Hypselostoma sculpturatum Gojšina, Hunyadi & Páll-Gergely, 2025

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

Type material.

Holotype. Cambodia • 1 shell (SH: 2.70 mm; SW 1: 3.80 mm); Steung Treng Province, 36.3 km northwest + 5 km north from Stung Treng Mekong Bridge, Phnom Chhnok ; 13°46.573'N, 105°44.878'E; 120 m a. s. l.; 25 Oct. 2023; A. Hunyadi & J. U. Otani leg.; CUMZ 14458 View Materials . GoogleMaps

Paratypes. Cambodia • 51 shells; same data as for holotype; coll. HA GoogleMaps • 1 shell; same data as for holotype; coll. VG GoogleMaps .

Additional material examined.

Cambodia • 4 shells (juveniles, not paratypes); same data as holotype; coll. HA GoogleMaps .

Type locality.

Cambodia, Steung Treng Province, 36.3 km northwest + 5 km north from Stung Treng Mekong Bridge, Phnom Chhnok; 13°46.573'N, 105°44.878'E; 120 m a. s. l.

Diagnosis.

Hypselostoma species with all teleoconch whorls keeled, detached last whorl and strongly spirally striated shell surface. There are five strong barriers in the aperture (angulo-parietal, upper palatal, lower palatal, basal and columellar). Umbilicus initially narrow, suddenly widening at the last whorl.

Description.

Shell conical-ovoid, brownish, not glossy. It is consisting of 4–4.5 whorls separated by a deep suture. Protoconch rounded, of ~ 1.75 finely pitted whorls of the same colour as the rest of the shell. Teleoconch sculptured with strong, raised spiral striae. Spacing between two striae equals the width of one stria or is twice as wide as a stria. Spiral striae are more densely arranged on the initial teleoconch whorls, and more coarsely on the last whorl. The number of striae on the last whorl is ~ 25 in standard view. There are several white, unevenly positioned, radial streaks crossing the spiral striae. All teleoconch whorls are keeled, and the strength of the keel is increasing towards the last whorl which is especially strongly keeled. Surfaces of the whorls above and below the centrally positioned keel are flat, to very slightly concave (above the keel on the last whorl). Last whorl moderately detached from the penultimate, distanced from the shell axis. From the lateral view (Fig. 168 B View Figure 168 ), it can be seen that the last whorl is initially slightly ascending and then straightening right near the aperture so that the aperture profile is almost parallel to the shell axis (leaving the aperture only slightly ascending at ~ 5–10 ° compared to the shell axis). Peristome light brownish, expanded and not reflected. Aperture equipped with five barriers (angulo-parietal, upper palatal, lower palatal, basal, and columellar). Angulo-parietal strong and high, lamella usually appears as a single barrier (parietal) but has a very short swollen part in front of it which most probably represents the remains of the angular part. Upper palatal plica moderately high, slightly curved towards the lower palatal plica (somehow similar to the upper palatal plica in H. serpa ). Lower palatal plica slightly higher, longer, and more slender than the upper palatal but similar in width. It is pointing towards the embayment between the columellar and parietal lamellae. Basal plica more closely positioned to the lower palatal (not in its usual position between the lower palatal and columellar), ~ 2 × lower than the latter and short. Columellar lamella thick and broad, more closely resembling a very large swelling than a distinct barrier. There is also a small swelling between the columellar and parietal lamellae. Surface of all apertural barriers is finely granulated. Sinulus narrow, distinctly separated from the rest of the aperture. Umbilicus initially very narrow and suddenly widening at the last whorl. It is measuring between ½ and ¹ ⁄ 3 of the shell width. There is a deep groove running from the peristome edge towards the umbilicus along the inner side of the last whorl. This groove is terminating at the transition from the last whorl to penultimate.

Differential diagnosis.

This species superficially resembles H. circumcarinatum sp. nov. but the latter has its last whorl adnate from the penultimate, weaker barriers, narrower umbilicus, and less prominent shell sculpture. The new species is distinguished from H. khmerianum by the concrescent angular and parietal lamella as well as by the presence of spiral striation.

See under H. taehwani .

Measurements

(in mm, n = 5). SH = 2.35–2.70; SW 1 = 3.52–3.80; SW 2 = 2.08–2.18; AH = 1.32–1.62; AW = 1.40–1.79.

Etymology.

This species is named for the strong surface sculpture of its shell.

Distribution.

This species is only known from the type locality.

Remarks.

The largest, and still unexplored limestone hill in Steung Treng Province (13°47.941'N, 105°43.7671'E) was inaccessible during the collecting efforts in 2023 due to the works of a cement factory. Due to the proximity of this hill to the type locality of H. sculpturatum sp. nov., it is possible that this species can be found here as well and be threatened by quarrying.