Angustopila bidentata Pall-Gergely & Jochum, 2023

Pall-Gergely, Barna, Hunyadi, Andras, Vermeulen, Jaap J., Grego, Jozef, Sutcharit, Chirasak, Reischuetz, Alexander, Dumrongrojwattana, Pongrat, Botta-Dukat, Zoltan, Oerstan, Aydin, Fekete, Judit & Jochum, Adrienne, 2023, Five times over: 42 new Angustopila species highlight Southeast Asia's rich biodiversity (Gastropoda, Stylommatophora, Hypselostomatidae), ZooKeys 1147, pp. 1-177 : 1

Angustopila bidentata Pall-Gergely & Jochum sp. nov.

Fig. 63

Type material.

Holotype: Laos • 1 empty shell (H: 0.88 mm, D: 0.8 mm); South-Central Laos, Khammouane Province, ca. 35 km ENE of Thakhek (Muang Khammouane), ca. 7 km WNW of Mahaxai, on and under rocks in dry secondary forest under S exposed cliff (locality code: 4L07); 17°26.74'N, 105°08.36'E; 25 Nov. 2007; A. Abdou & I.V. Muratov leg.; MNHN-IM-2014-6411.

Paratypes: Laos • 3 shells; same data as for holotype; MNHN-IM-2014-6412 • 2 shells; South-Central Laos, Khammouane Province, ca. 15 km NE of Thakhek (Muang Khammouane), ca. 12.5 km SE of Ban Nase, on and under rocks in dry secondary forest near large flooded cave under W exposed cliff (locality code: 7L07); 17°30.55'N, 104°53.44'E; 130 m a.s.l.; 28 Nov. 2007; A. Abdou & I.V. Muratov leg.; MNHN-IM-2014-6410 • 12 shells (some are damaged); South-Central Laos, Khammouane Province, ca. 37 km ENE of Thakhek (Muang Khammouane), ca. 4.5 km WNW of Mahaxai, on and under rocks in dry secondary forest under E exposed cliff (locality code: 3L07); 17°25.96'N, 105°09.67'E; 150 m a.s.l.; 25 Nov. 2007; A. Abdou & I.V. Muratov leg.; MNHN-IM-2014-6409 • 10 adult shells; Khammouane Province, 17.5 km from centre of Thakhek towards Mahaxay, Tham Nang Aen (cave) (locality code: 2019/96); 17°26.65'N, 104°57.02'E; 190 m a.s.l.; 27 Sep. 2019; A. Hunyadi leg.; coll. HA • 5 shells; South-Central Laos, Khammouane Province, ca. 10.5 km E of Thakhek (Muang Khammouane), on and under rocks, cave deposits, in secondary forest under entrance and in large cave on exposed NE steep slope (locality code: 25L07); 17°24.34'N, 104°54.89'E; 160 m a.s.l.; 9 Dec. 2007; A. Abdou & I.V. Muratov leg.; MNHN-IM-2014-6408 • 1 damaged shell; Khammouane Province, Tham Nam Dôn Cave, sediment deposited by temporary side rivulet at passage entrance (locality code: JG2A); 17°33.82'N, 104°52.30'E; 160 m a.s.l.; 11 Feb. 2017; J. Grego leg.; coll. JG • 1 shell; Khammouane Province, Tham Nam Dôn Cave, Earthquake Dome, sand sediments at bank of river in cave (locality code: JG2B); 17°33.82'N, 104°52.30'E; 160 m a.s.l.; 11 Feb. 2017; J. Grego leg.; coll. JG • 1 shell; Khammouane Province, Tham Pha Inh (cave), E Thakhek, at the base of limestone rocks (Locality code: La.7); 17°27.69'N, 104°54.95'E; 180 m a.s.l.; Mar. 2010; A. Reischütz leg.; coll. RE • 1 shell; Khammouane Province, 40 km from centre of Thakhek towards Mahaxay, 2.3 km southeast from Ban Na Coc, rock wall (locality code: 2019/95); 17°25.96'N, 105°09.67'E; 155 m a.s.l.; 29 Sep. 2019; A. Hunyadi leg.; coll. HA.

Additional material.

