Chersaecia scabra, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 58-61

Chersaecia scabra sp. nov.

urn:lsid:zoobank.org:act:B6A4AF8F-9A14-4CA1-AE9D-BDF4F8A8F77A

Figs 16 E–F, 24O–P, 26A–C, 27

Diagnosis

A small, sinistral, nearly-flat species with a weak apertural fold; parietal wall with two lamellae, and two equal horizontal plicae (main and intermediate) attached to anterior lamella.

Etymology

The specific epithet refers to the fact that even the live collected specimens had an eroded shell surface (scaber / scabra : erroded in Latin).

Material examined

Holotype

THAILAND: 1 shell (D = 14 mm), Chiang Rae Province , 12 km S, 5 km W of Mae Sai, ravine in limestone mountains, 20°21′13″ N, 99°50′46″ E, 550 m a.s.l., 9 May 1988, F.G. Thompson leg. ( UF 380244).

Paratypes

THAILAND: 3 shells, same data as for holotype ( UF 448576); 1 shell, same data as for holotype ( HNHM 97460); 1 shell, Chiang Rae Province, Tham Tumluang (cave), 7 km S, 2 km W of Mae Sai, 20°22′10″ N, 99°51′28″ E, 470 m a.s.l., 8 May 1988, F.G. Thompson leg. ( UF 347154); 2 shells, Chiang Rae Province, Doi Thung Mountain, 20°20′32″ N, 99°50′21″ E, 1320 m a.s.l., 8 May 1988, F.G. Thompson leg. ( UF 347122); 50 specimens (preserved in ethanol: PL053–PL054 used for molecular study), Chiang Rai Province, Doi Tung, 50 m from Wat Phra That Doi Tung, 20°19.540′ N, 99°49.987′ E, 1350 m a.s.l., 30 Mar. 2016, A. Hunyadi leg. (coll. HA); 1 paratype (anatomically examined: PL052 used for molecular study), same data as for preceding ( NHMUK 20170149); 1 shell, Chiang Rai Province, Wat Phra That Doi Tung, 22 Oct. 2016, K. Okubo leg (coll. PGB); 3 shells, same data as for preceding (coll. OKA).

Additional material

THAILAND: 2 juv. specimens (preserved in ethanol), Chiang Rai Province, Doi Tung, 50 m from Wat Phra That Doi Tung, 20°19.540′ N, 99°49.987′ E, 1350 m a.s.l., 30 Mar. 2016, A. Hunyadi leg. (coll. HA).

Description

SHELL. Sinistral, light brown (although all shells, including live collected ones, were weathered), almost flat, only protoconch protrudes above dorsal surface; protoconch consists of 2.5–2.75 whorls, with fine granular structure and inconspicuous wrinkles; teleoconch with dense ribs and spiral sculpture, resulting in a reticulated structure; whorls 6–6.5, separated by a rather shallow suture; aperture rounded; peristome only slightly thickened and reflected; parietal callus low, apertural fold very weak, free from parietal callus.

Three shells were opened. Parietal wall with two vertical lamellae, posterior one longer and C-shaped, with the arms of the ‘C’ pointing posteriorly; anterior lamella short and connected at both ends to horizontal plicae; main and intermediate plicae of comparable length; ends of plicae visible through oblique view into aperture; main plica and apertural fold situated far from each other. Palatal wall with six plicae; first straight and parallel with upper suture; second short and curved; third longest; fourth and fifth vertical and fused to each other, forming an inverted structure similar to the letter Y; last plica short and curved downwards.

MEASUREMENTS (in mm). D = 11.2–13, H = 3.7–4.5 (n = 5).

CHARACTERS OF THE GENITAL SYSTEM. A single specimen was dissected (NHMUK 20170149). Right ommatophoral retractor runs between penis and vagina-vas-deferens; penis reduced, very short, blunt, ovoid, inner wall with a strongly thickened fold; retractor muscle short, inserts on proximal end of penis; vas deferens extremely long, thick proximally, slowly reduces in diameter towards penis, internally with oblique, converging longitudinal folds; vagina slender near atrium, slowly increases in width towards spermoviduct; interior of vagina with reticulated sculpture proximally, distal part of vagina with parallel longitudinal folds; diverticulum slender and relatively short, bursa copulatrix long and slender, both originate near base of spermoviduct; diverticulum internally with elevated, parallel, regular folds.

RADULA. Centrals with small, triangular cusps with pointed tips; endocones of laterals subrhomboid with pointed tip; ectocones of first laterals larger than centrals; ectocones of marginals undivided or divided to two; endocones of marginals triangular, undivided or divided by shallow incision.

Differential diagnosis

Chersaecia scabra sp. nov. largely resembles C. woodthorpei in the arrangement of the palatal and parietal plicae and lamellae, but the main plica of the latter species reaches the parietal callus, the intermediate plica is shorter, and a very long lower plica reaches the parietal callus. Moreover, C. scabra sp. nov. is larger, has less shouldered whorls and lacks the series of horizontal palatal plicae, which are characteristic in C. woodthorpei .

Chersaecia auffenbergi sp. nov. also has a similar parietal lamellation, but that species is much flatter and has Y-shaped palatal plicae.

Distribution

The new species is known from four geographically-proximate sites situated within 6 km of each other in northern Chiang Rae Province, north Thailand ( Fig. 17 ).

Figures

Fig. 16. Radula of species of Chersaecia Gude, 1899. A, C, E. Central and first lateral teeth. B, D, F. Marginal teeth. A–B. C. auffenbergi sp. nov. (NHMW MO-112 221) C–D. C. perrierae (Gude, 1898) (NHMUK 20170148). E–F. C. scabra sp. nov. (NHMUK 20170149). All images: B. Páll-Gergely.

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.