Clostophis incurvus Páll-Gergely & Vermeulen, 2020

Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Reischütz, Alexander, Buczkó, Krisztina & Vermeulen, Jaap J., 2020, Clostophis Benson, 1860, is not a monotypic diplommatinid but a speciose hypselostomatid (Gastropoda: Eupulmonata), with descriptions of six new species, Raffles Bulletin of Zoology 68, pp. 350-368 : 352-358

Clostophis incurvus Páll-Gergely & Vermeulen , new species

( Fig. 4 )

Type material. Holotype (SH: 1.25 mm, SW: 1.08 mm) ( NHMUK 20191125 ; original inv. number: JJV 6263 ), Vietnam, Quang Ninh Province, Halong Bay area, Dao Bo Hon, Song Sot Cave , 20°50.833′N, 107°5.667′E, drift material washed together over sinkhole in cave, coll. Vermeulen, J.J. & Whitten, A.J., 02 October 1998.

Diagnosis. A convexly conical Clostophis species with strong spiral striae, a well-developed parietal and a blunt palatal tooth.

Description. Shell triangular, convex, widest at its base. Whorls regularly increasing, bluntly shouldered. Protoconch consisting of ca. 1.5 whorls, no notable sculpture visible. Entire shell consisting of nearly five whorls, with fine, irregular radial growth lines and stronger, dense, equidistant spiral striae. Body whorl with ca. 17 spiral striae from apertural view. Umbilicus relatively narrow, occupies less than one third of the width. Aperture slightly oblique to shell axis, subcircular with blunt sinulus area. Parietal callus rather sharp, not smeared to penultimate whorl. Peristome relatively strongly thickened and expanded, not reflected. Parietal tooth moderately elevated, situated close to parietal callus. Parietal wall with a low, blunt, but strong tooth.

Differential diagnosis. Clostophis stochi has a weaker and denser spiral striation, a narrower umbilicus, and more rounded whorls. Clostophis multiformis , new species, possesses no or a weaker palatal tooth and a lower parietal tooth. See also under C. koilobasis , new species.

Etymology. The specific epithet means bent, curved in Latin, and refers to the last whorl, which is curved inwards in relation to the penultimate whorl.

Remarks. Although only a single shell is available, its shell characters clearly indicate that it differs from all congeners.

However, future efforts should focus on collecting more shells in order to reveal the intraspecific variability.

Figures

Fig. 4. Clostophis incurvus Páll-Gergely & Vermeulen, new species (NHMUK 20191125, holotype). A, apertural view; B, dorsal view; C, ventral view; D, lateral view; E, protoconch sculpture; F, aperture dentition; G, sculpture of the ventral side; H, sculpture of body whorl (lateral side is shown since the part from standard apertural view has been broken off).