Phialodonta atromontana Herbert 2020, gen. et sp. nov.
Creators: name: Herbert, David G.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Charopidae
Phialodonta
Phialodonta atromontana

description: Phialodonta atromontana gen. et sp. nov.
urn:lsid:zoobank.org:act: 4A34E0A1-99C9-4892-83DC-080F239C0921
Figs 14, 15 E–H, 19C–D
Diagnosis
Shell very small, spire slightly raised; protoconch lacking axial sculpture; teleoconch sculpture of curved, close-set, compound, axial riblets, with 4–5 finer, intermediary axial threads; spiral sculpture of extremely fine, close-set threads; aperture with a low, rounded, in-running parietal ridge, lacking basocolumellar dentition; palatal region with two pairs of close-set, spirally aligned denticles, one pair close to mid-whorl, the other basal; umbilicus wide. Shell pale corneous-brown to honey-brown; diameter up to 1.4 mm.
Etymology
From the Latin ater: black, and mons: a mountain; with reference to the Groot Swartberg range.
Material examined
Holotype SOUTH AFRICA • W. Cape, Calitzdorp area, Matjiesvlei; 33.44525° S, 21.65388° E; 360 m a.s.l.; 4 Nov. 2013; D.G. Herbert, L.S. Davis, M. and K. Cole leg.; rocky hillside with succulents and aloes, in leaf-litter; diameter 1.4 mm, height 0.61 mm; NMSA W9580/T4254.
Paratypes SOUTH AFRICA • 7 specimens; same collection data as for holotype; NMSA P1016/T4255.
Description
Shell very small, diameter up to 1.4 mm, H/D ratio ±0.43; spire slightly raised; whorls tightly coiled, relatively narrow; last adult whorl descending slightly below penultimate whorl; suture narrowly indented, periphery evenly convex. Protoconch comprising apical cap plus approx. 0.67 whorl; diameter ±410 μm; smooth to microscopically shagreened, lacking axial sculpture. Teleoconch of up to 2.25 whorls; sculptured by distinct, curved, close-set, compound axial riblets, with 4–5 finer, uneven, intermediary axial threads; intervals between riblets approx. twice riblet width at whorl periphery; spiral sculpture of extremely fine, close-set threads more or less throughout. Umbilicus wide. Aperture broadly lunate to almost D-shaped; parietal region with a low, rounded, in-running ridge just below mid-whorl; baso-columellar region lacking dentition; palatal region with two pairs of close-set, spirally aligned denticles, one pair close to mid-whorl, the other basal. Shell pale corneous-brown to honey-brown, usually encrusted with soil particles.
Distribution and conservation
A narrow-range endemic (Fig. 14), known only from the southern edge of the Groot Swartberge in the region of Calitzdorp, at 360 m a.s.l.; in accumulations of leaf-litter in sheltered microhabitats within Gamka Thicket. The type locality lies close to the protected Klein Swartberg Mountain Catchment Area and there are also several private and provincial nature reserves in the vicinity. Further sites in these areas need to be surveyed in the hope of finding additional extant colonies of the species.
Remarks
Conchologically closest to Phialodonta aviana gen. et sp. nov. and P. rivalalea gen. et sp. nov., but differs in the form of the palatal dentition. In specimens at intermediate growth stages the palatal denticles may be single rather than paired, or even totally absent.
description: Published as part of Herbert, David G., 2020, Revision of the aperturally dentate Charopidae (Gastropoda: Stylommatophora) of southern Africa - genus Afrodonta s. lat., with description of five new genera, twelve new species and one new subspecies, pp. 1-55 in European Journal of Taxonomy 629 on pages 40-41, DOI: 10.5852/ejt.2020.629, http://zenodo.org/record/3762280