Angustopila oostoma Pall-Gergely & Vermeulen, 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 oostoma Pall-Gergely & Vermeulen sp. nov.

Figs 51 , 52

Type material.

Holotype: Vietnam • 1 empty shell (H: 0.89 mm, D: 0.81 mm); Ninh Binh Province, Cuc Phuong National Park, path to Fairy Cave, primary forest, limestone outcrops in shale bedrock; 20°13.06'N, 105°53.43'E; 10 October 1998; J.J. Vermeulen & L. Deharveng leg.; HNHM 105289 (original inventory number: JJV 6224).

Paratypes: Vietnam • 1 adult shell with imperfectly grown last whorl; Ninh Binh Province, Cuc Phuong National Park, 1 km WNW of Xom Bong, primary forest, small limestone outcrops in clay soil; approximate GPS coordinates: 20°55.57'N, 105°9.24'E; 10 Oct. 1998; J.J. Vermeulen & L. Deharveng leg.; JJV 6251 • 2 shells; Ninh Binh Province, Cuc Phuong National Park, 2 km road Xom Bong to Headquarters, primary forest, limestone outcrops in thick clayey soil; 10 Oct. 1998; J.J. Vermeulen & L. Deharveng leg.; JJV 6222.

Additional material.

Vietnam • 3 adult shells; Hòa Bình Province, Tân L ạc District, 1300 m west from Quy H ậu on road no. 6, rock wall (locality code: 2020/28); 20°37.93'N, 105°16.17'E; 150 m a.s.l.; 11 Feb. 2020; A. Hunyadi leg.; coll. HA • 3 j/b shells; Ninh Binh Province, Cuc Phuong National Park, 2 km road Xom Bong to Headquarters, primary forest, limestone outcrops in thick clayey soil; 10 Oct. 1998; J.J. Vermeulen & L. Deharveng leg.; JJV 17629 (ex 6222) • 1 shell; Ninh Binh Province, Cuc Phuong National Park , Prehistoric Man Cave , steep limestone slope with disturbed forest; 20°17.61'N, 105°40.11'E; 10 Oct. 1998; J.J. Vermeulen & L. Deharveng leg.; JJV 6252 .

Diagnosis.

A medium-sized Angustopila species with a conical shell, an ovate aperture and a deeply-set, weak parietal tooth.

Description.

Shell of normal size for the genus, slightly higher than wide, body whorl widest from standard apertural view; protoconch consists of 1.25-1.5 whorls, with fine spiral striation; specimens from the type locality with weaker, the shell from site 2020/28 with stronger and denser radial lines; typical shells with ca. 14, the shell from site 2020/28 with 19 spiral striae on body whorl from apertural view; whorls 4, rounded; aperture slightly oblique to shell axis from lateral view; umbilicus wide; aperture large, ovoid (higher than wide) to ovate-subquadrate; peristome slightly expanded, not reflected; parietal callus does not elevate from penultimate whorl; parietal tooth elongated, low, deeply-set (does not reach parietal callus).

Measurements (in mm).

H = 0.89-1.0, D = 0.81-0.95, H/D*100 = 105.3-111.6 (n = 7), RUD = 27.4-32.3 (n = 4).

Differential diagnosis.

Generally larger than A. elevata , has a rather conical shell (concave-conical in A. elevata ), a less pointed apex, a wider umbilicus, and a comparatively larger, ovate aperture (although A. elevata samples 2020/18 and 2019/120 have a rather oval aperture) with a weak parietal tooth. In contrast, A. elevata is always toothless. We note that the tooth-like thickening of the parietal callus in one A. elevata shell ( Páll-Gergely et al. 2017: fig. 7F) is not considered to be a tooth. Moreover, although not in all A. elevata populations, the radial sculpture of that species is more prominent. Populations assigned to Angustopila fabella are larger, possess a stronger parietal tooth, a comparatively smaller aperture and usually, a more pointed apex.

Etymology.

The specific epithet refers to the ovoid aperture (ᾠόν = egg, στόμα = mouth).

Distribution.

This new species is known from two sites: the Cuc Phuong National Park (type locality) and another site ca. 40 km northwest (Fig. 48 ).

Remarks.

The single shell collected at the Cave of Prehistoric Man at Cuc Phuong National Park (JJV 6252) lacks a parietal tooth, has a narrower umbilicus, and weaker sculpture than the other A. oostoma sp. nov. shells. Thus, it may belong to a different species. We refer to it herein as A. cf. oostoma sp. nov.

Figures

Figure 48. Distribution of Angustopila species.

Figure 51. Angustopila oostoma Pall-Gergely & Vermeulen, sp. nov. (holotype, HNHM 105289). Apertural (A), apical (B), lateral (C) and ventral (D) sides of the shell; eroded surface showing some microstructure on the protoconch (E), aperture (F), ventral (G) and frontal (H) surface of the body whorl.

Figure 52. Angustopila oostoma Pall-Gergely & Vermeulen, sp. nov. (2020 / 28). Apertural (A), ventral (B), apical (C) and lateral (D), sides of the shell; aperture (E), microstructure of the protoconch showing protoconch-teleoconch boundary (F), ventral (G) and frontal (H) surface of the body whorl.