Angustopila psammion Páll-Gergely, Anker & Vermeulen, 2022

Páll-Gergely, Barna, Jochum, Adrienne, J. Vermeulen, Jaap, Anker, Katja, Hunyadi, András, Örstan, Aydin, Szabó, Ábel, Dányi, László & Schilthuizen, Menno, 2022, The world’s tiniest land snails from Laos and Vietnam (Gastropoda, Pulmonata, Hypselostomatidae), Contributions to Zoology 91, pp. 62-78 : 69-71

Angustopila psammion Páll-Gergely, Anker & Vermeulen , n. sp.

urn:lsid:zoobank.org:act:EAD52AC1-985A-48E7-8AF9-4C2629C416BF

Type material: Vietnam, Quang Ninh Province, Ha Long Bay, Cap La Cave , 20°51.793’N, 107°13.541’E, soil deposit fallen through roof in pristine cave, vegetation outside cave tall and woody, leg. J.J. Vermeulen & K. Anker, 07 March 2018, holotype ( HNHM 104886 ) ; CUMZ 7436 / 2 paratypes ; SMF 365052 / 2 paratypes ; VNMN / 2 paratypes ; ZRC. MOL.23218/ 2 paratypes, jjV 17633/ 409 paratypes .

Diagnosis: An Angustopila species with a depressed-globular shell with dome-shaped spire, thick spiral striae, kidney-shaped aperture with single parietal denticle not reaching parietal callus.

Description: Shell tiny, off-white, depressed-globular form with domed spire; body whorl widest in standard apertural view; protoconch with 1.5 whorls and a minute and very uneven pattern of polygonal, rather sharp-crested ridges locally forming minute, conical peaks where ridges split (the structure also reminiscent of cross-sectional trabecular bone), no spiral striation discernible; teleoconch ornamented by some weak radial growth lines and much stronger, ropelike, equidistantly-arranged spiral striae (ca. 14–15 on body whorl from standard apertural view); the 3.25–3.5 whorls are separated by a deep suture; whorls slightly shouldered; aperture oblique to shell axis in lateral view; umbilicus relatively wide, less than one third of shell width; aperture kidney-shaped with strongly concave parietal side; sinulus wide, weakly separated due to weak parietal tooth; peristome expanded, not reflected; parietal callus strongly protruding, but in line with curvature of penultimate whorl and beyond aperture edge (profile) in lateral view ( fig. 3C ), detached from penultimate whorl; parietal tooth weak, low, short, rounded, does not reach peristome.

Soft anatomy unknown.

Measurements (in mm): SW = 0.6–0.68, SH = 0.46–0.57 (n = 24).

Differential diagnosis: Angustopila pallgergelyi Dumrongrojwattana, Chuenit & Wongkamhaeng, 2021 is similar in shell and aperture shape, but is larger, has a prominent palatal tooth (absent in Angustopila psammion n. sp.)and a stronger parietal tooth. Angustopila coprologos n. sp. is slightly larger, has a rough shell surface, and has an additional subcolumellar tooth and two palatal teeth.

Etymology: The specific epithet (ΨαμμϯΟν) means a grain of sand in Greek and is used as a noun in apposition.

Distribution: This new species is known only from the type locality, Cap La Cave, Ha Long Bay, Quang Ninh Province, Vietnam.

Habitat: Angustopila psammion n. sp. was found in large numbers in small sediment deposits along the walls of a dry cave (Cap La Cave), in complete darkness. We assume that the sediment had fallen in through crevices in the rock, because it contains a species-rich assemblage of bleached, opaque shells of surface-dwelling terrestrial gastropods. Shells of Angustopila psammion n. sp., however, look fresh and are probably autochthonous.

Figures

FIGURE 3 Angustopila psammion n. sp. A:paratype, B–I: holotype.