Nata erugata, David G. Herbert & Adnan Mousalli, 2016

David G. Herbert & Adnan Mousalli, 2016, Revision of the dwarf cannibal snails (Nata s. l.) of southern Africa — Nata s. s. and Natella (Mollusca: Gastropoda: Rhytididae), with description of three new species, Zootaxa 4094 (1), pp. 1-67 : 41-44

publication ID	https://doi.org/ 10.11646/zootaxa.4094.1.1
publication LSID	lsid:zoobank.org:pub:E5F1E766-687D-4B00-974B-8D7939DC66A0
DOI	https://doi.org/10.5281/zenodo.5615856
persistent identifier	https://treatment.plazi.org/id/03E687FC-E025-D76C-FF1A-11FA0FFA9CC0
treatment provided by	Plazi
scientific name	Nata erugata
status	sp. nov.

Treatment

Nata erugata sp. nov.

Figures 4 View FIGURE 4 C, 6C, 29–32

Natalina caffrula — Haas, 1936: 18 (in part, Mkuzi).

Nata vernicosa — Bruggen, 1966: 376, fig. 54. Bruggen, 1969: 37. Bruggen, 1970a: 468 (in part). Bruggen, 1970b: 59. Bruggen, 1985: 286 (in part).

Etymology. From erugo (L.)—to clear of wrinkles, erugatus (L.)–without wrinkles, smooth.

Type material. Holotype ( Fig. 30 View FIGURE 30 A–C): SOUTH AFRICA: KWAZULU-NATAL: Monk’s Cowl area (29.05479°S: 29.38287°E), 1625 m, indigenous forest, in leaf-litter, F78, M. Hamer et al., 16/iii/2006 ( NMSA W5599/T3906).

Paratypes (all NMSA unless indicated otherwise): SOUTH AFRICA: KWAZULU-NATAL: Pongola Bush Nat. Res. (27.323°S: 30.4817°E), 1300 m, montane Podocarpus forest, in leaf-litter and under logs, D. Herbert & NPB, 19/i/1995 (V776/T3915, one adult and three juvenile specimens; ELM D18003/T031, one specimen); Majuba area (27.477°S: 29.685°E), 1700 m, montane Podocarpus forest, in leaf-litter, D. Herbert, 28/i/1998 (V5932/T3909, one adult and three juvenile specimens); De Beers farm, approx. 15 km NE of Van Reenen (28.30403°S: 29.50240°E), 1841 m, afrotemperate forest, in leaf-litter, A. Moussalli, D. Stuart-Fox & M. Cunningham, 9/x/2006 (W4688/ T3910, one specimen); Van Reenen (28.405°S; 29.390°E), iii/1918 (A7069/T3911, five specimens; ELM D18002/ T030, one specimen); Kranskop (28.967°S: 30.863°E), Falcon coll’n, i/1922 ( NMSA A7070/T3912, three specimens). FREE STATE: Platberg Nat. Res. (28.27631°S: 29.20772°E), 2100 m, montane shrubland/grassland, in leaf-litter, A. Moussalli, D. Stuart-Fox & M. Cunningham, 11/xii/2006 (W5621/T3908, two specimens); Golden Gate Highlands National Park (28.49430°S: 28.61868°E), 2000 m, gully thicket/grassland, buried in shrubs, A. Moussalli & D. Stuart-Fox, 28/xii/2005 (W4243/T3913, one specimen); Zastron area, Mapaya Hill (30.27439°S: 27.21902°E), ~ 1860 m, in soil amongst boulders in narrow, shaded cleft above sandstone cliff, st'n 08-059, D. Herbert & L. Davis, 22/xi/2008 (W6573/T3907, three specimens). E. CAPE: Witteberge, Balloch farm, north of Barkly East (30.71255°S: 27.69507°E), Lesotho highland grassland, under rock, D. Stuart-Fox, 1/iv/2005 (W4836/ T3914, one adult and two juvenile specimens).

Additional material examined: See Appendix 4.

Identification. Differs from Nata vernicosa in that the apical surface is almost completely devoid of regular, close-set, axial riblets; although axial sculpture remains, it is present only in the form of weak, irregularly spaced growth-lines. More similar to Nata watsoni sp. nov., but that species has very different radula morphology and occurs in a different region and biome (Albany Thicket).

Shell ( Fig. 30 View FIGURE 30 ): Lenticular, occasionally discoidal; whorls comparatively shallow and spire often low; largest specimens comprising 3.25–3.5 teleoconch whorls; periphery at or more usually slightly below mid-whorl; suture above periphery, at most weakly descendant prior to aperture. Protoconch diameter 1.0– 1.9 mm, comprising ±1.0 whorl, smooth and glossy, junction with teleoconch usually rather weakly defined. Apical surface of teleoconch smooth and glossy, lacking regular axial riblets and sculptured only by weak growth irregularities; these strongest below suture, weakest at periphery and on base; no significant spiral sculpture, but some specimens with faint traces of vermiform wrinkles in places. Base and umbilical margin evenly rounded; umbilicus of moderate width, steep-sided; growth-lines slightly stronger within umbilicus. Aperture roundly or distinctly ovate, often obliquely descendant ( Fig. 30 View FIGURE 30 J); peristome interrupted by bulging parietal region; outer lip thin with membranous periostracal fringe (commonly lost); outer lip shallowly sinuous when undamaged; upper part of columella lip extending forward and slightly reflected.

