Plectopylis malayana, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 97-102

Plectopylis malayana sp. nov.

urn:lsid:zoobank.org:act:987C6622-4318-4E5E-AE9C-097C21DC546F

Figs 35 L–M, 44A–E, 45, 46A–B

Plectopylis revoluta – van Benthem Jutting 1960: 17 [“Limestone hill Kaki Bukit, near kampong Wang Tangga, Perlis ”]. — Berry 1963: 13, fig. 51 [“abundant in limestone hills in North Malaya”]. — Maassen 2001: 78.

Diagnosis

A medium-sized, sinistral, brown-shelled species having periostracal filaments along the upper keel of the body whorl; apertural fold not in contact with parietal callus; lambda-complex with a short connecting plica anteriorly.

Etymology

The species is named for Malaysia, where most of the samples were collected.

Material examined

Holotype

MALAYSIA: 1 shell (D = 18.1 mm), Perlis, Kaki Bukit (N of Kangar), Oct. 1998, J. and Ch. Hemmen leg. ( HNHM 97469 ).

Paratypes

MALAYSIA: 11 shells, same data as for holotype (coll. JG); 9 shells, same data as for holotype (coll. PGB); 20 shells, same data as for holotype (coll. HE); 2 shells, same data as for holotype ( NHMW 108117); 5 shells, Perlis, Bukit Kubu (NE of Kuala Perlis), 21 Mar. 1998, J. and Ch. Hemmen leg. (coll. JG); 4 shells, same data as for preceding (coll. PGB); 1 shell, Perlis, Wangga Tangga Valley, near Kaki Bukit, 23 Mar. 1998, J. and Ch. Hemmen leg. (coll. HA); 10 shells, same data as for preceding (coll. JG); 9 shells, same data as for preceding (coll. PGB); 3 shells, Nha-Krabi, south, Apr. 2003, Dieter Hörner leg. (coll. JG); 1 shell, Perlis, about 21 km N of Kangar, max. 3 km from the Thai border, Kaki Bukit, near Kampung Wang Tangga, 6°38′28″ N, 100°12′08″ E, in leaf litter in a secondary forest, base of limestone hill, 17 Mar.1995, V. Kessner leg. (coll. PGB); 3 shells, same data as for preceding (coll. REI); 2 shells, Perlis, Titi Tinggi Mukim, Kaki Bukit, Gua Kelam, towards Wang Tangga, near fossil locality site, live/dead collected among disturbed limestone rocks and litters near exit of cave, 26 Apr. 1996, Chan Sow-Yan and Leo Nguang leg., ex Chan 1997 ( SMF 311305); 35 shells, Perlis, Kaki Bukit, Gua Kelam, 06°38.68′ N, 100°12.23′ E, 9 Jul. 1999, W. Maassen leg. (coll. WM); 4 shells (preserved in ethanol: PL009, PL010, PL019, PL020 used for molecular study), Perlis, Kaki Bukit, around Gua Kelam, 06°38′ N, 100°11′ E, 50 m a.s.l., 11 Jan. 2013, A. Hunyadi leg. (coll. HA); 1 paratype (preserved in ethanol, anatomically examined), same data as for preceding ( NHMUK 20170153); 44 shells, West Malaysia, Perlis, Wang Kelian State Park near Thai Border, 06°41.98′ N, 100°11.80′ E, 10 Jul. 1999, W. Maassen leg. (coll. WM); 10 shells, West Malaysia, Perlis, limestone hill, 30 km N of Kangar, 06°41.00′ N, 100°11.21′ E, 10 Jul. 1999, W. Maassen leg. (coll. WM); 5 shells, West Malaysia, Perlis, Bukit Air Park, N of Kangar, 11 Jul. 1999, W. Maassen leg. (coll. WM); 4 shells, West Malaysia, Perlis, Kaki Bukit, near Kampung Wang Tangga, 11 Jul. 1995, V. Kessner leg. (coll. WM); 1 shell, Perlis, Kaki Bukit, near Kampung Wang Tangga, in leaf litter, secondary forest at the base of limestone hill, 17 Mar. 1995, V. Kessner leg. ( HNHM 42264); 2 shells, Perlis, Kaki Bukit, Kampunk, Wang Tangga, coll. L. Drimmer ( MMGY 69644); 1 shell, Perlis, Kampung Tebing Tinggi, 3.5 km W of Kangar, 06°26.707′ N, 100°09.1931′ E, 20 m a.s.l., 12 Jan. 2013, A. Hunyadi leg. (coll. HA); 46 shells, Perlis, Kaki Bukit, around Gua Kelam, loc. 2013/14, 06°38.674′ N, 100°12.170′ E, 45–55 m a.s.l., 13 Jan. 2013, A. Hunyadi leg. (coll. HA).