Laos • 1 damaged shell with missing aperture (identity questionable, not paratype, much smaller than other shell from the same locality, see remarks); Khammouane Province, Tham Nam Don Cave , sediment deposited by temporary side rivulet at passage entrance (locality code: JG2A); 17°33.82'N, 104°52.30'E; 160 m a.s.l.; 11 Feb. 2017; J. Grego leg.; coll. JG • 6 j/b shells; Khammouane Province, 17.5 km from centre of Thakhek towards Mahaxay, Tham Nang Aen (cave) (locality code: 2019/96); 17°26.65'N, 104°57.02'E; 190 m a.s.l.; 27 Sep. 2019; A. Hunyadi leg.; coll. HA .

Diagnosis.

A small to large Angustopila species with a very wide sinulus, an oblique aperture, a very narrow umbilicus, and strong parietal and upper palatal teeth.

Description.

Shell small to large for the genus (mostly medium sized), higher than wide, or rarely slightly wider than high; pale grey, conical-globular, last or penultimate whorl widest from standard apertural view; protoconch consists of 1.5 whorls, with fine spiral striation on the entire protoconch (five spiral lines visible); teleoconch finely ornamented with irregularly spaced radial growth lines crossed by fine rows of regularly or irregularly spaced spiral striae (ca. 13-19 on body whorl from apertural view); on frontal and ventral surface of body whorl spiral and radial lines of comparable strength, or spiral ones dominant; whorls 4.5, slightly shouldered; aperture very strongly oblique to shell axis from lateral view; umbilicus, very narrow; aperture reniform, sinulus wide and strongly separated by parietal and palatal teeth; peristome slightly expanded, not reflected; mid-section comprising the parietal tooth sinuous and slightly protruding (in side view); aperture detached from the penultimate whorl forming a short, downward-directed tubus (lateral view); parietal callus strongly elevated, sharp; parietal tooth strongly developed and pointed towards the palatal tooth, which is situated high up on the palatal side; parietal and palatal teeth are directly opposite to each other.

Measurements (in mm).

H = 0.8-1.1, D = 0.75-0.95, H/D*100 = 98.8-115.4 (n = 8, from populations excluding JG2A), RUD = 18.7-25.8 (n = 10); H: 1.21, D = 1.09, H/D*100 = 111 (JG2A).

Differential diagnosis.

Angustopila bidentata sp. nov. can be distinguished from all other Angustopila species by the presence of two apertural denticles on a semi-detached tuba and the strongly oblique, wing-shaped aperture formed by the very wide sinulus and a very narrow umbilicus. The latter two traits allow the distinction of this species from congeners even at the juvenile stage. The most similar species is probably A. dominikae , which has an oblique, oblong, and adnate aperture, and a more globular shell. See also under A. erawanica sp. nov., A. huoyani , and A. tamlod .

Etymology.

The specific epithet Angustopila bidentata (Latin, meaning two-teeth) refers to the two strongly developed apertural teeth of this new species.

Distribution.

Angustopila bidentata sp. nov. is known from Khammouane Province of Laos, in the limestone area east of Thakhek (Fig. 64 ).

Remarks.

This species shows a considerable variability in terms of shell size and some conchological characters. The populations JG2B, 3L07, 4L07, and 7L07 are indistinguishable from each other. Shells of population 25L07 are slightly larger than those in the other populations and bear a more elongated (less rounded) aperture, denser spiral striae, and show stronger radial sculpture. The single shell of the sample JG2A is very large compared to the others, and has a rounded aperture, similar to shells of the four aforementioned populations. The single shell from locality JG2A was already cracked and was subsequently damaged during imaging. However, other than shell size, no obvious morphological differences warrant distinction of that large specimen from the remaining A. bidentata sp. nov. shells. A single, toothless juvenile shell, similar in size to typical A. bidentata sp. nov., was also found in the same locality (JG2A). If that shell was an A. bidentata sp. nov. individual, then the large shell of the same locality represents a distinct species.

Figures

Figure 63. Angustopila bidentata Pall-Gergely & Jochum, sp. nov. (holotype, MNHN-IM- 2014 - 6411). Apertural (A), ventral (B), apical (C) and lateral (D) sides of the shell; sculpture on the protoconch (E), aperture (F); ventral (G) and frontal (H) surface of the body whorl.

Figure 64. Distribution of Angustopila species in Laos.