Hypselostoma similare Gojšina, Hunyadi & Páll-Gergely, 2025

Hypselostoma similare Gojšina, Hunyadi & Páll-Gergely sp. nov.

Figs 242 H View Figure 242 , 257 View Figure 257 , 258 View Figure 258 , 259 View Figure 259

Type material.

Holotype. Thailand • 1 shell (SH: 1.83 mm; SW 1: 2.51 mm); Rayong Province, Khao Chamao district, Wat Tham Khao Prathun , gorge above the temple; 13°07.439'N, 101°35.850'E; 115 m a. s. l.; 09 Mar. 2023, A. Hunyadi leg.; CUMZ 14470 View Materials GoogleMaps . Paratypes. Thailand • 2 shells; same data as for holotype; coll. HA GoogleMaps .

Type locality.

Thailand, Rayong Province, Khao Chamao district, Wat Tham Khao Prathun, gorge above the temple; 13°07.439'N, 101°35.850'E; 115 m a. s. l.

Diagnosis.

Shell triangular conical. Teleoconch almost smooth, finely radially but not spirally striated. Last whorl detached from the penultimate and ascending, keeled below the centre of the periphery. Aperture equipped with weak barriers, five main (angular, parietal, upper palatal, lower palatal and columellar) and several smaller ones. Umbilicus narrow, measuring 1 / 7–1 / 8 of the shell width.

Description.

Shell conical, light brownish, opaque, consisting of 3.75–4.25 weakly convex and regularly increasing whorls separated by a relatively shallow suture. Protoconch finely pitted, without spiral striae, consisting of ~ 1.5 whorls, same colour as the rest of the shell. Teleoconch sculpture delicate, very finely dimpled (pasty) and crossed by relatively weak radial growth lines. Spiral striae absent. Occasionally, a few stronger whitish radial streaks can be observed at the last whorl near the aperture. Last whorl weakly detached from the penultimate and slightly ascending near the aperture (~ 15–20 ° compared to the shell axis). It is bluntly but prominently keeled below the periphery, making the last whorl oblique to the shell axis and not convex but with a sloping, flat outline. There is a slight furrow above the keel. Peristome thick, whitish, expanded and not reflected. All apertural barriers are weak. Aperture equipped with five main barriers (angular, parietal, upper palatal, lower palatal, and columellar) and several smaller ones of variable number and appearance. There are usually no plicae in the sinulus, usually one plica in the interpalatal region, two or three plicae in the region of the basal plica and usually one or two lamellae in the columello-parietal region. Angular lamella tubercle-like, almost reaching the peristome. Behind it, more deeply situated, there is one additional part which also belongs to the angular lamella. Parietal lamella stronger and higher when compared to the others (except lower palatal plica), not reaching the profile of the angular tubercle. Lower palatal plica developed to the same extent as the parietal lamella and slightly higher and stronger than the upper palatal plica. Columellar lamella horizontal, developed equally as the upper palatal plica. Anterior to the upper palatal plica, there is one more tubercle-like part, possibly homologous with the palatal tubercle found in the genus Bensonella (see Páll-Gergely and White 2023) or it even might represent a part of the upper palatal plica. Weaker barriers are all positioned deeper in the aperture and never reaching the profiles of the main ones. A tubercle-like swelling is present in the columellar-parietal transition embayment. All barriers are strongly and coarsely spiniferous. Sinulus small, rounded and distinctly separated from the rest of the aperture. Umbilicus narrow, with almost perpendicular walls, showing only a part of the penultimate whorl and measuring ~ 1 / 7–1 / 8 of the shell width.

Differential diagnosis.

By its last whorl keeled at its base, this species in superficially most similar to H. insularum and Hypselostoma species inhabiting the Philippines. However, this species most clearly differs from these representatives by the presence of two lamellae on the parietal side (angular and parietal) and more numerous barriers in the aperture including smaller ones. Hypselostoma insularum further has strong spiral striae which are absent in the new species.

Etymology.

Named after the fact that this species is in shell shape very similar to some Hypselostoma species inhabiting the Philippines.

Measurements

(in mm, n = 3). SH = 1.82–1.91; SW 1 = 2.34–2.51; SW 2 = 1.45–1.51; AH = 0.98–1.01; AW = 0.9–0.98.

Distribution.

This species is known only from the type locality.

Remarks.

All barriers in the aperture very weak, smaller ones are hardly observable, only in form of very weak lines. Single interpalatal plica present or absent. Sinulus plicae present or absent.