Microkerkus Godwin-Austen, 1912

Herbert, David G., 2017, A new genus and eight new species of tail-wagger snails from eastern South Africa, with a key to genera within Sheldonia s. l. (Gastropoda: Urocyclidae), European Journal of Taxonomy 309, pp. 1-50 : 28

Genus Microkerkus Godwin-Austen, 1912

Microkerkus Godwin-Austen, 1912a: 128 .

Type species Helix symmetrica Craven, 1880 , by subsequent designation ( Connolly 1912: 111).

Remarks

Watson (1934), Connolly (1939) and Zilch (1959 –60) treated Microkerkus as a synonym of Kerkophorus , a conclusion justified by the minimal diagnosis provided by Godwin-Austen (1912a). However, there are consistent differences in the morphology of the male distal genitalia of Microkerkus that clearly set it apart from Kerkophorus and other members of Sheldonia s.l. Specifically, the epiphallus is generally longer, the caecum is small, globose rather than elongate, and it is situated more or less in the middle of the epiphallus, rather than adjacent to the penial retractor muscle. Furthermore, the tail of the spermatophore is bifid, comprising a spinose element and a secondary smooth element that branches from it. In terms of the relative length of the two elements of the spermatophore tail, Microkerkus appears divisible into two groups. Typically, after the bifurcation the smooth element is much longer than the spinose element ( M. symmetricus , M. maseruensis (Connolly, 1929) and M. arnotti (Benson, 1864)) , but in others the two elements, after splitting, are more or less equal in length ( M. burnupi ( Godwin-Austen, 1914) , M. leucospira (Pfeiffer, 1857) and M. pondoensis Godwin-Austen, 1912 ). This difference is also evident in the morphology of the flagellum, the latter group having a clearly bifid flagellum. (The figure of the genitalia of M. symmetricus given by Godwin-Austen (1914: pl. 19, fig. 2) is almost certainly misidentified and in fact represent a species of Kerkophorus .)

Shell morphology is variable; the shell surface may be lustreless or glossy, the protoconch smooth or spirally lirate, but always lacks punctations; the umbilicus may be relatively broad, narrowly rimate or absent; the coloration is usually uniform, though the apical whorls may be paler, and there is never a brown peripheral spiral band.