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Revision of the Afrotropical land snail genus Avakubia Pilsbry, 1919, with description of Pseudavakubia gen. n. and eleven new species (Gastropoda: Pulmonata: Streptaxidae).

Avakubia occidentalis de Winter, sp. n.

Figs 16, 21C, D

Etymology: From Latin occidentalis (western), in reference to the westernmost distribution of this species among any known Avakubia species.

Diagnosis: A small species of Avakubia, differing from similar-sized congenerics by a combination of conchometrical characters, as well as by the large number of spiral cords on the protoconch.

Description:

Shell (Figs 16, 21C, D, Table 1): Small to medium-sized (mean H 3.3 mm), subcylindrical, largest width at penultimate whorl. H:D 1.59-1.84, in holotype 1.84. Number of whorls 5-5.5. Coiling tightness 4.45-4.65, in holotype 4.45. Whorls moderately convex. Protoconch slightly acuminate, consisting of ca 2 whorls. Protoconch on second whorl with >16, more or less regularly spaced cords, 6.3-8.6 pm wide, without finer spiral lines between them. Spiral cords made up of series of adjoining, poorly differentiated rectangular particles of variable length (ca 8-19 [micro]m). Teleoconch sculpture of regularly spaced, curved axial ribs, 9.0-10.0 ribs/mm on penultimate whorl, median 9.9 ribs/mm, in holotype 9.0, with fine spirals in interstices. BWH 48-49% of H, in holotype 48%. Peristome holotype entire (peristome of other shells damaged, PW measurements not accurate). PH:PW 0.88-1.10, in holotype 1.06. PH 32-34% of H, median 34%, in holotype 34%. PW 52-59% of D, median 56%, in holotype 59%. Apertural lip expanded and flaring, reflected and incrassate in holotype. Two barriers visible in aperture: a blunt, tooth-like thickening on mid-palatal wall and a conspicuous angular tooth that extends inwards as deeply entering lamella. Internal wall of body whorl with deeply-set palatal fold, externally barely visible in opaque shells. Columellar lamella not visible in aperture, but probably present. Umbilicus punctiform but open, slightly wider than in A. fruticicola.

Body colour: Soft parts at least partly reddish (dried-in tissue paratype).

Anatomy: Unknown.

Holotype: GHANA: Volta Region: Logba Tota, 6.88363[degrees]N 0.46804[degrees]E, 470 m, 30.i.2010, P. Tattersfield, M.E. Nutsuakor & A.J. de Winter, semi-deciduous forest on steep slope near waterfall (NMW.Z. 2013.055.00001).

Paratype: 1 dry shell, same data as holotype (RMNH.Mol.254654).

Other material examined: GHANA: Eastern Region: 1 dry shell, Atewa Range Forest Reserve, 6.12368[degrees]N 0.60445[degrees]W, 655 m, 23.i.2010, P. Tattersfield, M.E. Nutsuakor & A.J. de Winter, in litter of recently logged high forest (RMNH.MOL.330190).

Distribution (Fig. 17): Known from two localities in eastern Ghana.

Habitat: Found in semi-deciduous forest near waterfall at 470 m, as well as in upland evergreen forest at 650 m. All specimens were collected from the forest floor.

Remarks: This species superficially resembles A. fruticicola in size, teleoconch sculpture and colour of the soft parts. However, the Ghanaian shells differ in a number of characters, such as a more cylindrical shell, tighter coiled whorls (about half a whorl more at the same size), proportionally smaller body whorl, more pointed apex, and slightly wider umbilicus and wider spaced axial ribs, in addition to details of the protoconch sculpture. Two A. occidentalis specimens were found alive on the forest floor, whilst specimens of A. fruticicola were exclusively collected from the understorey vegetation. The Ghanaian localities are situated some 1200 km from those of A. fruticicola in Cameroon.

Avakubia occidentalis is the only Avakubia species known in the Upper Guinea forest block. Traditionally postulated biogeographic barriers like the Dahomey Gap and Cross River have apparently not restricted the distribution of the genus, which might suggest a considerable age for the taxon. On molecular grounds Rowson et al. (2011) suggested Avakubia to be an ancient taxon that possibly survived the Mesozoic/Cainozoic mass extinctions, whilst the streptaxid diversity is otherwise known from the Cainozoic only.

Avakubia ortizdezarateorum de Winter & Vastenhout, sp. n.

Figs 19, 21A, B

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

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

Diagnosis: Shell easily distinguished by the very fine, close-set 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 pm 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 pm long). Teleoconch whorls somewhat smooth with patches of very fine, more or less regular, close-set 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 Basile (formerly Pico de Sta Isabel), ca 3.6116[degrees]N 8.7783[degrees]W, up till ("hasta") 2350 m, 1.i.1946 (MNCN 15.05/26566).

Paratypes: ECUATORIAL GUINEA: Bioko I.: 5 damaged dry shells, Pico Basile, 2000 m, Antonio Ortiz de Zarate (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 Zarate Lopez and Ortiz de Zarate 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.

