Afrocyclus, Cole, 2019

Cole, Mary L., 2019, Revision of Chondrocyclus s. l. (Mollusca: Cyclophoridae), with description of a new genus and twelve new species, European Journal of Taxonomy 569, pp. 1-92 : 60-61

Genus Afrocyclus gen. nov.

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Type species

Afrocyclus isipingoensis ( Sturany, 1898) gen. et comb. nov.

Diagnosis

Shell dextral, small, depressed; aperture circular, last whorl descending near aperture, peristome not thickened, continuous and free; umbilicus wide and deep, exposing all the whorls; periostracum glossy and lacquer-like with lamellate axial costae at regular intervals, usually expanded into spiral rows of hairs; operculum duplex, corneous; inner portion consists of a thin disc which grows outwards in a tight spiral, smooth on inside where it attaches to foot; fused to disc on its outer surface is a multispiral, elevated horny blade-like lamella formed by fused bristles; a fringe of fused bristles emanates from outer surface of each lamellar whorl; radula taenioglossate, two large cusps on second lateral tooth; penis lies dorsally immediately behind right tentacle and consists of a stout, muscular, cylindrical shaft, wrinkled along most of its length due to annular rugae, and a terminal, tapering intromittent organ without flagellum; seminal tube completely enclosed without seminal groove.

Etymology

The specific name is derived from ‘Africa’ and refers to its Afromontane occurrence.

Remarks

mtDNA data clarified that Afrocyclus gen. nov. constituted a radiation distinct from that of Chondrocyclus s.s. ( Cole et al. 2019). Specimens of Afrocyclus gen. nov. can in most cases be recognised at a glance on morphological grounds, being very small, very depressed (the apex can even be concave), discoid shells with spiral rows of hairs projecting from the axial costae. This morphotype is widely distributed in latitude and altitude, occupying isolated Afromontane forest patches along the Great Escarpment from northern South Africa (Limpopo province, 23° S) to the Eastern Cape (32.7°S) and extending to the coast ( Fig. 2 ). mtDNA data showed that what was previously lumped as Afrocyclus isipingoensis gen. et comb. nov. is a species complex, and within it, external morphology is relatively conserved, making it difficult to distinguish taxa by morphology alone. A. exsertus gen. et comb. nov., which occupies a narrow zone on the east coast, is strikingly different morphologically, bearing no hairs and with the axial lamellae only slightly expanded around the periphery. The operculum of the latter also deviates dramatically from the flat, fragile operculum of most specimens of Afrocyclus gen. nov. and is more robust with a rigid fringe consisting of bunches of short bristles. Phylogenetic relationships within Afrocyclus gen. nov. are not fully resolved and further molecular and morphological data from throughout its range are required to revise this complex.

Key to species of Afrocyclus gen. nov.

1. Axial lamellae slightly expanded at periphery, but not produced into hairs........................................ ............................................................... A. exsertus ( Melvill & Ponsonby, 1903) gen. et comb. nov.

– Axial lamellae expanded into multiple spiral rows of hairs .............................................................. 2

2. Spiral rows of periostracal hairs include a row of very short hairs immediately below suture on body whorl .................................................................. A. isipingoensis ( Sturany, 1898) gen. et comb. nov.

– No spiral row of very short periostracal hairs immediately below suture......................................... 3

3. Three spiral rows of hairs at periphery; upper edge of rachidian tooth smooth .................................. .................................................................................................................. A. oxygala gen. et sp. nov.

– More than three spiral rows of hairs on body whorl; upper edge of rachidian tooth serrated........... 4

4. Protoconch strongly malleate ...................................................................... A. potteri gen. et sp. nov.

– Protoconch malleate, but not strongly .......................................................... A. bhaca gen. et sp. nov.

Figures

Fig. 2. Map of South Africa showing distribution of the five major clades of Chondrocyclus s.l. Ancey, 1898. Provinces with records of Chondrocyclus are labelled.