Afrodonta geminodonta, Herbert, 2020

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, European Journal of Taxonomy 629, pp. 1-55 : 9-11

Afrodonta geminodonta sp. nov.

urn:lsid:zoobank.org:act:B6DE9D83-9082-4DEF-ABD2-0E2B48941827

Figs 1 K–N, 6, 17G–H

Diagnosis

Shell very small, spire distinctly raised; whorls weakly shouldered; protoconch microscopically shagreened; teleoconch texture silky; sculpture of simple, close-set, microscopic axial riblets; riblets alternating in strength and with even finer spiral threads in their intervals, producing a quadrate micro- reticulation; parietal region with two low, in-running ridges, upper one weaker and more deeply recessed; palatal region with 1–3 axially aligned pairs of rounded denticles recessed inside outer lip, outermost pair visible through aperture, others apparent only through translucent shell; lower denticle well below mid-whorl, upper one more or less at mid-whorl just below periphery; umbilicus relatively narrow. Shell corneous-brown to yellowish-brown when fresh; diameter up to 1.4 mm.

Etymology

From the Latin geminus: twin, and the Greek odontos (ΟΔΟντΟς): a tooth; with reference to the paired palatal dentition.

Material examined

Holotype

SOUTH AFRICA • E. Cape, Somerset East, Glen Avon Falls ; 32.67700° S, 25.63681° E; 985 m a.s.l.; 19 Jan. 2002; D.G. Herbert, M. Bursey and G. Redman leg.; in leaf-litter under bush clumps and in forest patch near base of falls; diameter 1.36 mm, height 0.73 mm; NMSA V9891/T4241 .

Paratypes

SOUTH AFRICA – E. Cape • 11 specimens; Kaboega Game Farm ; 33.26719° S, 25.42147° E; 450 m a.s.l.; 10 Mar. 2008; D.G. Herbert, L.S. Davis and M. Cole leg.; mixed woody vegetation in blind-ending kloof with stream and pools, in leaf-litter; NMSA W6248/T4243 • 16 specimens; same collection data as for holotype; NMSA P1010/T4244 • 2 specimens; Somerset East, Glen Avon Falls ; 32.67700° S, 25.63681° E; 25 Jan. 2011; M. Cole, V. Ndibo and R. Daniels leg.; ELM D17632/T170 • 1 specimen; Grahamstown, Fern Kloof ; 33.337° S, 26.537° E; ± 500 m a.s.l.; Dec. 1912; J. Farquhar leg.; NMSA V3563/T4242 .

Description

Shell very small, diameter up to 1.4 mm, H/D ratio ±0.54; spire distinctly raised; suture indented and apical portion of whorls strongly convex, whorls thus weakly shouldered; periphery somewhat above mid-whorl; whorls slightly flattened below periphery. Protoconch comprising apical cap plus approx. 0.75 whorl; diameter ±360 μm; microscopically shagreened. Teleoconch of up to 3.0 whorls; surface texture silky; sculpture of simple, close-set, microscopic axial riblets; riblets alternating in strength and with even finer spiral threads in their intervals, producing a quadrate micro-reticulation. Umbilicus deep and relatively narrow. Aperture obliquely lunate, somewhat broader basally; parietal region with two low, in-running ridges, lower one ending level with edge of aperture, upper one weaker and more deeply recessed; baso-columellar dentition lacking; palatal region with 1–3 (usually 2) axially aligned pairs of rounded denticles recessed ⅛ – ⅓ whorl behind outer lip, the outermost pair visible through aperture, the others apparent only through translucent shell; lower denticle well below mid-whorl, upper one more or less at mid-whorl just below periphery; number and position of denticle pairs somewhat variable and related to degree of development. Shell corneous-brown to yellowish-brown when fresh.

Distribution and conservation

A narrow-range endemic ( Fig. 6 ), known only from the interior of the Albany Thicket biome, north of Port Elizabeth, at altitudes of 450–1000 m; in leaf-litter of isolated patches of southern mistbelt forest. Forest patches in the Addo Elephant National Park and in nature reserves around Somerset East and Grahamstown need to be surveyed in the hope of finding extant colonies of this species in formally protected areas.

Remarks

Afrodonta geminodonta sp. nov. is characterised by its weak parietal lamellae and strong, paired palatal dentition.

Figures

Fig. 1. Shells of Afrodonta species. A–C. Af.bilamellaris Melvill & Ponsonby, 1908, Karkloof, KwaZulu- Natal, diameter 1.45 mm (NMSA W8721). D–F. Af. connollyi Solem, 1970, Middledrift, Thukela Valley, KwaZulu-Natal, diameter 1.52 mm (NMSA V4985). G–J. Af. farquhari (Burnup, 1912), Gamtoos River mouth, E. Cape, diameter 1.39 mm (NMSA W8688). K–N. Af. geminodonta sp. nov., holotype, diameter 1.36 mm (NMSA V9891/T4241).

Fig. 6. Distribution of narrow-range Afrodonta species. Af. geminodonta sp. nov. (purple triangles), Af. mystica sp. nov. (orange square), Af. pentodon sp. nov. (green circles) and Af. unilamellaris Connolly, 1933 (blue circle). Contour at 1000 m.