Afrodonta bilamellaris Melvill & Ponsonby, 1908

Afrodonta bilamellaris Melvill & Ponsonby, 1908 View in CoL

Figs 1 View Fig A–C, 2, 17A–B

Afrodonta bilamellaris Melvill & Ponsonby, 1908: 134 View in CoL , pl. 7, fig. 6.

Afrodonta bilamellaris londonensis Solem, 1970: 359 View in CoL , fig. 2c–d. Syn. nov.

Afrodonta bilamellaris View in CoL – Godwin-Austen, in Melvill & Ponsonby 1908: 135. — Connolly 1939: 251, text-fig. 19 (1). — Herbert & Kilburn 2004: 249, text-fig.

Endodonta [Endodonta (Afrodonta)] bilamellaris – Burnup 1912: 335, pl. 24, fig. 18.

Endodonta (Afrodonta) bilamellaris – Connolly 1912: 127.

Afrodonta bilamellaris bilamellaris View in CoL – Solem 1970: 358, fig. 2a–b.

Diagnosis

Shell small, spire slightly raised, whorls slightly flat-sided; protoconch smooth, at most microscopically shagreened (diameter ±315 μm); teleoconch texture silky; sculpture comprising simple, very fine and close-set axial riblets, tending to alternate in strength; spiral sculpture of faint threads in riblet intervals; parietal region with a single well-developed, in-running lamella (sometimes bifurcating posteriorly); baso-columellar region with a well-developed, in-running ridge-like denticle; palatal region usually lacking dentition (exceptionally with a weak supra-peripheral ridge); umbilicus relatively narrow. Shell pale honey-coloured when fresh; diameter up to 1.7 mm.

Distribution and conservation

Endemic to south-eastern South Africa ( Fig. 2 View Fig ), ranging widely from central KwaZulu-Natal (Zinkwazi), through E. Cape to eastern W. Cape (Knysna area); in E. Cape and W. Cape it is confined to forests in the coastal hinterland, but in KwaZulu-Natal it ranges inland to the southern mistbelt forests of the Midlands. Inhabits a range of forest and dense thicket-like habitats, from the coast to 1500 m a.s.l., living in leaf-litter. Not of conservation concern.

Remarks

Solem (1970) described smaller, strongly dentate specimens from East London as a separate subspecies, Afrodonta bilamellaris londonensis , and similar specimens have been found subsequently at other localities (Port St Johns area, Tsitsikamma and Knysna). However, the reported differences between the subspecies are a matter of degree and I have not found it possible to discriminate consistently between the two. This, in conjunction with the fact that the records of strongly dentate londonensis specimens are not geographically circumscribed and spatially separated from the nominotypical form, leads me to conclude that the two do not represent distinct entities and that Af. bilamellaris is simply a variable species in terms of the strength of the apertural dentition. This variation occurs to some extent within as well as between populations. In one strongly dentate londonensis population from the Port St Johns area, some individuals evince traces of palatal dentition in the form of a weak supra-peripheral ridge or denticle and occasionally an even weaker sub-peripheral one.