Gulella crookesi, Cole & Herbert, 2022

Cole, Mary L. & Herbert, David G., 2022, Eight new species of Gulella Pfeiffer, 1856 from the south-east coast of South Africa (Gastropoda: Streptaxidae), European Journal of Taxonomy 813, pp. 1-32 : 17-18

Gulella crookesi sp. nov.

urn:lsid:zoobank.org:act:DFA049BF-A8B0-4B47-B04C-E6EB64CEE8F0

Figs 2 , 7A–D

Diagnosis

Shell minute, sub-cylindrical; smooth and glossy; aperture markedly constricted by teeth and narrower towards base; apertural dentition nine-fold, including an oblique parietal lamella with a notch in its lower margin, a large triangular labral tooth, its upper margin sinuous, and with a denticle near lip edge and another further into aperture, three inset basal teeth in close apposition, a low, broad rounded denticle on columella lip and a large inset tricuspid columella lamella; umbilicus widely open and with distinct peri-umbilical pleats.

Etymology

Named for the type locality, the Vernon Crookes Nature Reserve, KwaZulu-Natal.

Material examined

Holotype SOUTH AFRICA – KwaZulu-Natal • Vernon Crookes Nature Reserve , 13.5 km WNW of Scottburgh, scarp forest ; 30.2728° S, 30.6052°E, 410 m a.s.l.; 12 Jan. 2010; M. and K. Cole leg.; NMSA P1680/ T4526 , prev. ELMD 16438.

Paratypes SOUTH AFRICA – KwaZulu-Natal • 1 spec.; same collection data as for holotype; NMSA P1617/ T4499 , prev. ELMD 16438 • 4 specs.; same collection data as for holotype; ELMD 16438/T 230 • 2 specs.; same collection data as for holotype; NHMUK 20210071 , prev. ELMD 16438 • 2 specs.; same collection data as for holotype; NMW.Z.2021.011.00003 , prev. ELMD 16438 • 1 spec.; same collection data as for holotype; RMNH.MOL.452590 , prev. ELMD 16438 • 1 spec.; same locality as for holotype, Station 11-14 ; 15 April 2011; D. Herbert, L, Davis, M. Cole and R. Daniels leg.; NMSA W8095/T4484 .

Description

SHELL ( Fig. 7 ). Shell minute, sub-cylindrical to squat, length 2.4–2.6 mm, width 1.1–1.2 mm, L:W 2.0–2.2 (n = 7). Protoconch approx. 0.9 mm in diameter, comprising approx. 2.5 whorls, smooth; junction between protoconch and teleoconch not distinct. Teleoconch comprising approx. 4 whorls; whorls weakly convex; smooth and glossy but with fine growth lines ( Fig. 7A, B ), surface often eroded and pitted even in live-collected shells; axial pleats on lower half of last whorl and around umbilicus ( Fig. 7D ), extending to adapical suture just prior to outer lip ( Fig. 7B ). Aperture narrower towards base on right hand side (in aperture view); peristome thickened and reflected; aperture markedly constricted by teeth, dentition nine-fold ( Fig. 7C ): 1) a parietal lamella, with outer portion markedly oblique and then curving inward so that remainder runs into aperture, and with a notch in its lower margin; 2) a large triangular labral tooth, its upper margin sinuous and with a denticle near lip edge and another further into aperture; 3, 4 and 5) two deeply inset ridge-like basal teeth in close apposition plus one behind labral tooth, visible through translucent shell, 6) a low, broad rounded denticle at base of somewhat thickened columella lip, and in some specimens, an even less prominent one at top of columella lip; 7–9) a large inset tricuspid columella lamella, the upper and middle teeth large and rounded (particularly the middle one), the lower one smaller, often little more than a bump. Labral tooth corresponds with a deep pit behind outer lip ( Fig. 7B ). Umbilicus widely open, elongate-oval, approx. 0.2 mm in length ( Fig. 7D ). Shell almost transparent when fresh, orange-red coloration of dried tissue of animal visible internally.

Distribution ( Fig. 2 )

Known only from Vernon Crookes Nature Reserve, in southern KwaZulu-Natal; at approx. 400 m above sea level.

Habitat

Patches of KwaZulu-Natal Scarp forest ( Mucina et al. 2018b); in leaf-litter and under logs.

Remarks

The two closely adpressed, ridge-like basal teeth are unusual; in taxa with a basal tooth to the right of centre, it is usually low and transverse, not in-running. The tricuspid columella lamella of Gulella crookesi sp. nov. resembles that of G. fordycei sp. nov. and several species from the Eastern Cape coast, particularly G. bomvana and G. kenbrowni sp. nov. The latter two taxa are also smooth and glossy. The labral tooth of G. crookesi sp. nov. is relatively larger than that of G. fordycei sp. nov., obstructing the aperture to a larger degree and obscuring the details of the columella lamella. The labral tooth of G. bomvana is also very large, but it extends behind the columella lamella.

Gulella crookesi sp. nov. also resembles the variable species, G. farquhari (Melvill & Ponsonby, 1895) , but the two basal teeth and tricuspid columella lamella immediately distinguish G. crookesi sp. nov.

Conservation

Gulella crookesi sp. nov. has been found only at Vernon Crookes Nature Reserve, a protected area under the jurisdiction of Ezemvelo-KZN Wildlife. The south coast of KwaZulu-Natal and hinterland have been extensively modified by sugarcane farming and development. Vernon Crookes Nature Reserve, although small, is a very important haven for biodiversity in the region. Twenty-nine species of terrestrial Mollusca have been recorded, including Chlamydephorus dimidius (Watson, 1915) , listed as Vulnerable and several other narrow-range species. It is the type and only known locality of two species of microchaetid earthworm, and the major locality for a third species which has also been recorded just outside the reserve ( Plisko 1998). The reserve is surrounded by sugarcane farms and rural villages, and portions of the fence are missing, enabling cattle to enter, which poses a threat to the integrity of the indigenous forest patches and the well-being of their litter-dwelling invertebrates.

Figures

Fig. 2. Distribution map of Gulella kenbrowni sp. nov. (pink circles), G. fordycei sp. nov. (blue squares), G. mkombeni sp. nov. (green triangles) and G. crookesi sp. nov. (orange square). Contour at 1000 m.

Fig. 7. Gulella crookesi sp. nov., holotype (NMSA P1680/T4526), length 2.44 mm, width 1.17 mm. A. Aperture view. B. Side view. C. View into aperture. D. Oblique view of base showing umbilicus. Scale bar = 0.5 mm.