Avakubia semenguei de Winter & Vastenhout, sp. n.

Figs 20, 21E-G

Gulella (Avakubia) n. sp.: de Winter & Gittenberger 1998: 240.

Etymology: The species is named after Eric-Joel Semengue, in recognition of the importance of his guiding and collection assistance in the field.

Diagnosis: A. semenguei is easily recognised from other Avakubia species by its large ovate shell (only the shell of A. acuminata is larger) with rapidly increasing whorls, flattened apex and very wide protoconch.

Description:

Shell (Figs 20, 21E-G, Table 1): Large (mean H 4.9 mm), largest width at penultimate whorl. H:D 1.66-1.77, median 1.70, in holotype 1.66. Whorls expanding rapidly, coiling tightness 3.1-3.3, median 3.2, in holotype 3.2. Whorls moderately convex. Protoconch little elevated, consisting of ca 2.0-2.25 whorls. Apex comparatively flat. Protoconch sculpture consists of ca 11 distinct, comparatively conspicuous spiral cords, each 9-14 gm wide, consisting of poorly individualized, irregular-rectangular or quadrangular particles, on average 9 particles per 100 gm. In many spots the coarse spirals resemble wrinkled continuous cords, rather than series of beads. One or two spirals of intermediate coarseness, as well as very thin lines, occur occasionally between major cords. Teleoconch sculpture consists of obliquely curved axial ribs, with rather irregularly spaced spiral lines in interstices, 8.7-11.5 ribs/mm on penultimate whorl, median 10.5 ribs/mm, in holotype 11.5 ribs/mm. Last whorl proportionally large, BWH 51-54% of H, median 53%, in holotype 53%. Peristome complete, higher than wide; PH:PW 1.08-1.29, median 1.16, in holotype 1.15. Peristome proportionally large: PH 36-40% of

shell height, median 39%, in holotype 40%. PW 54-59% of shell width, median 57%, in holotype 58%. Apertural lip expanded and flaring, slightly reflected, not strongly incrassate. Two barriers visible in aperture: a weak (or almost wanting) thickening on mid-palatal wall and not (or barely) projecting angular tooth that extends inwards as deeply entering lamella. Internal wall body whorl with comparatively long, deep-set palatal fold, externally visible in fresh specimens as a pale stripe (Figs 20C, E). Columellar lamella not visible in aperture. Umbilicus rather narrow but open.

Body colour: Soft parts of live animal pale, without reddish pigment.

Anatomy: Unknown.

Holotype: CAMEROON: Sud Prov.: Minwo area, 6 km NE of Ebom, 15 km S of Lolodorf, plot I2 (de Winter & Gittenberger 1998), sta. CAM.055a, 3.10[degrees]N 10.73[degrees]E, 520 m, 21.iii.1996, A.J. de Winter & E.-J. Semengue, undisturbed high forest on hilly terrain (RMNH.MOL.330191).

Paratypes: CAMEROON: all from same square km as holotype, same collectors: 2 ad., 1 juv. dry shell, sta. CAM.022a, 470 m, 21.ix.1995 (RMNH.MOL.42809); 1 ad. dry shell, sta. CAM.028a, 400 m, 27.ix.1995 (RMNH.MOL.330192); 1 ad. dry shell, sta. CAM.039a, 470 m, 6.x.1995 (RMNH.MOL.42810); 1 juv. dry shell, sta. CAM.065, 470 m, 2.iv.1996 (RMNH.MOL.330193); 1 juv. in alcohol, sta. CAM.070a, 590 m, 2.iv.1996 (RMNH.MOL.330194); 1 juv. dry shell, sta. CAM.076a, 480 m, 9.iv.1996 (RMNH.MOL.330195); 4 juv. in alcohol, sta. CAM.082a, 470 m, 12.iv.1996 (RMNH.MOL.330196).

Distribution (Fig. 25): Only known from a single square km in Southwest Cameroon, 90 km east of Kribi. The collecting technique of beating the vegetation over an umbrella was used extensively in other areas in Southwest Cameroon, but yielded only other Avakubia species. The species might be a narrow range endemic.

Habitat: Collected from understorey vegetation up to 3 m above the forest floor in relatively undisturbed rainforest between 400 and 500 m. The species lives syntopically with A. acuminata and A. fruticicola, which are also arboreal.

Avakubia subacuminata de Winter & Vastenhout, sp. n.

Figs 5G, 22-24

Etymology: Refers to the superficial resemblance to the larger and more strongly acuminate A. acuminata.

Diagnosis: Superficially resembles A. acuminata by the acuminate apex and tapering spire, but has a much smaller, shorter-spired shell with tighter coiled whorls and a less sharp apical angle. The shell of A. avakubiensis is generally smaller with less tightly coiled whorls, proportionally larger body whorl, more convex protoconch whorls, and less acute apex. It is easily distinguished from other Avakubia species by the acuminate apex, proportionally small body whorl and slowly increasing whorls, among other characters.

