Gulella libertas, Cole & Herbert, 2023

Cole, Mary L. & Herbert, David G., 2023, Seven new narrowly endemic species of Gulella Pfeiffer, 1856 from eastern South Africa (Gastropoda, Streptaxidae) and status revision for another, European Journal of Taxonomy 900 (1), pp. 1-31 : 24-26

Gulella libertas sp. nov.

urn:lsid:zoobank.org:act:54F995CA-0DA3-4D6F-8566-7207A1209EA3

Figs 9 , 12

Diagnosis

Shell minute, sub-cylindrical; sculptured with weak widely-spaced axial ribs; dentition seven-fold, including an angular parietal lamella, a large, bicuspid labral tooth, the lower cusp stronger, a low, deeply inset transverse basal tooth slightly to right of centre, an in-running tooth at base of columella lip, a prominent tooth in middle of columella lip and a large, convex columella lamella; peristome protruding at position of labral and superficial columella teeth; umbilicus widely open, more or less circular.

Etymology

From Latin ‘ libertas ’ meaning ‘freedom’. The type locality is in the town Vryheid, Afrikaans for freedom, an area with a history of battles.

Type material

Holotype SOUTH AFRICA – KwaZulu-Natal • Vryheid, indigenous forest behind Lancaster Lodge ; 27.7507° S, 30.7624° E; 1140 m a.s.l.; 14 Dec. 2012; A. Ndaba, B. Mkhize and G. Zamisa leg.; sorted from leaf-litter; NMSA W9287 /T4601.

Paratypes SOUTH AFRICA – KwaZulu-Natal • 2 specs; same collection data as for holotype; NMSA-Mol 0P2352/T4602 • 1 spec.; same collection data as for holotype; ELMD 19090/T245, ex NMSA W9287 • 1 spec.; same collection data as for holotype; NHMUK 20230172 , ex NMSA W9287 .

Other material examined

SOUTH AFRICA – KwaZulu-Natal • 2 specs (1 adult, 1 juvenile); same collection data as for holotype; NMSA-Mol 0P2353 .

Description

SHELL ( Fig. 12 ). Shell minute, sub-cylindrical, length 2.2–2.7 mm, width 1.1–1.2 mm, L:W 2.03–2.29 (n = 6). Protoconch approx. 0.7 mm in diameter, comprising 2.25 whorls, smooth ( Fig. 12A–B ); junction between protoconch and teleoconch distinct.Teleoconch comprising approx. 5 whorls; first whorl convex, others weakly so; first 0.25 whorl with fine, closely spaced riblets, remainder with widely-spaced axial ribs, strong below suture and fading out before reaching next suture except on body whorl ( Fig. 12A–B ). Peristome very thick and reflected. Aperture more or less quadrate, base rounded; apertural dentition seven-fold ( Fig. 12C ): 1) an angular parietal lamella, with an oblique ridge extending from angle to middle of parietal region, almost forming a buttress, side of lamella facing labral sinus concave, running into aperture medial to angle, 2–3) two labral teeth fused to form a large plate, the lower tooth stronger, 4) a low, inset transverse basal tooth slightly to right of centre, 5) an in-running, ridge-like basal tooth well to left of centre beginning at base of columella lip, 6) a prominent tooth in middle of columella lip and 7) a large, broadly rounded columella lamella. A weak ridge appears to join the tooth on columella lip and columella lamella in some specimens. Labral tooth corresponds with a deep pit behind outer lip ( Fig. 12B ). When viewed from either side, profile of aperture juts out in position of teeth on labrum and columella lip, which lie opposite each other. Umbilicus widely open, more or less circular, approx. 0.12 mm in diameter ( Fig. 12D ). Tooth in middle of columella lip corresponds with an elongated pit behind columella lip which joins the umbilicus ( Fig. 12D ). Shell translucent when fresh, red-orange coloration of dried tissue of animal visible internally.

Distribution ( Fig. 9 )

Known only from the outskirts of the town of Vryheid in north-central KwaZulu-Natal, at approx. 1140 m above sea level.

Habitat

Northern Afrotemperate Forest ( Mucina & Geldenhuys 2006).

Remarks

Gulella libertas sp. nov. resembles Gulella melvilli (Burnup, 1914) , an uncommon species widely distributed in the interior of KwaZulu-Natal. The major differences are that the axial ribs of G. libertas are stronger, rendering the subsutural region crenulate, and there is a prominent tooth in the middle of the columella lip. Gulella sylvia (Melvill & Ponsonby, 1903) from the Eastern Cape has similar apertural dentition, but it is smooth and has a bicuspid columella lamella.

Conservation

Gulella libertas sp. nov. appears to be a very rare species, known only from the type locality, which is not within a formally protected area. A local, municipal nature reserve, Vryheid Hill Nature Reserve, is nearby and it is likely that the species also occurs there.

Figures

Fig. 9. Distribution map of Gulella hlathikhulu sp. nov. (green circles), G. nkandla sp. nov. (yellow triangles), G. mystica sp. nov. (red squares) and G. libertas sp. nov. (blue circle) in north-central KwaZulu-Natal. Contours at 1000 m and 2000 m.

Fig. 12. Gulella libertas sp. nov., holotype (NMSA W9287/T4601), length 2.6 mm, width 1.2 mm. A. Aperture view. B. Side view. C. Detail of aperture. D. Oblique view of base showing umbilicus.