Angustopila tonkinospiroides 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 tonkinospiroides Pall-Gergely & Vermeulen sp. nov.

Fig. 23

Type material.

Holotype: Vietnam • 1 empty shell (H: 1.07 mm, D: 0.88 mm); Quang Ninh Province, Halong Bay area, Dao Bo Hon, Song Sot Cave, drift material washed together over sinkhole in cave; 20°50.83'N, 107°05.67'E; 2 Oct. 1998; J.J. Vermeulen & A.J. Whitten leg.; HNHM 100179.

Paratypes: Vietnam • 400 shells; same data as for holotype; JJV 17655 (ex JJV 6263) • 10 shells; same data as for holotype; coll. HA • 31 shells; Haiphong Province, Cat Ba Island, Cave Minh Chou, inside cave, cave with freshwater stream flowing into the sea, much disturbed by water extraction and concrete paths; 20°45.21'N, 107°0.75'E; 50 m a.s.l.; 5 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 18885 (ex JJV 16610).

Diagnosis.

A medium-sized to large, toothless Angustopila species with a conical spire, wide penultimate whorl, and a narrow, subovate-shaped umbilicus.

Description.

Shell normal- to large-sized for the genus, (much) higher than wide; pale grey; shell shape conical, penultimate whorl is the widest in standard apertural view; protoconch consists of 1.5 whorls, with spiral striation preceding the first teleoconch whorl; teleoconch finely ornamented with usually weak, irregularly spaced radial growth lines crossed by fine rows of somewhat stronger, equidistantly-spaced spiral threads (ca. 20 in standard apertural view); whorls 4.5-4.75, rounded, but rather irregular, with some traces of compression of the convex whorls from lateral/umbilical direction; aperture slightly curved and oblique to shell axis from lateral view; umbilicus narrow, eccentrically teardrop-shaped due to unusual coiling of body whorl, concentric spiral striation intensified around umbilicus; aperture subovate with straight parietal side; peristome slightly expanded, not reflected, rather sharp; parietal callus slightly protruding, detached from penultimate whorl; aperture toothless, a fine swelling discernible just behind peristome, running parallel with it.

Measurements (in mm).

H = 0.98-1.16, D = 0.85-0.95, H/D*100 = 104.3-128.9 (n = 14), RUD = 22.7-28.9 (n = 4).

Differential diagnosis.

The irregularly growing whorls, the higher than wide, rather large shell, the toothless aperture and the teardrop-shaped umbilicus distinguishes this species from its congeners. Angustopila thersites sp. nov. is smaller, and has a concave-conical, more irregularly increasing shell. Angustopila fratermajor sp. nov. is smaller, has a parietal tooth, and possesses a wider umbilicus. Tonkinospira species are usually larger, depressed-conical in shape and have denser spiral striation on both the protoconch and teleoconch.

Etymology.

First we considered this species to belong to the genus Tonkinospira. Due to the tonkinospirid aspects (i.e., large conical shell, regularly growing whorls, superficial microstructure and lack of apertural dentition), the specific epithet reflects this similarity.

Distribution.

This new species is known from two sites in the Halong Bay area in northern Vietnam (Fig. 24 ).

Figures

Figure 23. Angustopila tonkinospiroides Pall-Gergely & Vermeulen, sp. nov., JJV 6263. Paratype (A) and holotype (HNHM 100179) (B-H). Apertural (A, C), ventral (E), apical (D) and lateral (B) sides of the shell; sculpture on the protoconch (F), ventral (G) and frontal (H) surface of the body whorl.

Figure 24. Distribution of Angustopila species in the Halong Bay area.