Avakubia ortizdezarateorum de Winter & Vastenhout, 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 : 637-640

Avakubia ortizdezarateorum de Winter & Vastenhout , sp. n.

Figs 19, 21A, B

Gulella (Avakubia) avakubiensis: Ortiz de Zárate Lopez & Ortiz de Zárate Rocandio 1956: 118 (in part).

Etymology: The species is named after Adolfo Ortiz de Zárate Lopez and his son Antonio Ortiz de Zárate Rocandio, who collected and described this peculiar form without formally naming it.

Diagnosis: Shell easily distinguished by the very fine, close­set axial ribs, and narrow apertural lip. In contrast to all other congenerics, the palatal fold and columellar lamella whorl can be seen in the aperture in oblique view. Spiral sculpture on protoconch little conspicuous.

Description:

Shell ( Figs 19, 21A, B, Table 1; all shells except holotype are in poor condition): Small (mean H 3 mm), fragile, ovate-biconical, largest width at penultimate whorl. H:D 1.69–1.78, median 1.75, in holotype 1.69. Coiling tightness 4.4–4.6, median 4.6, in holotype 4.6. Whorls little convex. Protoconch raised, but not acuminate, consisting of ca 2.0 whorls. Protoconch sculpture consists of low and little conspicuous spiral cords, ca 15–20 on second whorl, each <10 µm wide. Distinction between major cords and thinner, irregularly spaced lines is gradual. Cords composed of low, barely separated, elongate-oval or rectangular-squarish particles (ca 6–12 µm long). Teleoconch whorls somewhat smooth with patches of very fine, more or less regular, close­set ribs, about 20 ribs/mm on penultimate whorl, giving the shell a silky lustre. Spiral sculpture on teleoconch present but little prominent; very fine spiral lines in interstices appear continuous where ribs are low. Body whorl proportionally small, BWH 44–47 % of H, median 46%, in holotype 47%. Peristome complete, slightly higher than wide; PH:PW 1.06–1.15, median 1.09, in holotype 1.1. PH 29–33% of H, median 32%, in holotype 33%. PW 44–54% of D, median 52 %, in holotypee 50 %. Apertural lip little expanded, thin, hardly reflected. Slightly projecting angular tooth extends inwards as high, deeply entering lamella. Mid-palatal wall slightly indented, palatal tooth or labial thickening is virtually wanting. Wall of body whorl with deep-set, short palatal fold, together with columellar lamella discernable in aperture in oblique view ( Fig. 19F). Umbilicus extremely narrow, but open .

Body colour: Unknown.

Anatomy: Unknown.

Holotype: ECUATORIAL GUINEA: Bioko I.: Refugio del Pico Basilé (formerly Pico de Sta Isabel), ca 3.6116°N 8.7783°W, up till (“hasta”) 2350 m, 1.i.1946 ( MNCN 15.05 /26566).

Paratypes: ECUATORIAL GUINEA: Bioko I.: 5 damaged dry shells, Pico Basilé, 2000 m, Antonio Ortiz de Zárate ( MNCN 15 /05/26567) .

Distribution ( Fig. 8): Only known from the type locality and probably endemic to the Island of Bioko.

Habitat: This species has been found at around 2000 m, the highest known altitude for any Avakubia species.

Remarks: Ortiz de Zárate Lopez and Ortiz de Zárate Rocandio (1956) already recognised substantial differences in shell morphology between this high altitude form and the lowland type of “ Gulella (Avakubia) avakubiensis ” on Bioko I. (here treated as a separate species A. biokoensis , sp. n.), which they attributed to different climatic conditions. However, A. ortizdezarateorum is very distinct conchologically. It differs not only considerably in size, but also in the rather different arrangement of apertural barriers and in sculpture of both the protoconch and teleoconch, which characters also separate it from all other Avakubia species. These peculiarities may well be grounds to assign it to a different (sub)genus, but this should be based on more, preferably alcohol preserved, specimens.