Pseudavakubia liberiana de Winter, 2013

de Winter, A. J. & Vastenhout, N., 2013, Revision of the Afrotropical land snail genus Avakubia Pilsbry, 1919, with description of Pseudavakubia gen. n. and eleven new species (Gastropoda: Pulmonata: Streptaxidae), African Invertebrates 54 (2), pp. 605-663 : 657

Pseudavakubia liberiana de Winter , sp. n.

Figs 28J–N

Gulella (Avakubia) avakubiensis: Degner 1934 b: 377 .

Description:

Shell ( Figs 28J–N): Rather small (H 2.9 mm), ovoid-biconical, H:D 1.68, greatest diameter at penultimate whorl. Whorls above widest portion of shell moderately tapering towards apex. Whorls 6, strongly convex, whorl increase slow (coiling tightness 5.6). Protoconch diameter 1.15 mm. Protoconch irregularly coiled, which is noticeable in lateral views of the shell. First ca 1¼ whorls distinctly raised above nucleus, giving apex a distorted, acuminate appearance, with extremely fine spiral sculpture, appearing smooth and shining at lower magnification. Transition to spirally sculptured portion of the protoconch marked by axial thickening and slight change in colour. Spirals on later protoconch portion (ca ¾ whorl) initially extremely weak and confined to lower quarter of whorl. Sculpture becomes more prominent (but still comparatively weak), towards teleoconch, where six or seven fine spiral cords discernable. Body whorl 44% of H. Periphery of last whorl slightly angular. Peristome entire, incrassate, roundish in outline, wider than high, PH:PW 0.89, PH 30% of SH, PW 57 % of D. Palatal-basal lip in lateral view comparatively straight, not arching forward. Angularis is a somewhat protruding tooth, continuing inwards as low lamella for at least half a whorl. Tooth on mid-palatal wall rather weak. Umbilicus fully closed, umbilical depression with radiating ribs. Teleoconch sculpture consists of slightly oblique, axial ribs, about 9.1 ribs/mm, with fine spirals in interstices.

Body colour: Unknown.

Anatomy: Unknown.

Holotype: LIBERIA: Banga , ca 7.28°N 10.06°W, ca 200 m, 1926–1927, J. Bequaert, Harvard African Expedition ( MCZ 77342 ).

Distribution ( Fig. 31): Only known from the type locality.

Remarks: This species is represented by a single fresh shell only, which was originally identified as a specimen of A. avakubiensis (Degner 1934 b) . It best resembles P. atewaensis , of which it eventually may turn out to be a geographical form. However, the Liberian shell was collected at some considerable distance (almost 1000 km) from the Atewa Range, and differs by a smaller shell with more convex whorls, larger protoconch with more and finer spiral cords, a proportionally larger body whorl, and a much weaker tooth on the palatal lip. We prefer to describe this shell as specifically distinct. More material is required to test this taxonomic decision.

The holotype shell exhibits a pale marking on the body whorl which might be incorrectly interpreted as the palatal fold characteristic of the genus Avakubia . By means of a CT­scan the absence of internal barriers could be confirmed.