Gulella hamerae, Bursey & Herbert, 2004

Bursey, M. L. & Herbert, D. G., 2004, Four new narrow-range endemic species of Gulella from Eastern Cape, South Africa (Mollusca: Pulmonata: Streptaxidae), African Invertebrates 45, pp. 249-262 : 250-252

Gulella hamerae sp. n.

Figs 1–5 , 24

Etymology: Named for Dr Michelle Hamer, University of KwaZulu-Natal, who has devoted much time and effort to the study and conservation of southern African invertebrates.

Diagnosis: Shell minute, oval-cylindrical; sculptured with strong axial ribs; peristome entire, but fused to base of preceding whorl in parietal region; aperture y-shaped, columella strongly indented; dentition five-fold: a parietal lamella, two labral denticles, a basal denticle and a large curved superficial tooth on indented columella; embryonic shell sculptured with close-set, spiral lirae; umbilicus open, relatively wide (width 1.4– 1.6 mm) and deep.

Description: Shell minute, oval-cylindrical, length 2.7–3.1 mm, width 1.5–1.65 mm; length:width 1.70–1.96. Embryonic shell approx. 0.88 mm in diameter, comprising approx. 2.25 whorls; sculptured more or less throughout with close-set, microscopic raised spiral threads ( Fig. 5 ), last half whorl also with fine, close-set axial riblets radiating from suture; junction between embryonic shell and teleoconch distinct. Teleoconch comprising approx. 4.5 whorls; first whorl convex, but subsequent ones rather more flat-sided; suture narrowly indented; sculpture of strong, sigmoid axial ribs, extending from suture to suture (47–49 on penultimate whorl); prosocline on spire whorls and almost orthocline on last whorl; rib intervals lacking obvious microsculpture ( Fig. 4 ) and with only occasional traces of spiral threads on sides of ribs. Peristome entire and fused with base of penultimate whorl in parietal region, flaring outward elsewhere. Aperture constricted, y-shaped with lower limb curving toward shell axis, columella strongly indented; apertural dentition five-fold ( Fig. 3 ): 1) a strong parietal lamella, outer portion oblique and then curving inward so that remainder runs into the aperture more or less at right angles, a distinct ridge-like swelling at point of curvature; 2-3) two broad labral teeth, upper one flat-topped and level with apertural margin, lower one flat-topped or somewhat rounded and inset well behind upper one; 4) a deep-set, small, transverse basal tooth; 5) a large curved columella tooth level with aperture margin, but angled inward basally; a lamella on inner part of columella is not evident. Labral complex corresponds with an external pit behind flaring outer lip. Umbilicus relatively wide (width 1.4–1.6 mm) and deep, with a conspicuous pit underlying columella tooth. Shell translucent, uniformly milky-white when fresh.

Type material: Holotype: NMSA W1217 /T1999, length 2.7 mm, width 1.52 mm. South Africa, Eastern Cape, Transkei, Nqadu Forest, north of Umtata , leg. H.J. Puzey (undated).

Paratype 1, NMSA V9127 /T1998, Eastern Cape, Transkei, Nqadu Forest (31º25.665'S: 28º45.118'E), north of Umtata , leg. D. Herbert, 12/v/2001 .

Paratypes 2, 3, NMSA W223 /T2009, paratype 4, NMW Z.2004.030.00001 and paratype 5, ELM 13661 , Eastern Cape, Transkei, Nqadu Forest, north of Umtata , leg. W.G. Rump, 1935 .

Paratypes 6,7, RMNH 98152 , Eastern Cape, Transkei, Nqadu Forest, north of Umtata , leg. W.G. Rump, 1935, ex coll’n W. Falcon, don. H. Boswell via A.C. van Bruggen .

Distribution and habitat ( Fig. 24 ): Known only from Nqadu Forest, north of Umtata, Eastern Cape; Transkei mist-belt forest, in leaf-litter.

Remarks: G. hamerae is evidently related to G. claustralis Connolly, 1939 , a species known only from two mist-belt forest localities in northern Pondoland and southern KwaZulu-Natal ( Herbert & Kilburn 2004). The strong axial sculpture, y-shaped aperture, entire peristome, indented columella lip, and spirally striate embryonic shell are evidence of this. It differs, however, in the form of the labral teeth (lower cusp absent) and in its much more strongly indented columella, the inner margin of which possesses a single strong, smoothly curved tooth, instead of two distinct teeth. In terms of its columella morphology, G. hamerae somewhat resembles G. incurvidens Bruggen, 1972 , from the northern Drakensberg and Soutpansberg (Mpumalanga and Limpopo provinces), but that species evidently lacks spiral sculpture on the embryonic shell, has a single in-running labral tooth and the basal part of its aperture is twisted obliquely upward. It seems probable that G. hamerae and G. claustralis are sister taxa, having evolved from fragmented populations of a single, more widespread progenitor.

Figures

Figs 1–5. Gulella hamerae sp. n., holotype. 1, 2, apertural and lateral views of shell, length = 2.7 mm; 3, oblique view into aperture, bar = 0.25 mm; 4, detail of sculpture (start of last whorl), bar = 100 µm; 5, microsculpture on embryonic shell, bar = 100 µm.

Fig. 24. Map of northern Eastern Cape showing distribution of new species.