Angustopila concava (Thompson & Upatham, 1997)

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 concava (Thompson & Upatham, 1997)

Figs 35 , 36

Systenostoma concava Thompson & Upatham, 1997: 231-232, figs 32-38.

Systenostoma concava - Panha and Burch 2005: 118-119, fig. 101.

Angustopila concava - Jochum et al. 2014: 27.

Type locality.

"Thailand, Nakhon Ratchasima Province, limestone hill 3.4 km west of Ban Mu Si, 380 m altitude (14°32.0'N, 101°22.5'E)."

Material examined.

Holotype: Thailand • 1 shell; Nakhon Ratchasima Province, limestone hill 3.4 km west of Ban Mu Si ; 14°32.00'N, 101°22.50'E; 380 m a.s.l.; 5 May 1987; F.G. Thompson leg.; UF 113541 (not figured in the original description).

Paratypes: Thailand • 9 shells; same data as for holotype; UF 113542 .

Diagnosis.

A large (H: 1.02-1.21 mm, D: 1.05-1.12 mm, H/D*100: 91.1-115.2 (n = 5), RUD = 28.3-32.7 (n = 3)), concave-conical Angustopila species with a very strongly oblique aperture, a low parietal tooth reaching peristome edge, a strongly concave parietal callus, and a conspicuously narrow sinulus.

Description.

Shell large for the genus, higher than wide, rarely slightly wider than high; concave-conical, body whorl widest in standard apertural view; protoconch consists of 1.25 whorls with weak spiral striae on the entire teleoconch; teleoconch dominated by an irregularly dimpled, pasty texture, with very fine irregularly spaced, weak radial growth lines crossed with very weak, obscure, sparsely-spaced spiral striae (impossible to count in standard apertural view, but on ventral side they are more widely-spaced than in other Angustopila species); spiral striae overall weaker than in most other Angustopila species; whorls ca. 4.5-4.75, rounded; aperture strongly oblique to shell axis from lateral view; umbilicus wide; aperture ovate-subquadrate, parietal callus concave; sinulus wide, weakly isolated due to the low parietal tooth; peristome expanded, especially on the palatal region, not reflected; parietal callus detached from penultimate whorl, protruding; parietal tooth very low, short, situated close to the parietal callus.

Differential diagnosis.

See under Angustopila erawanica sp. nov., A. occidentalis sp. nov. and A. uvula sp. nov., and under Remarks.

Distribution.

This species is known only from the type locality in Thailand’s Nakhon Ratchasima Province (Fig. 19 ).

Remarks.

The original description mentions a slight tubercular thickening on the palatal lip. We have not found any thickening there that would be similar to the palatal teeth of any other Angustopila species.

Angustopila concava is similar to several populations of A. fabella in terms of shell size and the concave-conical shape, but differs from them in the strongly oblique aperture, the strongly sinuous parietal callus, and the conspicuously pointed (slender) sinulus. The parietal tooth of A. concava is weaker and situated closer to the parietal callus than that of the majority of A. fabella populations. The parietal tooth of only one A. fabella sample (15L06) is situated as close to the parietal callus as are those of A. concava . However, the other traits still differ between A. fabella sample 15L06 and A. concava .

Figures

Figure 19. Distribution of Angustopila species.

Figure 35. Angustopila concava (Thompson & Upatham, 1997), holotype (UF 113541). Apertural (A), lateral (B), apical (C) and ventral (D) sides of the shell; aperture (E, F), microstructure on the protoconch (G), microstructure on ventral (H) and frontal (I) surface of the body whorl.

Figure 36. Angustopila concava (Thompson & Upatham, 1997). Paratypes (UF 113542, carbon-coated shells, probably imaged in the original description) A, B paratype, specimen 1 C, D paratype, specimen 2.