Description:

Shell (Figs 22, 23, Table 1): Small to medium-sized (mean H 3.8 mm), ovate-biconical, largest width at penultimate whorl, occasionally preceding whorl equally wide. H:D 1.65-1.93, median 1.75, in holotype 1.76. Whorls expanding rather slowly, coiling tightness 4.5-5.0, median 4.8, in holotype 4.8. Whorls moderately convex. Apex acuminate. Protoconch with ca 2.0-2 1/4 whorls. Protoconch of specimens from the Ebimimbang area with 10-11 major spiral cords on second whorl, each at most 6.5 pm wide, usually somewhat less, made up of rectangular particles of rather unequal size (each ca 5-17 [micro]m long, on average 9 particles per 100 pm), which become individually less distinct towards teleoconch. Major cords irregularly interspaced by thinner, seemingly solid, lines. Material from the Nyangong area has a larger number of somewhat wider (up to 8 [micro]) major cords (12-15) on second whorl; distinction between major and minor cords much less clear than in the Ebimimbang material, and individual particles appear to be shorter, but they are individually less clearly recognisable than in the Ebimimbang material. Teleoconch with sculpture of slightly oblique, regularly spaced axial ribs, ca 6.6-9.4 ribs/mm on penultimate whorl, median 7.6 ribs/mm, in holotype 6.9 ribs/mm, interstices with fine, comparatively regularly spaced spiral lines. Last whorl proportionally small, BWH 38-45% H, median 41%, in holotype 42%. Peristome entire, proportionally small, generally slightly higher than wide; PH:PW 0.97-1.15, median 1.07, in holotype 1.09. PH 29-32% of H, median 31%, in holotype 32%. PW 48-56% of D, median 51%, in holotype 51%. Apertural lip expanded and flaring, slightly reflected, not strongly incrassate. Two barriers visible in aperture: a weak or almost wanting, tooth-like thickening on mid-palatal wall and a projecting angular tooth that extends inwards as deeply entering lamella. Wall of body whorl with deep-set palatal fold (Fig. 5G), externally visible in fresh specimens as a pale stripe (Figs 22C, E). Columellar lamella rather small (Fig. 5G), not visible externally. Umbilicus narrow, slightly more open than in most other Avakubia species.

Body colour. Live animal with orange-reddish soft parts.

Anatomy (Fig. 24; one specimen dissected): Atrium about as wide as long, thin-walled. Penis subcylindrical, elongate, with short apical caecum as well as lateral diverticulum that is longer than wide. Vas deferens convolute along female genital tract, becoming more straight, wider and muscular upon reaching penis; it enters penis subapically cutting off a short caecum. Penis retractor muscle convolute, originating from columella muscle and inserting on penial apex, extending under terminal portion of vas deferens. Interior of distal penis without obvious pilasters but with irregularly-shaped tissue pads. Vagina short but distinct. Bursa copulatrix with ca 2.5 mm long narrow duct and elongate terminal sac close to albumen gland. Free oviduct short. Hermaphrodite duct with long, tube-like, convolute talon. No chitinous spines found inside penis.

Radula: No complete row could be studied, but individual lateral/marginal teeth are similar in shape to those in A. acuminata.

Holotype: CAMEROON: SudProv.: Ebimimbang, ca 3 km SW of Saa, sta. CAM.124, 3.033[degrees]N 10.443[degrees]E, 150 m, 28.v.1996, A.J. de Winter & E.J. Semengue, high forest on slope (RMNH.MOL.330197).

Paratypes: CAMEROON: SudProv.: all within 5 km from Ebimimbang-Saa, S of the Bikoui River (= R. Lokoundje), same collectors as holotype: 1 ad. dry shell Ebimimbang, ca 2 km WSW of Saa, sta. CAM.042, 3.038[degrees]N 10.456[degrees]E, 120 m, 10.x.1995, swamp forest (RMNH.MOL.330198); 1 ad. dry shell, Ebimimbang, 1 km SW of Saa, sta. CAM.043, 3.041[degrees]N 10.457[degrees]E, 110 m, 11.X.1995, high forest on flat terrain (RMNH. MOL.330199); 2 ad. dry shells, 1 ad. in alcohol Ebimimbang, sta. CAM.051, 3.038[degrees]N 10.477[degrees]E, 120 m, 12-18.X.1995, 25-year-old cocoa plantation with scattered large forest trees (RMNH.MOL.330200-330201); 1 ad., dissected soft parts in alcohol, Ebimimbang, 1 km S of Saa, secondary forest on an abandoned field along River Bikoui (= R. Lokoundje), sta. CAM.052, 3.042[degrees]N 10.467[degrees]E, 110 m, 19.X.1995, floor litter (RMNH.MOL.330202); 1 ad. dry shell, sta. CAM.052, 23.v.1996 (RMNH.MOL.330203); 1 juv. dry shell, Ebimimbang, 4 km WSW of Saa, high forest, sta. CAM.117, 3.050[degrees]N 10.433[degrees]E, 150 m, 25.V.1996 (RMNH.MOL.330204); 2 ad. dry shells, Ebimimbang, 4 km W of Saa, swamp forest, sta. CAM.120, 3.050[degrees]N 10.433[degrees]E, 120 m, 27.V.1996 (RMNH.MOL.330205); 1 ad. in alcohol, Ebimimbang, 4 km W of Saa, swamp forest, sta. CAM.129, 3.050[degrees]N 10.433[degrees]E, 120 m, 29.V.1996 (RMNH.MOL.330206); 1 ad. dry shell Ebimimbang, 3 km WSW of Saa, young secondary forest, sta. CaM.133, 3.046[degrees]N 10.435[degrees]E, 110 m, 30.V.1996 (RMNH.MOL.330207).