Shell translucent milky-white when fresh; periostracum glossy, pale yellowish-brown to honey-gold, commonly with some axial variation in intensity, producing unevenly spaced, slightly darker axial banding, but this generally weak.

Dimensions: Holotype, diameter 15.5 mm, height 8.1 mm; largest specimen, diameter 21.0 mm, height 11.4 mm; H:D of adults 0.46–0.60 [N=34].

Living animal ( Figs 4 View FIGURE 4 C, 31): Body generally pale; head and neck greyish-white to cream, dorsal region of neck sometimes pale grey or pale bluish-grey; optic tentacles a slightly darker shade of grey; foot paler beneath shell; posterior portion of foot relatively short; some individuals with microscopic orange pigment granules in skin, particularly on hind end of foot; skin texture moderately well defined; mantle edge pale, also with minute orange granules in some individuals; lining of mantle cavity with little or no dark pigmentation, except for a diffuse blackish mark just inside pneumostome, visible through shell; kidney trigonal, pale buff, not conspicuous through shell.

Radula ( Figs 6 View FIGURE 6 C, 32): Very similar to that of Nata vernicosa , but usually with fewer lateral teeth. Formula 0+(7–8)+(3–4); length up to 12.0 mm, with 24–33 V-shaped rows of teeth; teeth progressively larger from anterior to posterior of radula; rachidian absent; largest tooth (number 7 or 8) taken to be outermost lateral. Tooth morphology as in N. vernicosa .

Distal genitalia: As in Nata vernicosa . Epiphallus enters penis between one-third and two-thirds length of the latter from its base; internally, lining of penis forms a raised rim around epiphallus pore; basal portion of bursa copulatrix duct swollen (particularly so in specimens from Hogsback), tapering to mid region and evenly slender thereafter, but constricted prior to bursa copulatrix which is small, subovate to reniform and thin walled.

Distribution ( Fig. 29 View FIGURE 29 ): Endemic to eastern South Africa and southern Mozambique, but relatively widely distributed within this region, ranging from Hogsback in the south west, through western Lesotho, eastern Free State and Gauteng, into western and northern KwaZulu-Natal, the Lowveld of Mpumalanga and southern Mozambique. Throughout the southern and western parts of its range the species is largely restricted to altitudes over 1000 m and extending to 2200 m along the KwaZulu-Natal escarpment edge. However, the populations in north-eastern KwaZulu-Natal (Zululand), the Mpumalanga Lowveld (southern Kruger National Park) and Mozambique occur at much lower altitudes (30–300 m).

Habitat. At altitudes above 1000 m the species occurs primarily in afrotemperate forest and more thickly vegetated habitats such as Leucosidea scrub. However, specimens have also been found in sheltering microhabitats in more open vegetation, even montane grassland. At lower altitudes in Zululand and the Kruger National Park it occurs in a variety of vegetation types within the Savannah Biome.

Remarks. When discussing Pfeiffer’s ‘ var. minor ’, Connolly (1939) noted that although Pfeiffer’s description ‘ costulis superficiei obsoletioribus ’ (Pfeiffer 1853: 95) may apply to an immature example of Nata liparoxantha , ‘…there extends from the Cape Province to Delagoa a hitherto undetermined race, which may represent his variety. It differs from vernicosa solely in being very much smoother, the sculpture consisting of fine growth striolae instead of costulae’ ( Connolly 1939: 100). We have likewise been able to discern such a ‘race’, but we do not consider that it can be considered conspecific with Pfeiffer’s var. minor . Examination of the lectotype of the latter at the SMNH (see above regarding its authenticity) reveals that although the axial sculpture is weak, distinct and regularly spaced axial riblets are nonetheless present on the adapical surface and the specimen is simply a weakly sculptured example of the variable N. vernicosa . Since all the other names currently considered to be junior synonyms of N. vernicosa likewise relate to material with distinct axial riblets, we are therefore obliged to propose a new name for the present material.

Throughout much of its distribution Nata erugata sp. nov. is the only species of Nata to be found, but at the lower limits of its altitudinal range, particularly in E. Cape and KwaZulu-Natal, there is some geographical overlap with Nata vernicosa ( Fig. 29 View FIGURE 29 ). However, further studies are needed to establish whether and to what extent the two species co-occur. There is certainly evidence that this may be the case at some localities (Hogsback, Umthatha area, Karkloof and Pilgrim’s Rest area).

The occurrence of populations of what is largely a higher altitude species in the hotter more low-lying regions of northern KwaZulu-Natal, the Kruger National Park and southern Mozambique ( Fig. 29 View FIGURE 29 ), at altitudes of well below 1000 m, is anomalous and hard to explain. It is certainly suggestive of there being a further cryptic lineage in what we group under one species. For this reason, we have not included any specimens from these localities in the type material for this species. This is an issue needing to be studied in more detail using molecular data.

Conservation. As interpreted here, Nata erugata sp. nov. is a widespread and moderately common species occurring in a range of habitat types. As such, its conservation is not at present a matter of concern.