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

Figs 20 , 21

Type material.

Holotype: Vietnam • 1 empty shell (H: 0.85 mm, D: 0.86 mm); Quang Ninh Province, Halong Bay area, Phao Trong Island (locality code: WMVT.0333); approx. GPS code: 20°49.80'N, 107°08.32'E; 11 Sep. 2003; W.J.M. Maassen leg.; RMNH 347760.

Paratypes: Vietnam • 9 adult shells; same data as for holotype; RMNH 347761 • 3 shells; Quang Ninh Province, Halong Bay area, Luoi Liem Island; 20°49.67'N, 107°09.90'E (locality code: WMVT.0334); 12 Sep. 2003; W.J.M. Maassen leg.; RMNH 347762 • 1 shell; Haiphong Province, Cat Ba Island, Cave Qua Vang, around cave entrance, rocky limestone slope with low, rather mature forest; 20°48.64'N, 107°04.64'E; 100 m a.s.l.; 6 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16621 • 7 shells; Haiphong Province, Cat Ba Island, Cave Qua Vang, inside cave, large, little disturbed active cave with speleothems; 20°48.64'N, 107°04.64'E; 60 m a.s.l.; 6 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16620 • 8 shells; Haiphong Province, Cat Ba Island, Cave Xa Bac, around cave entrance; 20°50.07'N, 106°58.61'E; 30 m a.s.l.; 9 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16599 • 15 shells; 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.; JJV 17654 (ex JJV 6237) • 1 shell; Haiphong Province, Cat Ba Island, along trail from headquarters to Viet Hai, along Ao Eck, sampling starting at coordinates, until 0.5 km beyond Ao Eck; 20°48.07'N, 107°00.83'E; 100 m a.s.l.; 4 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16618 • 4 shells; Haiphong Province, Cat Ba Island, Cave Uy Ban, around cave entrance; 20°46.39'N, 107°00.88'E; 40 m a.s.l.; 9 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16623 • 7 shells; Haiphong Province, Halong Bay area, unnamed island off E Coast Cat Ba, south facing bay with beach and densely vegetated limestone scree slope; 20°45.19'N, 107°04.45'E (approximate GPS data); 1 Oct. 1998; J.J. Vermeulen & K. Anker leg.; JJV 6236 • 2 shells; Haiphong Province, Cat Ba Island, large, somewhat disturbed, active cave with speleothems; 20°50.06'N, 106°55.91'E; 0-50 m a.s.l.; 7 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16622 • 4 shells; Quang Ninh Province, Halong Bay area, unnamed island 1.8 km W of S point Cong Tai Island, steep limestone slope bordering beach, dense vegetation; 20°52.23'N, 107°18.25'E; 3 Oct. 1998; J.J. Vermeulen & A.J. Whitten leg.; JJV 6239 • 25 shells; Haiphong Province, Cat Ba Island, Cave Trung Trang, around cave entrance, steep limestone cliffs with vegetated ledges; 20°47.30'N, 106°59.84'E; 50 m a.s.l.; 6 Jun. 2017; J.J. Vermeulen & K. Anker leg.; JJV 16619 • 5 shells; same data as for preceding; coll. HA.

Additional material.

Vietnam • 2 j/b shells; same data as for holotype; RMNH 347763 • 7 shells; Quang Ninh Province, Halong Bay area, Thay Cave on Congfo Island , collected inside the cave; 20°52.07'N, 107°12.06'E (locality code: WMVT.0327); 6 Sep. 2003; W.J.M. Maassen leg.; RMNH 347764 .

Diagnosis.

A small to medium-sized, concave-conical species with irregularly growing whorls, strong spiral striation, very narrow umbilicus, and a strongly oblique, toothless aperture.

Description.

Shell small to medium-sized for the genus, mostly wider than high or rarely higher than wide (see population WMVT.0327), concave-conical, tightly and asymmetrically coiled, seemingly globular due to narrowing last whorl; body whorl widest in apertural view (although slightly wider than penultimate whorl) or penultimate whorl widest; protoconch bulbous, consists of ca. 1.25 whorls, with weak spiral striation preceding the first teleoconch whorl; teleoconch with irregular radial growth lines and dense, strong, rather regular wavy spiral striation (ca. 22 spiral striae on body whorl in apertural view); whorls 3.5-3.75, rounded; aperture curved and strongly oblique to shell axis in lateral view; aperture ovate-oblong; aperture tucked tightly under inflated penultimate whorl in apertural view; peristome slightly expanded, not reflected; not attached to penultimate whorl; umbilicus very narrow, ca. 1/5 of shell width; aperture toothless.

Measurements (in mm).

H = 0.75-0.87, D = 0.81-0.93, H/D*100 = 87.2-101.2 (n = 10), RUD = 23.5-24.1 (n = 3) (populations except for WMVT.0327); H = 0.81-0.85, D = 0.87-0.93, H/D*100, = 102.4-114.8, RUD = 22.2-24.7 (n = 2, WMVT.0327).

Differential diagnosis.

The most similar species is A. megastoma sp. nov., which also occurs sympatrically with this species. Distinguishing these two species is sometime difficult because both have quite an irregular shell, and exhibit a rather large intraspecific variability. Nevertheless, there are several differences as follows: A. megastoma sp. nov. is larger, and has a generally lower spire; its aperture is less rounded (rather semilunar because the body whorl is more attached to the penultimate whorl); the spiral striation of A. megastoma sp. nov. is denser and much fainter, in fact it is nearly invisible under the stereo microscope (only visible with SEM); the last whorl of A. megastoma sp. nov. is wider compared to the penultimate whorl than that of A. thersites sp. nov. (in the latter species often the penultimate whorl is wider than the last one in apertural view). See also under A. tonkinospiroides sp. nov.

Etymology.

This new species is named after Thersites (Θερσίτης = the ugliest Greek soldier laying siege to Troy) referring to the irregularly growing whorls.

Distribution.

This species is known from several sites in the Halong Bay Area, northern Vietnam (Fig. 22 ).

Remarks.

Shells from sample WMVT.0327 are unusually high-spired and are less concave-conical (some of them are even conical) than typical A. thersites sp. nov. shells. Although the differences in shell shape between most shells of sample WMVT.0327 and other A. thersites sp. nov. shells are obvious, the shell with the lowest spire of sample WMVT.0327, and the shell with the highest spire of the other A. thersites sp. nov. samples are very similar. In addition, the strong spiral striation, the aperture shape, the narrow umbilicus, and the very oblique aperture suggests that they are conspecific with A. thersites sp. nov.

Figures

Figure 20. Angustopila thersites Pall-Gergely & Vermeulen, sp. nov. A paratype (RMNH 347761) B-H holotype (RMNH 347760). Apertural (A, B), lateral (C), ventral (D) and apical (E) sides of the shell; granular sculpture on the protoconch (F), ventral (G) and frontal (H) surface of the body whorl.

Figure 21. Angustopila thersites Pall-Gergely & Vermeulen, sp. nov., sample WMVT. 0327 (RMNH 347764) A specimen 2 B-I specimen 1. Apertural (A, B), lateral (C), ventral (D) and apical (E) sides of the shell; granular sculpture on the protoconch (F), aperture (G), ventral (H) and frontal (I) surface of the body whorl.

Figure 22. Distribution of Angustopila species.