Costulodonta pluridens, 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 : 32-34

Costulodonta pluridens gen. et sp. nov.

urn:lsid:zoobank.org:act:46373BEE-D1E5-4F91-BA68-BC4B320DA462

Figs 11 , 12 A–D, 18O–P

Diagnosis

Shell small, spire flat or at most slightly raised; protoconch with close-set axial riblets; teleoconch sculpture of close-set, compound axial riblets and microscopic spiral threads; aperture with two rounded, in-running parietal lamellae, the lower one stronger, and a well-developed, in-running, ridge-like basocolumellar denticle; palatal region with four denticles recessed approx. ⅛ whorl behind outer lip. Shell translucent, corneous-brown to pale honey-brown when fresh; diameter up to 1.8 mm.

Etymology

From the Latin plus: more, and dens: tooth; with reference to the many apertural teeth.

Material examined

Holotype

SOUTH AFRICA • KwaZulu-Natal, Utrecht area, Groenvlei, Guquka Hill (Arrarat Farm); 27.39° S, 30.34° E; 1700 m a.s.l.; 28 Jan. 1998; D.G. Herbert leg.; montane Podocarpus forest, in leaf-litter; diameter 1.8 mm, height 0.9 mm; NMSA V5920 /T4267.

Paratypes

SOUTH AFRICA • 8 specimens; same collection data as for holotype; NMSA P1019/T4268 • 6 specimens; same collection data as for holotype; montane Podocarpus forest, in moss on tree trunk; NMSA V6287 /T4269 .

Other material

SOUTH AFRICA – KwaZulu-Natal • 1 specimen; Utrecht area, Bivane River catchment, Elandsnek , east of Pivaans Waterval Farm ; 27.460° S, 30.421° E; 1850 m a.s.l.; 1 Dec. 1999; D.G. Herbert leg.; small patch of montane Podocarpus forest, in leaf-litter; NMSA V7564 • 1 specimen; same collection data as for preceding; NMSA V7581 .

Description

Shell small, diameter up to 1.8 mm, H/D ratio ±0.50; spire flat or at most slightly raised; whorls tightly coiled; last adult whorl very slightly descendant; suture indented, periphery evenly convex. Protoconch comprising apical cap plus approx. 0.75–1.0 whorl; diameter ±365 μm; initially smooth, but for the most part sculptured by close-set axial riblets, with indistinct traces of irregular spiral threads. Teleoconch of up to 3.25 whorls; sculptured by distinct, close-set, compound axial riblets with 3–4 finer, uneven, intermediary axial threads; intervals between riblets 1–2 times riblet width at whorl periphery; spiral sculpture of microscopic threads more or less throughout, 1–2 stronger threads below suture (visible only under SEM). Umbilicus relatively wide. Aperture lunate, broader basally; parietal region with two rounded, in-running lamellae, the lower one stronger and projecting slightly beyond aperture; baso-columellar region with a well-developed, in-running, ridge-like denticle; palatal region with four denticles recessed approx. ⅛ whorl behind outer lip, shape of denticles somewhat variable, the two below mid-whorl usually elongate, the one just above mid-whorl often more rounded, the fourth is subsutural and very small. Shell translucent, corneous-brown to pale honey-brown when fresh.

Distribution and conservation

A narrow-range endemic ( Fig. 11 ), known only from the escarpment north of Utrecht, KwaZulu-Natal, at 1700–1850 m; northern afrotemperate forest, in leaf-litter and amongst epiphytic moss on tree trunks. The neighbouring Paardeplats, Pongola Bush and Tafelkop nature reserves need to be surveyed in the hope of finding extant colonies of this species in formally protected areas.

Remarks

The relatively complex apertural dentition of Costulodonta pluridens gen. et sp. nov. renders it easily separated from other species of Costulodonta gen. nov.

Figures

Fig. 11. Distribution of Costulodonta gen. nov. species. C. acinaces (Connolly, 1933) gen. et comb. nov. (green square), C. bidens gen. et sp. nov. (turquoise squares), C. burnupi (Connolly, 1933) gen. et comb. nov. (orange square) C. pluridens gen. et sp. nov. (pink squares), C. trilamellaris (Melvill & Ponsonby, 1908) gen. et comb. nov. (royal blue square). Contour at 1000 m.

Fig. 12. Shells of Costulodonta gen. nov. species. A–D. C. pluridens gen. et sp. nov., holotype, diameter 1.8 mm (NMSA V5920/T4267). E–G. C. trilamellaris (Melvill & Ponsonby, 1908) gen. et comb. nov., paralectotype, Dargle, KwaZulu-Natal, diameter 1.45 mm (NMSA 2181/T624).