Plectopylis crassilabris, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 89-91

Plectopylis crassilabris sp. nov.

urn:lsid:zoobank.org:act:4CA2A554-40F3-4F82-91E2-A83C03DBD696

Figs 35 G–H, 38E–F, 41A–D, 42

Diagnosis

A large, sinistral species with few (5.25–5.5) whorls, narrow umbilicus and conspicuously thickened peristome; apertural fold short, main plica absent.

Etymology

The name of the new species is derived from its conspicuously thickened lip, from the latin ‘ crassus ’, meaning ‘strong’ and ‘ labris ’, meaning ‘lip’.

Material examined

Holotype

THAILAND: 1 shell (D = 22.5 mm), Chon Buri Province, Khao Cha Ang , ca 17 km ESE/ 4 km S of Om Phanom, 13°10′57″ N, 101°35′16″ E, 150 m a.s.l., 26 Apr. 1987, F.G. Thompson leg. ( UF 279203).

Paratypes THAILAND: 89 shells, same data as for holotype ( UF 448577); 15 specimens (preserved in ethanol: PL006 used for molecular study), same data as for holotype ( UF 279204); 2 shells, same data as for holotype ( HNHM 97461); 53 shells, on the border of Rayong and Chantaburi Provinces, Khao Wangse, 13 km N of Ban Na Yai Aun, 12°53′13″ N, 101°49′2″ E, 100 m a.s.l., 12 May 1987, F.G. Thompson leg. ( UF 346377); 2 shells, same data as for preceding ( HNHM 97475); 16 specimens (preserved in ethanol: PL088 and PL089 used for molecular study), same data as for preceding ( UF 343899); 93 shells, Chachoengsao Province, Khao Tham Raet, 5 km ENE of Ban Non Khok, 13°26′6″ N, 101°44′10″ E, 100 m a.s.l., 11 May 1987, F.G. Thompson leg. ( UF 346364); 5 shells, same data as for preceding ( UF 346374); 3 shells, same data as for preceding ( HNHM 97462); 10 specimens (preserved in ethanol: PL074 and PL075 used for molecular study), same data as for preceding ( UF 376790); 5 shells, Eastern Thailand, Rayong Province, Khaochamao District, Wat Khao Pratun, 13.124312° N, 101.596876° E, 15 Jun. 2007, P. Dumrongrojwattana leg. (coll. PGB); 1 shell, same data as for preceding ( SMF 349028); 1 paratype, same data as for preceding ( NHMB 551276); 6 shells, eastern Thailand, Chonburi Province, Bathong District, Kangkhaw Cave, 13.199314° N 101.579334° E, 22 Aug. 2008, P. Dumrongrojwattana leg. (coll. PGB); 12 shells, eastern Thailand, Chantaburi Province, Kanghangmaen District, Khaowongkot, 12.883881° N, 101.818037° E, 13 Jun. 2007, P. Dumrongrojwattana leg. (coll. PGB); 2 shells, eastern Thailand, Chantaburi Province, Kanghaenhmaew District, Khaowonggot Temple, 13 Jan. 2009 (coll. HGL 0000728385).

Additional material

THAILAND: 4 juv. shells, same data as for holotype ( UF 448577); 1 juv. shell, Chom Buri Province, limestone knoll ca 17 km ESE of Om Phanom, 13°11′6″ N, 101°40′8″ E, 160 m a.s.l., 10 May 1987, F.G. Thompson leg. ( UF 346464); 3 juv. shells, on the border of Rayong and Chantaburi Provinces, Khao Wangse, 13 km N of Ban Na Yai Aun, 12°53′13″ N, 101°49′2″ E, 100 m a.s.l., 12 May 1987, F.G. Thompson leg. ( UF 346377); 19 juv. shells, Chachoengsao Province, Khao Tham Raet, 5 km ENE of Ban Non Khok, 13°26′6″ N, 101°44′10″ E, 100 m a.s.l., 11 May 1987, F.G. Thompson leg. ( UF 346364).

Description

SHELL. Sinistral, strongly built, brownish corneous (most examined shells were heavily weathered); ventral side with reddish and paler mosaic-like structure; protoconch with fine wrinkles, teleoconch with very fine, irregular growth lines and weak spiral structure; whorls 5.25–5.5; umbilicus conspicuously narrow; peristome strongly thickened and slightly reflected with a parietal callus of the same thickness; apertural fold short, in contact with parietal callus.

Five shells were opened. Lambda-complex complete; upper branch long, main plica absent. Palatal plicae typical of Plectopylis .

MEASUREMENTS (in mm). D = 17.3–20.1, H = 6.6–8.0 (UF 346364, n = 4); D = 20.4–23.7, H = 7.7–8.7 (UF 448577, n = 4).

CHARACTERS OF THE GENITAL SYSTEM. Two specimens were examined (one from sample UF 279204, one from UF 343899). Left ommatophoral retractor runs between penis and vagina; penis relatively long, proximally sculptured with parallel, longitudinal, serrate folds, distally sculptured with transverse folds; calcareous crystals were found in penis lumen; epiphallus and vas deferens attached to penis with weak muscle fibres; no penial caecum observed; retractor muscle thick, inserted on penis proximally; vagina slightly shorter and thicker than penis, internally with parallel wrinkled folds and calcareous crystals; bursa copulatrix with a short, relatively slender stalk and an elongate ovate bursa; diverticulum ovate, approx. as long as stalk of bursa copulatrix; diverticulum of specimen from sample UF 343899 contained a spermatophore, which is a long, fragile, reddish brown thread-like tube folded multiple times, forming an ovate mass with pointed ends.

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

Differential diagnosis

Plectopylis crassilabris sp. nov. is easily distinguished from its relatives by the narrow umbilicus, thickened peristome and the absence of a long plica on the parietal wall. The most similar species in terms of shell characters is P. linterae ; for comparisons see under that species.

Distribution

The species is known from southern Thailand (Chon Buri, Rayong and Chachoengsao Provinces) ( Fig. 12 ).

Remarks

The specimens from Chachoengsao Province (UF 346364) are smaller and have a much thicker peristome than the individuals from the other two provinces. The traits of the genital anatomy (absence of penial caecum, short, ovoid diverticulum) suggest that the closest related species to Plectopylis crassilabris sp. nov. is P. cairnsi .

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. 12. Distribution of plectopylid species in Thailand, Laos and Myanmar. Legends: circle = Chersaecia shanensis (Stoliczka, 1873); filled square = Chersaecia reversalis sp. nov.; empty square = Chersaecia dextrorsa (Benson, 1860); empty rhomb = Hunyadiscus tigrina sp. nov.; filled rhomb = Hunyadiscus saurini Páll-Gergely, 2016; triangle, top up = Plectopylis crassilabris sp. nov.; triangle, top down = Naggsia laomontana (L. Pfeiffer, 1862); empty triangle, top down = Plectopylis bensoni Gude, 1914.