Gulella benthodon van Bruggen, 1980

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 : 4-7

Gulella benthodon van Bruggen, 1980 stat. rev.

Figs 2–3

Gulella darglensis benthodon van Bruggen, 1980: 17–19 , fig. 6 (type locality: Pirie Forest near King Williams Town [R. Godfrey]).

Diagnosis

Shell very small, cylindrical; sculptured with strong axial ribs; apertural dentition eight-fold, including a strong in-running parietal lamella, a large mid-labral complex with a ridge-like upper margin running into aperture with a tooth near lip edge and another further into aperture, and a larger tooth on its lower margin further from lip edge, a low, inset transverse basal tooth to right of centre, an in-running ridge-like basal tooth to left of centre and a large inset bicuspid columella lamella with two ridge-like teeth; umbilicus widely open.

Type material (not examined)

Holotype SOUTH AFRICA – Eastern Cape • Pirie Forest, near King Williams Town [now Qonce]; ca 1920; R. Godfrey leg.; NHMUK 1937.12 .30.781.

Paratype SOUTH AFRICA • 1 spec.; same collection data as for holotype; NHMUK 1937.12 .30.782 .

Material examined

SOUTH AFRICA – Eastern Cape • 5 specs; Hogsback, Auckland Nature Reserve, downstream of Madonna and Child waterfall; 32.60701° S, 26.9625° E; 1043 m a.s.l.; 25 Jan. 2002; D. Herbert, M. Bursey and G. Redman leg.; NMSA W25 • 2 specs; Hogsback, Auckland Nature Reserve, Tyume River valley , downstream of Madonna and Child waterfall; 32.6055° S, 26.9603° E; 1030 m a.s.l.; 31 Dec. 2008; M. and K. Cole leg.; NMSA W6660 • 2 specs; same collection data as for preceding; ELMD 16135, ELMW 3343 • 1 spec.; same collection data as for preceding; NHMUK 20230166 , ex ELMD 16135 • 1 spec.; same collection data as for preceding; NMW.Z.2023.001.00001, ex ELMD 16135 • 1 spec.; same collection data as for preceding; RMNH.MOL.346278, ex ELMD 16135 • 2 specs; Hogsback, environs of Madonna and Child Waterfall, stn 14-02; 32.6070° S, 26.9625° E; 1043 m a.s.l; 6 Apr. 2014; D. Herbert, L. Davis and M. Cole leg.; NMSA W9731 • 1 spec.; Hogsback, Auckland Nature Reserve, Tyume River valley , downstream of Madonna and Child waterfall, south-facing slope; 32.6055° S, 26.9603° E; 1030 m a.s.l.; 4 Jan. 2022; M. Cole leg.; ELMD 19100 • 2 specs; Hogsback, Zinguka area, at base of large boulder near Wolfridge Road; 32.6495° S, 27.0025° E; 1086 m a.s.l.; 4 Jan. 2022; M. Cole leg.; ELMD 18881 .

Description

SHELL ( Fig. 2 ). Shell very small, cylindrical, length 3.0– 3.6 mm, width 1.3–1.5 mm, L:W 2.18–2.49 (n = 10). Protoconch approx. 0.9 mm in diameter, comprising approx. 2.5 whorls, smooth; junction between protoconch and teleoconch distinct. Teleoconch comprising nearly four whorls; first two whorls moderately convex, subsequent two more weakly so; whorls with faint subsutural angle delimiting narrow subsutural ramp; sculptured by well-developed axial ribs, extending from suture to suture (approx. 30 on penultimate whorl); rib intervals lacking sculpture ( Fig. 2A–B ). Aperture sub-quadrate with rounded base and shallowly indented outer lip; dentition eight-fold ( Fig. 2C ): 1) an oblique, in-running parietal lamella; 2–4) a large mid-labral complex itself with three teeth, its upper margin ridge-like and running into aperture with a tooth near lip edge and another further into aperture, and a larger rounded tooth on its lower margin set back from lip edge; 5) a low, inset transverse basal tooth to right of centre; 6) an in-running ridge-like basal tooth just to left of centre; 7–8) a large inset columella lamella set with two strong ridge-like teeth (there may also be a smaller bump below these, but it is not always obvious). Labral and basal teeth correspond with deep pits behind outer lip. Umbilicus widely open, elongate-oval, with a deep indentation underlying columella lamella ( Fig. 2D ). Shell almost transparent when fresh, orange-red coloration of dried tissue of animal visible internally.

Distribution ( Fig. 3 )

Endemic to the Amathole Mountains ; at altitudes between 1000 m and 1100 m above sea level.

Habitat

Amathole Mistbelt Forest (Southern Mistbelt Forest group) ( von Maltitz et al. 2003); in leaf-litter and under logs.

Remarks

We treat Gulella benthodon as a separate species and not as a subspecies of G. darglensis (Melvill & Ponsonby, 1908) as originally proposed. It bears very little resemblance to the other two subspecies of G. darglensis recognised by van Bruggen (1980). It has a large mid-labral complex with three cusps and not a pair of in-running ridge-like labral teeth. The columella lamella also has two strong ridge-like teeth, but both are inset, while in G. darglensis the lower tooth extends almost to the lip edge. The deeply situated columellar teeth were also noted by van Bruggen (1980) and were the origin of the subspecific name. Gulella benthodon has stronger and coarser sculpture than both subspecies of G. darglensis ; G. d. darglensis (Melvill & Ponsonby, 1908) has close-set axial riblets and G. d. illovoensis (Burnup, 1914) is smooth.

The apertural dentition of Gulella benthodon closely resembles that of G. kenbrowni Cole & Herbert, 2022 and G. fordycei Cole & Herbert, 2022 , but G. benthodon stands out at a glance by being strongly ribbed and considerably larger. The multi-toothed columella lamella is also reminiscent of G. aprosdoketa Connolly, 1939 , G. bomvana Cole & Herbert, 2009 and G. tietzae Cole & Herbert, 2009 , but these three species are smooth. The labral complex resembles that of several very small, narrow-range species endemic to Zululand, Gulella genialis (Melvill & Ponsonby, 1903) , Gulella laevorsa Burnup, 1925 and Gulella vallaris (Melvill & Ponsonby, 1907) in Group 9 of Herbert & Kilburn (2004), but none of the latter species have a multi-toothed columella lamella.

Conservation

Gulella benthodon is a narrow-range endemic found only in the Amathole Mountains where, despite fairly extensive collecting efforts throughout the mountain range, it has only been found at three localities. Van Bruggen’s (1980) specimens came from the Pirie Forest near King Williams Town, collected in about 1920. Recently collected specimens are known only from Hogsback and the majority were collected in the Auckland Nature Reserve. In spite of these being protected sites, poaching and illegal harvesting of plant products takes place and there is uncontrolled access of cattle.

Figures

Fig. 2.Gulella benthodon van Bruggen, 1980 status revised (NMSA W25), length 3.4 mm, width 1.4 mm. A. Aperture view. B. Side view. C. Detail of aperture. D. Oblique view of base showing umbilicus.

Fig. 3. Distribution map of Gulella benthodon van Bruggen, 1980 (blue triangles), G. judithmastersae sp. nov. (green squares), G. kevincolei sp. nov. (yellow circle) and G. mcmasteri sp. nov. (red diamonds) in the Amathole region of the Eastern Cape province. Contours at 1000 m and 2000 m.