THAILAND: 3 shells, Satun Province, Ban Rae, coll. Brandt, 1966 ( MNHN); 4 shells, Satun Province, Ban Rae, 4 Jan. 1966, Brandt leg. ( ZMH 45914); 3 shells, same data as for preceding ( SMF 207667); 2 shells, same data as for preceding except coll. Klemm (nr. 54168) ( NHMW 108223); 3 shells, same data as for preceding except coll. Oberwimmer ( NHMW 108224); 4 shells, same data as for preceding except coll. Biggs ( NHMUK 20170159); 3 shells, same data as for preceding except coll. Brand 1966 ( MNHN IM- 2012-2519); 1 paratype (preserved in ethanol), Satun Province, Thale Ban Nat. Park, lowland rain forest, 6°42′ N, 100°10′ E, ca 400 m, 20 Oct. 1991, M. Andersen, O. Martin and N. Scharff leg. (ZMUC-GAS-1834).

Additional material

MALAYSIA: 1 juv. shell, Perlis, about 21 km N of Kangar, max. 3 km from the Thai border, Kaki Bukit near Kampung Wang Tangga, 6°38′28″ N, 100°12′08″ E, in leaf litter in a secondary forest, base of limestone hill, 17 Mar.1995, V. Kessner leg. (coll. PGB).

Description

SHELL. Sinistral, chocolate brown (or yellowish, if weathered), nearly flat, strongly depressed conical or flat with protoconch slightly protruding above dorsal surface; protoconch consists of 3.25–3.5 whorls, very finely granular, with inconspicuous growth lines on last 1.5–2 whorls; ventral surface of protoconch roughly ribbed; teleoconch with a reticulated surface consisting of very fine, dense ribs and widely-spaced spiral lines; periostracum of fresh specimens with deciduous folds on upper keel of body whorl; whorls 6–6.5, separated by a relatively shallow suture; aperture rounded; peristome thickened and expanded; parietal callus sharp; apertural fold usually short, white and never in contact with parietal callus.

Four shells were opened. Lambda-complex compete; left leg and upper branch relatively short; middle portion of right leg with a short horizontal, attached plica, which is rarely in contact with main plica; short lower plica situated below lambda-complex; in some specimens main plica connected to apertural fold, whereas in others they are free (this trait is probably age-dependent). Palatal wall with six plicae; first three straight with sinuate (S-shaped) posterior ends; last plica slightly curved with its convex side pointing upwards; additional short plica visible above posterior end of last plica; fourth and fifth plicae vertical and fused together, forming a single, vertical plate, which is usually bifurcated below and possesses 1–2 additional horizontal plicae posteriorly.

MEASUREMENTS (in mm). D = 17.6–19.0, H = 6.6–7.2 (n = 4).

