Tonkinospira triangulata Páll-Gergely & Vermeulen, 2019

Páll-Gergely, Barna, Grego, Jozef, Vermeulen, Jaap J., Reischütz, Alexander, Hunyadi, András & Jochum, Adrienne, 2019, New Tonkinospira Jochum, Slapnik & Páll-Gergely, 2014 species from Laos and Vietnam (Gastropoda: Pulmonata: Hypselostomatidae), Raffles Bulletin of Zoology 67, pp. 517-535 : 533-534

Tonkinospira triangulata Páll-Gergely & Vermeulen , new species

( Figs. 12 , 13 )

Type material. Holotype (H: 1.83 mm, D: 1.42 mm, Fig. 12 ) ( NHMUK 20190687 ), Vietnam, Quang Ninh Province,

Halong Bay area , Dao Bo Hon, Song Sot Cave, drift material washed together over sinkhole in cave, 20°50.833′N, 107°5.667′E, coll. Vermeulen, J.J. & Whitten, A.J., 02 October 1998; 3 cleaned paratypes ( Fig. 13 ) + 96 noncleaned paratypes + some fragments/juveniles ( JJV 6265 ), same data as preceding ; 84 paratypes ( JJV 6244 ), same data as preceding ; 5 paratypes (ZRC.MOL.015615), same data as preceding ; 5 paratypes ( HNHM 104433 ), same data as preceding .

Diagnosis. A medium sized Tonkinospira species with a convexly conic shell, rounded body whorl, dense spiral striation, and a peristome that is not adnate to penultimate whorl.

Description. Shell medium sized for the genus, convexly conic with pointed apex, greyish-white; protoconch consisting of 1–1.25 whorls, nearly smooth, at the last quarter whorl and near the suture granular with some elevated, serrated calcareous ridges that are partly arranged in a spiral line; entire shell consisting of 5.5–6 whorls, suture deep; teleoconch retiform with some faint, spiral threads; spaces between spiral striae variable in width on frontal view of body whorl, but striae are more equidistant on the umbilical side; aperture almost rounded, peristome very slightly expanded, especially in direction of umbilicus, not thickened, sharp; aperture slightly detached from body whorl in ventral view, turning slightly downwards at ca. 1/5 the diameter of the shell; umbilicus narrow and deep, only very slightly covered by reflected lip.

Measurements (in mm). H = 1.69–2.01, D = 1.42–1.46 (n = 4).

Differential diagnosis. Tonkinospira triangulata new species differs from T. crassicostata new species by the smoother shell and thinner peristome, from T. pauperrima by less bulging whorls and less oblique aperture, and T. tomasini by the smaller size and stronger sculpture and the horizontal alignment of the peristome to the body whorl versus the more oblique alignment in T. tomasini . See also under T. danangensis new species.

Etymology. This species is named after its triangular shell shape.

Figures

Fig. 12. Tonkinospira triangulata Páll-Gergely & Vermeulen, new species, NHMUK 20190687 (holotype).

Fig. 13. Variability within Tonkinospira triangulata Páll-Gergely & Vermeulen, new species (JJV 6265).