Selatodryas, Herbert, 2017

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 : 32-33

Genus Selatodryas gen. nov.

urn:lsid:zoobank.org:act:72AF5C89-20EB-44EE-B2F5-6390BD6E0183

Type species

Selatodryas roseosoma gen. et sp. nov.

Diagnosis

Shell small, delicate and glossy, periphery at or just below mid-whorl; umbilicus absent, edge of columella lip reflected and slightly thickened with a thin, whitish callus; columella running into axis of coiling rather than fusing with the parietal region; protoconch essentially smooth. Optic tentacles conspicuously dark. Penis long, coiled inside sheath; epiphallus long; caecum elongate, situated just proximal to mid-point of epiphallus, well separated from insertion of penial retractor muscle; penial verge absent; vagina long. Terminal branches of spermatophore spines bluntly bifid; distal portion of spermatophore tail smooth and relatively short.

Etymology

From the Greek ‘σελάτης’, m., a snail, and ‘Δρυάς’, f., a Dryad or forest nymph; in reference to the delicate shell and preferred habitat of these snails. Gender feminine.

Remarks

The morphology of the penis and epiphallus, and the bluntly bifid branch tips of the spermatophore spines of Selatodryas gen. nov. suggest a close relationship with Sheldonia s.s. Similarly, the form of the columella region (complete absence of an umbilicus) is a character shared with some species of Sheldonia s.s. (such as S. trotteriana (Benson, 1848) , S. natalensis (Pfeiffer, 1846) and S. cotyledonis (Benson, 1850)) . However, two characters of Selatodryas gen. nov. set the genus apart from Sheldonia s.s., namely the smooth protoconch and the short distal portion of the spermatophore tail that lacks a double row of blunt projections.

Preliminary mtDNA data confirm this close relationship, placing the two species of Selatodryas gen. nov. in a well-supported clade sister to, but distinct from Sheldonia s.s. ( Herbert & Moussalli 2009). Selatodryas gen. nov. is known only from high altitude forest (Southern Mistbelt). From a biogeographical perspective the ranges of the two genera do not overlap. Sheldonia s.s. occurs over a large part of the Eastern and Western Cape, from the Mbhashe River valley west to St Helena Bay, whereas Selatodryas gen. nov. occurs as an almost parapatric isolate to the north-east of Sheldonia s.s., suggesting that Selatodryas gen. nov. diverged from the ancestral Sheldonia stock before Sheldonia s.s. radiated into the drier regions of the southern Cape and Karoo.

The two species of Selatodryas gen. nov. described below differ conspicuously in body coloration and this is reflected in their respective species names. However, the taxonomic value of body colour as a diagnostic character in southern African urocyclid snails must be viewed with caution. A number of species show considerable intra-specific variation in this regard, including Kerkophorus terrestris sp. nov. described above ( Fig. 17 ), as well as Sheldonia monsmaripi Herbert, 2016 and S. natalensis (Pfeiffer, 1846) . Such colour differences may relate to ecological rather than genetic factors. The above notwithstanding, in the two species of Selatodryas gen. nov. the colour difference is pronounced and geographically consistent, and there are further correlated differences in genital anatomy and spermatophore morphology, providing confirmatory evidence that the two are distinct species.

Figures

Fig. 17. Kerkophorus terrestris sp. nov., living animals. A. Collywobbles, E Cape, shell diameter 13.1 mm (holotype, NMSA W3979/T3862). B. Mount Thesiger, Port St Johns, E Cape, shell diameter 10.7 mm (paratype, NMSA V6515/T3859).