Other material examined: CAMEROON: Sud Prov.: 1 juv. dry shell, Nyangong, 30 km S of Lolodorf, undisturbed rainforest, sta. CAM.100, 2.943[degrees]N 10.736[degrees]E, 700 m, 7.v.1996 (RMNH.MOL.330208); 1 ad., 4 juv. dry shells, Meka'a II, W of Nyangong, undisturbed rainforest, sta. cAm.106, 107, 110, 111, 2.967[degrees]N 10.733[degrees]E, 690-1000 m, 17-18.v.1996 (RMNH.MOL.330209-330212).

Distribution (Fig. 25): Known from two areas in Southwest Cameroon, which are some 35 km apart and differ substantially in altitude (100-150 m in Ebimimbang vs 6901000 m in Nyangong).

Habitat: Collected from leaf-litter on the forest floor, except for a single specimen in a vegetation beating sample. The species was taken at ca 100-150 m in a variety of habitats: little disturbed high forest, more or less undisturbed swamp forest, a 25-year-old cocoa plantation with some remaining forest trees as well as in young secondary forest. A few specimens were collected in floor litter in undisturbed forest at 690-1000 m altitude (see below). In the Ebimimbang area A. subacuminata appears to be the only Avakubia species present (but see Remarks); in the Nyangong area it occurs sympatrically with A. fruticicola, which inhabits the understorey vegetation, however.

Remarks: A. subacuminata superficially resembles A. acuminata in shape, but is not a small geographic form of this species. Apart from clear conchological differences, the animal is differently coloured (reddish orange instead of colourless/whitish), the genital anatomy differs in various details, and the species has ground-dwelling rather than arboreal habits. A. subacuminata does not seem to occur in an intensively sampled square km of forest in between both localities at an intermediate altitude (400-500 m), where three other Avakubia species were observed. The attribution of the Nyangong material to A. subacuminata is somewhat doubtful, because of small differences in protoconch sculpture details. The only adult shell from the Nyangong area could not be separated from the lowland specimens by shell proportions, however. Confirmation of the tentative identification requires collection of fresh material for anatomical and molecular studies.

Two juvenile shells with Avakubia-like sculpture were collected in leaf-litter in the Ebimimbang area. The protoconchs are very small and possess a more acuminate apex than any of the recognised Avakubia species, as well as distinctive coarse spiral sculpture (Figs 23E, F). These potentially represent still another unknown Avakubia species, but adult shells are necessary to confirm the tentative generic attribution.

Genus Pseudavakubia de Winter & Vastenhout, gen. n.

Etymology: The name refers to the strong resemblance of the shells to those of the genus Avakubia. Gender feminine.

Type species: P majus de Winter & Vastenhout, sp. n.

Description: Shell small, H 2.9-4.3 mm, elongate ovate or cylindrical, penultimate whorl always wider than body whorl, with 6-7 1/4 whorls that generally expand slower than in Avakubia species, hence coiling tightness is higher (4.9-5.8). Last whorl proportionally smaller than in most Avakubia species, taking up 38-44% of H. Peristome proportionally small, PH 29-35% of H, PW 50-57% of D. Aperture in most species (P liberiana excepted) with a conspicuous, pointed palatal tooth, and a protruding angular tooth that continues as a deeply inrunning angular lamella. Palatal fold and columellar lamella absent. Umbilicus closed, umbilical depression with radiating ribs. Protoconch with ca 2 1/4 whorls not regularly increasing in width, but appearing more or less laterally compressed. Protoconch consists of two distinct portions: the first ca 1% whorls appear rather smooth and shining at lower magnification, but at high magnification fine spiral sculpture can be distinguished (Fig. 29B); the sculpture changes abruptly to sharp, distant spiral cords on the last ca 3/4 whorl. These spiral cords are solid, not composed of series of particles as in Avakubia (Fig. 29C). Teleoconch sculpture consists of sharp, regular ribs, with fine spiral lines in the interstices.

