I assign P. kengtungensis as a synonym of P. leiophis .

Plectopylis (Chersaecia) degerbolae does not differ in shape from typical P. leiophis specimens. Solem (1966) mentioned the following differences: (1) both horizontal plicae are free from the lamella in degerbolae , and at least one of them is fused to the lamella as in leiophis ; (2) the denticles posterior to the palatal plicae are absent in degerbolae and present in leiophis ; (3) the larger shell size of degerbolae . The first is not true, because the lamella and the horizontal plicae are separate in some leiophis samples, for example in typical ones (NHMUK 1906.02.02.145). The second might be true (in some leiophis samples only 1–2 additional denticles found), although this character appears too variable to be useful. The same prudence should be applied with regard to the slight differences in shell size. Therefore, I treat P. degerbolae as a synonym of Chersaecia leiophis .

The shells collected in Thailand on the Doi Pha San Sao Mountain differ from typical C. leiophis by the strongly descending aperture and the strongly expanded and reflected peristome. This form may deserve subspecific differentiation.

According to the original descriptions of P. degerbolae and P. simplex , their protoconchs have “irregular growth wrinkles” and are “smooth”, respectively ( Solem 1966). I examined type specimens of both species and found that both have finely tuberculated protoconchs, which is a characteristic trait of the genus. In addition to the tubercles, the second whorl of the protoconch is irregularly wrinkled in the paratype of P. degerbolae , but no wrinkles were found on the protoconch of the paratype of P. simplex .

Figures

Fig. 15. Parietal (A, C, E, G, I, K, L, N, P, R) and palatal (B, D, F, H, J, M, O, Q, S) plication of species of Chersaecia Gude, 1899. A–B. C. auffenbergi sp. nov. (UF 448572). C–D. C. feddeni (Blanford, 1865) comb. nov. (after Gude 1914b). E–F. C. feddeni (“Plectopylis ponsonbyi”, after Gude 1896b). G–H. C. goniobathmos (Ehrmann, 1922) comb. nov. (SMF 150100c). I–J. C. leiophis (Benson, 1860) (NHMUK 1902.02.02.145). K. C. leiophis (“pseudophis”, after Gude 1914b). L–M. C. leiophis (“kengtungensis”, after Gude 1914b). N–O. C. leiophis (UF 446988). P–Q. C. leiophis, holotype of Plectopylis degerbolae Solem, 1966 (ZMUC-GAS-485). R–S. C. leucochila (Gude, 1897) comb. nov. (NHMUK 1922.8.29.39). Arrows below the letters indicate the direction of the aperture. Not to scale.

Fig. 19. Shells of species of Chersaecia Gude, 1899. A. C. leiophis (Benson, 1860), holotype of P. degerbolae Solem, 1966 (ZMUC-GAS-485). B. C. leiophis from Thailand (UF 346988). C. C. leucochila (Gude, 1897) comb. nov., holotype (NHMUK 1922.8.29.39). Scale bar = 10 mm. Photos: B. Páll-Gergely (A), T. Deli (B), H. Taylor (C).

Fig. 17. Distribution of plectopylid species in Northern Thailand. Legends: circle = Chersaecia auffenbergi sp. nov.; triangle = Chersaecia leiophis (Benson, 1860) (empty triangle shows the type locality of Plectopylis degerbolae Solem, 1966); empty square = Chersaecia perarcta simplex (Solem, 1966); cross = Chersaecia perarcta perarcta (Blanford, 1865); filled square = Chersaecia scabra sp. nov.; rhomb = Chersaecia densegyrata sp. nov.; the upper filled triangle also shows the locality of Naggsia oligogyra sp. nov.