CHARACTERS OF THE GENITAL SYSTEM. One specimen was examined. Locality information: Malaysia, Perlis, Kaki Bukit, around Gua Kelam, 06°38′ N, 100°11′ E, 50 m a.s.l., A. Hunyadi leg., 11 Jan. 2013 (NHMUK 20170153). Left ommatophoral retractor runs between penis and vagina; penis relatively long and slender, internally with parallel, serrate folds; epiphallus and vas deferens attached to penis with weak muscle fibres; no penial caecum observed; retractor muscle thick and short, inserts on proximal part of penis; vagina approx. as long as penis, but thicker; bursa copulatrix with a very long, slender stalk, bursa elongate ovoid; diverticulum short, blunt, ovoid; four developing embryos were found in uterus, the most distal one was the most well-developed, with a shell of 3 whorls.

RADULA. Centrals with small, triangular cusps; endocones of laterals rhomboid; ectocones of first laterals larger than centrals; ectocones of marginals undivided, endocones of marginals mostly undivided, or divided by shallow incision.

Differential diagnosis

Plectopylis malayana sp. nov. differs from P. cairnsi by its darker shell, thinner lip, less rounded body whorl, several additional plicae on the palatal wall, shorter left leg, and shorter upper branch of the lambda-complex. Furthermore, the lambda-complex of P. cairnsi is never fused to the main plica (sometimes fused in P. malayana sp. nov.), and P. malayana sp. nov. has a small fold that is attached to the central part of the right leg. Plectopylis bensoni is usually larger than P. malayana sp. nov. and has a rounded body whorl, whereas the body whorl of P. malayana sp. nov. is angled. Moreover, P. malayana sp. nov. has a finely reticulated shell surface, which is nearly smooth in P. bensoni with irregular growth lines.

Distribution

Plectopylis malayana sp. nov. is known from Perlis Province (near the Thai border) in northern Malaysia and the Satun Province in southern Thailand only. See also Remarks and Fig. 40 .

Remarks

The species collected from northern Malaysia was mentioned as Plectopylis revoluta ( Pfeiffer, 1867) in the literature (see above). Plectopylis revoluta , however, was originally described from the Andaman Islands. Gude (1914b) discussed the taxonomic status of P. revoluta in detail, and concluded that revoluta is possibly a synonym of P. cyclaspis . The absence of the types of P. revoluta does not allow clarification of this question, but the original description of P. revoluta (e.g., body whorl acutely keeled) certainly does not fit the Malaysian species. Therefore, a new name must be given to this species.

The sample collected by Brandt in 1966 was distributed to several museums (ZMH, NHMW, SMF, MNHN). According to the label the locality is “ Satun: Ban Rae”. The locality name “Ban Rae” probably refers to Ban Rae Kot, northwest of Mueang Satun.

Figures

Fig. 35. Parietal (A–E, G, I–L, N) and palatal (F, H, M, O) plication of species of Plectopylis Benson, 1860. A. P. anguina Gould, 1847, paralectotype (NHMUK 20140812). B. P. repercussa Gould, 1856, lectotype (MCZ 169336). C. P. bensoni var. repercussoides Gude, 1899, holotype (NHMUK 1922.8.29.46). D. P. cairnsi Gude, 1898, holotype (NHMUK 1922.8.29.47). E–F. P. cairnsi (UF 76761). G–H. P. crassilabris sp. nov., paratype (UF 448577). I. P. cyclaspis Benson, 1859 (NHMUK 1906.02.02.148). J. P. karenorum (W. Blanford, 1865) from “Pegu”, Myanmar (NHMUK). K. P. linterae var. fusca Gude, 1898 (NHMUK 1888.12.04.1541–3). L–M. P. malayana sp. nov., paratypes from the type locality (coll PGB). N–O. P. thompsoni sp. nov., paratype (UF 448578). Arrows below the letters indicate the direction of the aperture. Not to scale.

Fig. 40. Distribution of species of Plectopylis Benson, 1860 in Southern Thailand and northern Malaysia. Legends: empty triangle = P. thompsoni sp. nov.; square = P. cairnsi Gude, 1898; filled triangle = sympatric locality of P. thompsoni sp. nov. and P. cairnsi; circle = P. malayana sp. nov.