Anatomy (Fig. 27; based on a single dissection of P majus): Penis twice as long as wide, muscular, robust, with a strong retractor muscle inserting subapically, next to the entrance site of the vas deferens, cutting off a short, spherical apical caecum. Vas deferens proximally rather straight, becoming convolute between the vagina and penial apex; the terminal portion somewhat rounded, swollen and muscular, narrowing just before entering the penis. Penis internally with two bulky, longitudinal pilasters. No chitinous spines were found inside the penis. Vagina short but distinct, rather wide close to the penis. Free oviduct abruptly widening into a pouch-like uterus containing a single, shelled embryo. Duct of bursa copulatrix rather long, distally widest, tapering towards the small bursal sac, which is situated close to the albumen gland. Talon a long, stiff, exposed, tube at the base of the (remains of) the albumen gland. Spermoviduct with large, elongate acini. Radula typical carnivorous; a complete row no could be studied; individual lateral/marginal teeth elongate, curved and sharply pointed, similar in shape to those in A. acuminata.

Species included: In addition to the type species, P atewaensis de Winter, sp. n.; P. ghanaensis de Winter, sp. n.; P liberiana de Winter, sp. n.

Distribution: Ghana, Liberia.

Pseudavakubia majus de Winter & Vastenhout, sp. n.

Figs 26, 27

Etymology: From Latin majus (larger), in reference to the comparatively large shell of this species.

Diagnosis: A comparatively large, cylindrical species of Pseudavakubia.

Description:

Shell (Fig. 26): Large, H 4.3 (holotype)--4.4 mm, cylindrical-biconical, largest width at penultimate whorl, high-spired, H:D 1.94-1.95. Whorls 7 1/4, little convex, whorl increase fast, coiling tightness 4.9-5 (holotype). Protoconch diameter 1.4 (holotype)--1.6 mm. Protoconch irregularly coiled, whorl diameter increase of first whorls uneven. First 1 1/2 protoconch whorl almost smooth (not studied with SEM), shining. Remaining 3/4 protoconch whorl with 5-6 low, irregularly spaced cords. Boundary between smooth and spirally sculptured portion of protoconch sharp; transition from protoconch to teleoconch more gradual with a short zone of reticulate sculpture of axial ribs crossed by spirals. Body whorl proportionally large, BWH 42-44% of H, in holotype 42%. Periphery of last whorl rounded. Peristome entire, not strongly incrassate, higher than wide, PH:PW 1.06-1.14, in holotype 1.14. PH 33-34% of H, in holotype 33%, PW 57-62% of D, in holotype 57%. Palatal-basal lip in lateral view curved and arching forward. Tooth on mid-palatal wall blunt. Angular tooth protrudes, proceeding inwards as low, deeply entering lamella. Umbilicus closed, umbilical depression with radiating ribs. Teleoconch sculptured by slightly oblique, regularly spaced axial ribs, 9.2-10.7 ribs/mm, in holotype 9.2, with fine spirals in interstices.

Body colour: Ommatophores of preserved specimen bright orange, other soft parts without obvious colouration.

Anatomy (Fig. 27): See genus diagnosis.

Holotype: GHANA: Eastern Region: Atewa Range Forest Reserve, 6.24558[degrees]N 0.54654[degrees]W, 660 m, steep, East-facing slope in upland evergreen forest, 22.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter (RMNH.MOL.123136).

Paratype: 1 specimen, shell fragments, soft parts dissected, same data as holotype (RMNH.MOL.123323).

Other material examined: GHANA: Eastern Region: 1 ad. dry shell, Atewa Range Forest Reserve, plateau in upland evergreen forest, 6.23204[degrees]N 0.57471[degrees]W, 735 m, 22.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter (RMNH.MOL.125937).

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

Habitat: Two live specimens were collected from the understorey vegetation in upland evergreen forest at 660-735 m. Found sympatrically with P atewaensis.

AFRICAN INVERTEBRATES, VOL. 54 (2), 2013

Fig. 26. Pseudavakubia majus sp. n.: (A-E) holotype, RMNH.MOL.123136: apertural (A), lateral (B, C), umbilical (D) and apical (E) views; (F, G) small-sized specimen from Ghana, Atewa Range Forest Reserve, RMNH.MOL.125937, apertural (F) and lateral (G) views. Scale bar = 1 mm.

Remarks: One adult shell with a clearly shorter spire (Figs 26F, G) may have prematurely reached adulthood (shell with developed aperture with barriers and reflected lip), as is suggested by the smaller shell height, smaller number of whorls and less tightly closed umbilicus. Measurements of this specimen are not included in the above description as the specimen may be atypical for the species.

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 6%, 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 1 1/4 whorls distinctly raised above nucleus, providing apex with strongly distorted-acuminate appearance, with very fine spiral sculpture crossed by low growth lines (Fig. 29B), appearing smooth and shining at lower magnification. Later protoconch (ca 3/4 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 midpalatal 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[degrees]N 0.54654[degrees]W, 660 m, 22.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter, steep E-facing 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[degrees]N 0.60445[degrees]W, 655 m, 23.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter, SE-facing 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.

