Hypselostoma aenigma Gojšina, Grego & Páll-Gergely, 2025

Hypselostoma aenigma Gojšina, Grego & Páll-Gergely sp. nov.

Figs 111 B View Figure 111 , 114 View Figure 114 , 115 View Figure 115 , 158 View Figure 158

Type material.

Holotype. Myanmar • 1 shell (SH: 2.1 mm; SW: 1.7 mm); Kayin State, Kamarmaung, Phon Tho Village, Pan Do Mi Mountain spring cave at W foot of the mountain; 17°19.3575'N, 97°43.4842'E 19. May 2019; J. Grego leg; CUMZ 14452 View Materials . GoogleMaps

Type locality.

Myanmar, Kayin State, Kamarmaung, Phon Tho Village, Pan Do Mi Mountain spring cave at W foot of the mountain; 17°19.3575'N, 97°43.4842'E.

Diagnosis.

Hypselostoma species with conical-ovoid shell, spirally striated whorls, and the last whorl with a keel below the centre of the periphery. Apertural barriers three but the parietal lamella is the only tooth-like barrier. Palatal plica and columellar lamella are present as swellings on the peristome.

Description.

Shell conical-ovoid, pale yellowish, consisting of nearly 4.5 whorls separated by a deep suture. All whorls, except the last one, regularly rounded and convex. Last whorl with a blunt keel below the centre of the periphery and weakly concave to almost flat whorl outline both above and below the keel. Protoconch of same colour as the rest of the shell, finely pitted showing spiralling pattern which continues as more distinct spiral striae terminally. It consists of ~ 1.75 whorls. Teleoconch coarsely sculptured with irregularly spaced radial growth lines but also with dense spiral striae. Spacing between the two spiral striae equals the width of two or three striae. Last whorl adnate to the penultimate and very slightly ascending (~ 7 ° compared to the shell axis), making the apertural profile weakly opisthocline to the shell axis. Peristome white, thick, and expanded (especially on the parietal side) but not reflected. Apertural barriers largely reduced and of very unusual appearance for any hypselostomatid. Parietal lamella is the only „ tooth-like “ barrier in the aperture but it is very low and short. Palatal plica and columellar lamella not present in their typical forms but rather as very weak and indistinct swellings on the peristome, visible only in the frontal view. These swellings are probably homologous to the two mentioned barriers. There are no other barriers in the aperture. Surface of all apertural barriers is very finely granulated (almost smooth). Sinulus wide due to the weak parietal lamella and palatal plica. Umbilicus extremely narrow, dot like and slightly elongated. Umbilical groove absent.

Differential diagnosis.

This species is not similar to any other congener or species within other genera due to the unique appearance of apertural barriers.

Measurements

(in mm, n = 1): SH = 2.1; SW = 1.7; AH = 0.97; AW = 0.93.

Etymology.

The specific epithet aenigma comes from a Latin word for a riddle (which refers to the unique appearance of the shell and unclear relationship with other congeners) and is to be used as a noun in apposition.

Distribution.

This species is known only from its type locality.