Pseudavakubia atewaensis 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 : 651-654

Pseudavakubia atewaensis de Winter , sp. n.

Figs 28A–I, 29

Etymology: Name refers to the type locality, the Atewa Range Forest Reserve, one of very few mid-altitude forest areas in Ghana, which is severely threatened by illegal logging and plans for bauxite exploitation ( McCullough et al. 2007). The area has a very high land snail diversity, with various land snail taxa not found elsewhere in Ghana so far (de Winter, Tattersfield & Nutsuakor, unpubl. data).

Diagnosis: P. atewaensis differs from P. ghanaensis by having less depressed apical whorls, a straight palatal lip (not arching forward in lateral view), a more rounded peristome, and a more angulate and proportionally smaller body whorl. The holotype shell of P. liberiana is smaller and less slender with a proportionally larger body whorl and a weaker palatal tooth. P. majus has a distinctly larger and more cylindrical shell with less tightly coiled whorls.

Description:

Shell ( Figs 28A–H, 29): Small (H 3.3–3.4 mm), subcylindrical to strongly biconical, high-spired (H:D 1.75–1.85), greatest diameter at penultimate whorl. Whorls above widest portion of shell moderately to strongly tapering towards apex. Whorls 6¾, moderately convex, whorl increase comparatively slow (coiling tightness ca 5.7). Protoconch diameter 1.0– 1.1 mm. Protoconch irregularly coiled, which is noticeable in lateral views of the shell. First 1¼ whorls distinctly raised above nucleus, providing apex with strongly distorted­acuminate appearance, with very fine spiral sculpture crossed by low growth lines ( Fig. 29B), appearing smooth and shining at lower magnification. Later protoconch (ca ¾ whorl) with six distant spiral ridges. Transition of ‘smooth’ to spirally sculptured portion of protoconch abrupt, transition from protoconch to teleoconch more gradual, first 5 axial ribs of the teleoconch being crossed by spiral cords. Body whorl proportionally small, BWH 38–39 % of H. Periphery of body whorl somewhat angular. Peristome entire, incrassate, proportionally small, roundish in outline, about as high as wide or wider than high, PH:PW 0.93–1.03, PH 29% of H, PW 0.5–0.56 % of D. Palatal margin of peristome in lateral view comparatively straight, not arching forward.Angular tooth somewhat protruding, continuing as deeply entering lamella. Tooth on mid-palatal wall strong and pointed. Umbilicus closed, umbilical chink with radiating ribs. Teleoconch sculpture consists of slightly oblique, curved axial ribs, 8.7–8.8 ribs/mm, with fine spirals in interstices.

Body colour: Dried-in soft parts of holotype reddish.

Anatomy: Unknown.

Holotype: GHANA: Eastern Region : Atewa Range Forest Reserve, 6.24558°N 0.54654°W, 660 m, 22.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter, steep E­facing slope in upland evergreen forest ( RMNH. MOL.123111).

Paratype: 1 ad. shell in alcohol, same data as holotype ( NMW.Z.2013.055.00002) .

Other material examined: GHANA: Eastern Region : 1 juv. dry shell Atewa Range Forest Reserve, 6.12368°N 0.60445°W, 655 m, 23.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter, SE­facing slope in recently logged upland evergreen forest ( RMNH.MOL.330214) .

Distribution ( Fig. 31): Only known from the Atewa Range Forest Reserve in Ghana.

Habitat: Both adult specimens were obtained from floor litter samples in upland evergreen forest at about 650 m. A juvenile was collected from the understorey vegetation. Found sympatrically with P. majus .

Remarks: P. atewaensis resembles P. liberiana , sharing a strait palatal lip, a proportionally small, rounded peristome and close-set axial ribs on the teleoconch. The holotype shell of P. liberiana is smaller and less slender with a proportionally larger body whorl and a weaker palatal tooth.