Pseudavakubia ghanaensis de Winter, sp. n.

Fig. 30

Etymology: The species name refers to the country of origin.

Diagnosis: Differs from the similarly sized P atewanensis by the less elongate shell with lower protoconch; peristome proportionally larger and less rounded, with the palatal lip curved in lateral view. The shell of P liberiana is smaller and has less strong apertural dentition. P. majus has a much larger shell.

Description:

Shell (Fig. 30): Small (H 3.3-3.4 mm, holotype 3.3 mm), ovoid-subcylindrical, moderately high-spired, H:D 1.62-1.75, in holotype 1.74, greatest diameter at penultimate whorl. Whorls above widest portion of shell moderately tapering. Whorls 6 1/2-7, moderately convex, whorl increase slow, coiling tightness ca 5.4-5.8, in holotype 5.8. Protoconch diameter 1.04-1.15 mm, of holotype 1.12 mm. Protoconch irregularly coiled with greatly varying whorl width, apex appearing less acuminate than in P. atewanensis. Protoconchs of all shells more or less eroded, obscuring fine details. First 1 1/4 whorl without prominent sculpture, later protoconch (ca 3/4 whorl) with five distant spiral ridges. Transition of smooth to spirally sculptured portion of protoconch abrupt, transition from protoconch to axially ribbed teleoconch somewhat gradual, first 3-4 axial ribs of teleoconch being crossed by spiral cords of protoconch. BWH 41-44% of shell height, in holotype 41%. Periphery of body whorl more or less rounded. Peristome entire, not strongly incrassate, squarish in outline, higher than wide; PH:PW 1.03-1.12, in holotype 1.07, PH 32-36% of H, in holotype 33%, PW 52-55% of D, in holotype 54%. Apertural lip rather wide and flaring. Palatal-basal lip in lateral view curved, arching forward. Angular tooth somewhat protruding, continuing as deeply entering lamella. Tooth on mid-palatal wall strong and pointed. Umbilicus fully closed, umbilical depression with radiating ribs. Teleoconch sculpture consists of slightly oblique, somewhat curved axial ribs, 6.5-9.4 ribs/mm, with fine spirals in interstices.

Body colour: Dried-in soft parts of holotype at least partly red.

Anatomy: Unknown.

Holotype: GHANA: Western Region: Ankasa Conservation area, 5.25411[degrees]N 2.64037[degrees]W, 60 m, 15.i.2010, M.E. Nutsuakor, P. Tattersfield & A.J. de Winter, wet evergreen forest (RMNH.MOL.122857).

Other material examined: GHANA: Central Region: 2 ad. dry shells, Pra Suhien Forest Reserve, 5.34807[degrees]N 1.39002[degrees]W, 230 m, 10.vi.2008, M.E. Nutsuakor & A.J. de Winter, moist evergreen forest (RMNH.MOL. 330215-330216); 1 ad. dry shell, Kakum National Park, 5.3558[degrees]N 1.3925[degrees]W, 220 m, moist evergreen forest along stream, 6.vi.2008, M.E. Nutsuakor & A.J. de Winter (RMNH.MOL.330217).

Distribution (Fig. 31): So far known from south-central and south-western Ghana.

Habitat: All material was collected from leaf-litter on the floor of old secondary lowland (wet and moist) evergreen forest.

Remarks: In P. ghanaensis we provisionally lodge the scanty material (four adult shells, one of which severely damaged) from three localities in central and western Ghana. These shells differ from those of P atewanensis and P liberiana by a comparatively less irregularly coiled protoconch (resulting in a flatter apex which seems less conspicuous distorted in lateral views), a higher than wide peristome, and by a distinctly curved, forward arching palatal lip (in lateral view). In view of the variation in these shells it seems possible that more than one species is involved, and additional material from more localities is needed to assess the variability.

Pseudavakubia liberiana de Winter, sp. n.

Figs 28J-N

Gulella (Avakubia) avakubiensis: Degner 1934b: 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 1% 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 3/4 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[degrees]N 10.06[degrees]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 1934b). 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 CT-scan the absence of internal barriers could be confirmed.

Key to the species of Avakubia and Pseudavakubia

1  Apical whorls regularly increasing in diameter. Internal palatal
   wall of body whorl with shorter or longer fold (externally visible
   by transparency as a pale stripe). Umbilicus open but narrow. Whorl
   increase fast (coiling tightness usually <4.8, rarely 5)
                                                       (Avakubia) 2

-- Apical whorls not regularly increasing in diameter, providing
   protoconch with a distorted appearance. Internal palatal wall of
   body whorl without fold. Umbilicus closed. Whorl increase slow
   (coiling tightness usually >5, but at least 4.9)
                                                  (Pseudavakubia) 10

2  Shell with distinctly acuminate apex and tapering spire (apical
   angle generally < 120[degrees], spire angle <60[degrees])      3

-- Shell apex more rounded, spire aspect less tapering (apical angle
   at least 120[degrees], spire angle >62[degrees])               4

