Diplommatina amungme, Chen, 2023

Chen, Zhe-Yu, 2023, A new species of Diplommatina Benson, 1849 (Gastropoda, Caenogastropoda: Cyclophoroidea: Diplommatinidae) from the Wollaston Expedition to New Guinea, Zootaxa 5352 (3), pp. 439-442 : 439-441

Diplommatina amungme sp. nov.

( Fig. 1 )

Diplommatina sp. Robson, 1914: 289 .

Type material. Holotype. NHMUK 1914.1 .7.395, labels: Cano Camp, 150ft, New Guinea // Dutch N. Guinea, Wollaston Exp. // Dutch New Guinea, Mimika Region, Canoe Camp of Wollaston Expedition , 150ft, 4°30’15”S, 137°20’36”E. [current geopolitical location: Kiliarma, Agimuga, Mimika Regency, Central Papua Province, Indonesia]

Etymology. The species is named after the Amungme people, an ethnic group living in the highlands of the Central Papuan, which is the type locality of the new species. Some Amungme were involved in the Wollaston Expedition as guides. The specific epithet is to be used as a noun in apposition.

Diagnosis. Diplommatina amungme sp. nov. is characterized by a reddish brown and conical shell, with the body whorl wider than above whorls, a somewhat quadrangular aperture strongly oblique, a ventrally situated columellaris and the surface reticulated due to the stronger radial ribs and weaker spiral striae.

Description. Shell small (shell height ca. 2.4 mm), dextral, reddish brown, concave conical, basal part flattened, rather thick, 6.25 slightly convex whorls; width of the lower whorls increasing evenly. Protoconch consisting of 1.5 whorls, somewhat matte; boundary between protoconch and teleoconch not clear. Teleoconch surface with fine and regularly arranged radial ribs intersecting with lower (and weaker) spiral threads (densities are approximately six ribs per 500 μm and five to six spiral lines per 200 μm on body whorl, both measured perpendicular to the structures), forming a pattern of rectangular depressions on the surface of the shell. Aperture oval to somewhat quadrangular, strongly oblique to the shell axis. Peristome single, discontinuous, expanded but not reflected, parietal callus transparent and very thin. Internal constriction distinctly presents ventrally with a thin basal radial (to the shell axis) palatal fold, corresponding surface slightly depressed. One small and slender parietal fold situated just beyond the constriction (uncertain and unable to figure, vaguely observed only through infiltrated shell). Columellar tooth emerges from aperture, downward sloping. Columellaris formed as a large, oblique, flat, and fin-like lamella near the constriction. Umbilicus open, very narrow, slitlike. Operculum unknown.

Measurement. Shell height: 2.39 mm, shell width: 1.51 mm, aperture height: 0.64 mm, aperture width: 0.92 mm (holotype).

Differential diagnosis. The “triangular” shell accompanied by the general internal structure makes it impossible to fit the new species into any known genus with great confidence. Among the sympatric genera, Palaina O. Semper, 1865 and Diancta E. von Martens, 1864 can be distinguished from the new species by containing no or only plate-like columellaris along with a sinistral shell. The new species resembles Moussonia O. Semper, 1865 species by having a dark or reddish-brown shell, rectangular surface structure and strong columellaris, but can be distinguished by its continuous aperture on the columellar side, single peristome and presenting constriction with radial palatal fold. Therefore, the new species can only be temporarily placed in Diplommatina , without affecting other monophyletic genera. This is based solely on its presenting constriction, along with a vertical palatal fold and a columellaris. Among the sympatric species, Moussonia separanda Greķe, 2017 is the most resembled one to Diplommatina amungme sp. nov. Although the shell outline and lamellar structure are significantly different, it has a blunt apex and a relatively wider lower whorl similar to the new species ( Greķe 2017). Diplommatina asynaimos Vermeulen, 1993 and D. isseli Godwin-Austen, 1889 are two species from Borneo with conical shells and flattened basal whorl, where the body whorl is wider than the whorls above it ( Vermeulen 1993). The new species can be distinguished from the former by having rounded rather than keeled whorls and from the latter by having a ventral constriction as well as the dextral shell.

Distribution. Diplommatina amungme sp. nov. is known only from the type locality.

Figures

FIGURE 1. Diplommatina amungme sp. nov., holotype. A. shell, B. internal structure observed through the translucent shell, green dotted line: constriction, white dotted line: columellaris.