Sinoennea variabilis Páll-Gergely & Grego, 2020

Páll-Gergely, Barna, Reischütz, Alexander, Maassen, Wim J. M., Grego, Jozef & Hunyadi, András, 2020, New taxa of Diapheridae Panha & Naggs in Sutcharit et al., 2010 from Laos and Thailand (Gastropoda: Eupulmonata: Stylommatophora), Raffles Bulletin of Zoology 68, pp. 1-13 : 9-12

Sinoennea variabilis Páll-Gergely & Grego , new species

( Figs. 5 , 6 C–E)

Type material. Holotype (1 shell, H: 1.96 mm, D: 1.1 mm; Fig. 5A ) (MNHN-IM-2012-27279), South-Central Laos, Khammouan Province, ca. 37 km east-northeast of Thakhek ( Muang Khammouan), ca. 4.5 km west-northwest of Mahaxai , on and under rocks in dry secondary forest under E exposed cliff, 17°25.956′N, 105°09.669′E, alt. 150 m, locality code: 3L07, coll. A. Abdou & I.V. Muratov, 25 November 2007; 3 paratypes (MNHN-IM-2012-27280), same data as holotype.

Additional material. 1 shell (MNHN-IM-2012-27281), south-central Laos, Khammouan Province, ca. 35 km eastnortheast of Thakhek (Muang Khammouan), ca. 7 km westnorthwest of Mahaxai , on and under rocks in dry secondary forest under south exposed cliff, 17°26.736′N, 105°08.360′E, alt. 169 m a.s.l., locality code: 4L07, coll. A. Abdou & I.V. Muratov, 25 November 2007 ; 2 shells ( JG/2 ), South-Central Laos, Khammouan Province, Tham Don Cave, earthquake Dome , sand sediments at bank of cave river, 17°33.815′N, 104°52.298′E, alt. 160 m a.s.l., locality code: JG2 B, coll. J. Grego, 11 February 2017 .

Diagnosis. A minute species with conical, strongly, regularly ribbed shell, closed umbilicus with a slight inner groove, weak apertural barriers (short parietal lamella, two palatal denticles, and columellar denticle).

Description. Shell whitish, gradually growing to become conical to slender conical or pupiform. Body whorl widest from standard apertural view. Entire shell with 4.75–5 whorls. Due to the obscure boundary between protoconch and teleoconch, size of protoconch could not be determined. Protoconch not glossy, very finely pitted. Teleoconch strongly and regularly ribbed. Whorls strongly bulging, suture deep. Aperture suboval/deformed heart-shaped. Parietal callus rounded, reaches ca. half of preceding whorl, relatively thick, not “smeared” onto preceding whorl. Apertural dentition four or five-fold. Parietal lamella strong, elevated, relatively short. Outer portion slightly bent in palatal direction, inner part bent in columellar direction. Sinulus relatively wide, opens slightly laterally. Palatal denticles pointed, somewhat elongate and situated on a ridge, upper one situated closer to peristome. Columellar tooth moderately deeply situated, small, pointed, not elongated. An additional basal denticle might be present on lip. Peristome thickened, expanded, and slightly reflected. Basal swelling slight, situated in some distance from peristome. Impression anterior to basal swelling not visible. Umbilicus closed, not keeled, inner side with shallow groove.

Measurements. H = 1.44–2.1 mm, D = 0.83–1.1 mm (smallest and largest specimens measured).

Etymology. The specific epithet refers to the extreme variability of shell shape between localities of this new species.

Remarks. Sinoennea atomaria ( Dautzenberg, 1893) is 2.5 mm high according to the original description, therefore a comparison with this new species should be given. However, the examined holotype (MNHN-IM-2000-30895) is a shell fragment of only the apical whorls. The drawing in the original description, however, shows a shell with a last whorl that is partly free from penultimate whorl, whereas in S. variabilis , new species, the body whorl is attached to the preceding whorl.

This species is known from three sites. Two of them (3L07 and 4L07) are situated 2.7 km from each other, whereas the third sample (JG2B) lies 31 km and 34 km from the other two sites, respectively. The type series contained four shells that were very similar to each other. Sample from site 4L07 ( Fig. 5B ) contained a single shell. Sample from site JG2B contained two shells, of which one was slightly smaller than the other and had denser ribs, but their shell shapes were similar. While the shell shape shows conspicuous variability between populations, and rib density differed within and between populations as well, the apertural denticles usually used to distinguish species were indistinguishable in all examined shells. Since our sampling is rather insufficient due to low number of localities and specimens per site, we do not describe the local forms as distinct species, but interpret the variable shell shape as a character irrelevant for species recognition. More detailed sampling should clarify this question in the future.

Figures

Fig. 5. Sinoennea variabilis Páll-Gergely & Grego, new species. A, holotype (3L07); B, 4L07 (not paratype); C, JG2B (not paratype). Scale bar represents 1 mm.

Fig. 6. Synoptic view of Sinoennea and Laoennea, new genus, species of Laos (all species shown) and northern Thailand. A, Laoennea carychioides Páll-Gergely, A. Reischütz & Maassen, new species; B, Sinoennea infantilis Páll-Gergely & Grego, new species; C–E, Sinoennea variabilis Páll-Gergely & Grego, new species; F, Sinoennea sutchariti Páll-Gergely & Hunyadi, new species; G, Sinoennea panhai Páll-Gergely & Hunyadi, new species; H, Sinoennea euryomphala Inkhavilay & Panha, 2016; I, Sinoennea ljudmilena Páll-Gergely, new species; J, Sinoennea lizae Maassen, 2008; K, Sinoennea otostoma Páll-Gergely, A. Reischütz & Maassen, new species; L, Sinoennea angustistoma Páll-Gergely, A. Reischütz & Maassen, new species. Scale bar represents 1 mm.