3  Adult shell >5 mm, elongate, apex strongly acuminate, spire
   appearance less tapering; apical angle <100[degrees]. (SW
   Cameroon)                                            A. acuminata

-- Adult shell height at most 4.1 mm, apex less strongly acuminate;
   apical angle >100[degrees]. (SW Cameroon)         A. subacuminata

4  Adult shell >4.7 mm, protoconch very wide and flattened, diameter
   of first two whorls >2.2 mm. (SW Cameroon)           A. semenguei

-- Adult shell <4.3 mm, diameter of first two whorls <1.7mm       5

5  Columellar lamella and palatal fold visible in aperture in
   oblique view. Shell appearing smooth or with little pronounced and
   very close-set ribs. Spirals on protoconch not prominent.
   (Bioko I.)                                   A. ortizdezarateorum

-- Columellar lamella and palatal fold not visible in aperture; ribs
   strong and more distant, spirals on protoconch prominent       6

6  Protoconch whorls strongly convex; axial ribs distant (ca 8
   ribs/mm on penultimate whorl); shell height <3.5 mm; apical angle
   about 120[degrees]. (Eastern DRC & Uganda)        A. avakubiensis

-- Protoconch whorls less convex; axial ribs closer               7

7  Shell ribbing dense (ca 11-13 ribs/mm on penultimate whorl)    8

-- Ribs less close-set (ca 9-10 ribs/mm on penultimate whorl)     9

8  Shell small (shell height <3.5 mm); body whorl >50% of shell
   height. (SW Cameroon)                              A. fruticicola

-- Shell larger (shell height >3.6 mm), body whorl <50% of shell
   height. (NW Gabon)                                  A. crystallum

9  Shell height 3.8-4.0 mm, shell width 2.1-2.3 mm, about 10 ribs/mm
   on penultimate whorl. (Bioko I.)                    A. biokoensis

-- Shell height 3.2-3.6 mm, shell width 1.9-2.0 mm, about 9 ribs/mm
   on penultimate whorl. (Ghana)                     A. occidentalis

10 Shell comparatively large and cylindrical, shell height
   generally >4 mm. Protoconch width 1.4-1.6 mm. Coiling tightness ca
   5                                                        P. majus

-- Shell height 2.9-3.4 mm. Protoconch width not exceeding 1.3 mm.
   Coiling tightness >5.4                                          11

11 Apertural lip in lateral view strongly curved and arching
   forward. Peristome higher than wide. (Ghana)         P. ghanaensis

-- Apertural lip in lateral view comparatively straight, not arching
forward. Peristome as wide as high or wider than high              12

12 Shell height <3 mm. Palatal tooth very weak. Last whorl 45% of
   shell height. (Liberia)                               P. liberiana

-- Shell height >3.3 mm. Palatal tooth prominent, pointed. Last
   whorl <40% of shell height. (Ghana)                     P. atewana


DISCUSSION

Diversity and systematics

The present study has revealed the genus Avakubia to be considerably more speciose than previously known, with at least nine species instead of two. The resulting classification is largely based on shell characters of a limited number of specimens per species. Nevertheless, we think the recognised species are not geographic variants of a small number of widespread species. The sympatric occurrence of four Avakubia taxa within a 1500 [km.sup.2] area in Southwest Cameroon (see de Winter & Gittenberger 1998: fig. 1), one of the few malacologically better sampled areas in western Africa, supported the evaluation of species limits in this area, and assisted in the interpretation of conchological differences in other populations, in addition to multivariate statistical analysis of shell measurements. Alcohol-preserved material needed to confirm the taxonomic conclusions of this study by molecular data is either not available at this stage, or too scarce and probably too old. Molecular data should be used to test the species hypotheses once sufficient fresh material has been collected. The nine Avakubia species recognised, represented by only 105 adult specimens, come from a tiny portion of the potential range of the genus; from huge areas in tropical Africa no Avakubia material has as yet been reported (Fig. 3). The presence of still more undescribed species seems therefore likely. Future use of molecular data may reveal additional cryptic species, the existence of which has been suspected in this study in a few instances (e.g. in A. subacuminata).

At the first glance, Avakubia (and Pseudavakubia) species share surprisingly characteristic shells that readily separate them from other Gulella-like streptaxids, resembling more or less closely the description and illustration of the type species A. avakubiensis by Pilsbry (1919). Later records in the literature of the type species from a huge part of Equatorial Africa are found to actually embrace five additional morphospecies, which are all described in this paper as new species with much more restricted distributions; one of these actually belongs to Pseudavakubia. In addition, three Avakubia species (A. acuminata, A. semenguei and A. ortizdezarateorum) with more distinctive shells are recognised. The first two occur sympatrically with A. fruticicola in the same microhabitat, leaving open the possibility of character displacement as a cause of their deviating shell morphology. The atypical shell sculpture and apertural dentition of A. ortizdezarateorum may suggest a different generic position. However, in the absence of information on the soft parts, this species is provisionally retained in Avakubia.

The type species of Avakubia was described on the basis of a limited set of shell characters, like the beaded spiral sculpture on the protoconch, the teleoconch sculpture of axial ribs with spiral lines in the interstices, the presence of only a few barriers in the aperture and the biconical shell shape with the greatest width above the body whorl (Pilsbry 1919). In the present study we have found that the available material is not homogenous and cannot be attributed to a single genus, although all shells conform to the description of Avakubia provided by authorities like Thiele (1933), Degner (1934b) and Schileyko (2000). These authors did not explicitly refer to the granular nature of the apical spirals, although this character was mentioned in the original description. Likewise, the presence of a deep-set palatal fold was not indicated. Pilsbry (1919) mentioned the presence of "a low, transverse fold [is] visible some distance within the basal margin", an unclear and easily misinterpreted description, and the character is not visible in the original shell drawing. In later treatments the palatal fold was only mentioned by Ortiz de Zarate and Ortiz de Zarate Rocandio (1956).

The discovery of four species with non-granular apical spirals and lacking the palatal fold (and other features) prompted the erection of the new genus Pseudavakubia. Many shell characters typical of Avakubia are shared by members of Pseudavakubia. It is therefore not surprising that Degner (1934b: 377), a sharp observer and competent malacologist, was quite certain about the correct identification of his Liberian specimen of "Gulella (Avakubia) avakubiensis" (described in the present paper as Pseudavakubia liberiana): "Die Art ist so trefflich gekennzeichnet dass Verwechselungen unmoglich erscheinen" [the species is so characteristic that mistakes seem to be impossible]. The identity of Degner's unfigured shell only became clear after study of the unique specimen.

The cryptic palatal fold is potentially a synapomorphy supporting the monophyly of the genus Avakubia. In this position the structure is not known in other Streptaxidae (exclusive of streptaxomorph taxa), where palatal folds, if present, are readily visible in the aperture and generally have corresponding external depressions on the back of the shell. The beaded spiral sculpture on the protoconch appears to be unknown among other Streptaxidae. Various streptaxid species have spiral sculpture on the protoconch, but of most species this has not been studied in sufficient detail. Unique characters for Pseudavakubia may be the irregularly coiled protoconch consisting of two sharply demarcated and differently sculptured portions, followed by a regularly coiled teleoconch. The genital anatomy of both Avakubia and Pseudavakubia are superficially not dissimilar. The systematic importance of the observed differences could not be assessed due to small number of dissected specimens and species. The most conspicuous difference is that in Pseudavakubia no trace of a lateral penial caecum has been observed. Pseudavakubia may be related to one of the West African streptaxid radiations that have been assigned to either Gulella s.l. or Ptychotrema L. Pfeiffer, 1853 s.l., the soft parts morphology of which are largely unknown. Whilst speculating about phylogenetic affinities, it should be kept in mind that the knowledge of the land snails, including Streptaxidae, of West and Central Africa is rather imperfect. Additional, especially live collected, streptaxid material is needed to address these questions.

Although we are convinced that Avakubia and Pseudavakubia represent separate taxa, each with a number of species sharing a distinctive set of characters, it remains unclear whether they are related, or even part of a monophyletic clade, as would be suggested by the remarkable similarities in shell size, shape and teleoconch sculpture. The fact that representatives of both genera share the absence of chitinous hooks and spines in the penis provides the strongest support for a close relationship. This is an uncommon character within the Streptaxidae, but not a unique one, however (Schileyko 2000; Sutcharit et al. 2010). According to Sutcharit et al. (2010) chitinized penial structures are fully absent in Careoradula Gerlach & van Bruggen, 1999, Impertubaria constans (von Martens & Wiegman, 1898), Diaphera Albers, 1850 and Discartemon L. Pfeiffer, 1856 (actually, only the genital anatomy of D. stenostomus van Benthem Jutting, 1954, appears to be known, not that of the type species D. discus (L. Pfeiffer, 1851), see Berry (1965)). Sutcharit et al. (2010) separated Diapheridae as an independent early offshoot from the Streptaxidae on the basis of molecular characters of Diaphera prima Panha, 2010, a species from Thailand attributed to the genus (the type species of Diaphera, D. cumingiana (L. Pfeiffer, 1845) from the Philippines is only known by its shell). These authors considered the absence of penial armature in D. prima a plesiomorphic condition. Rowson et al. (2011) retained A. avakubiensis as a basal taxon within the Streptaxidae on the basis of molecular data, so the penial armature may have evolved in the Streptaxidae s.l. after the origin of a clade including both Avakubia and Pseudavakubia, but may also have been lost independently in these taxa. Too few Streptaxidae taxa are anatomically and molecularly known to infer phylogenetic conclusions from this character.

In a specimen of A. acuminata a spermatophore-like structure was found inside the lower penis. This appears to be the third record of a spermatophore in a species of Streptaxidae, after reports in Sinistrexcisa de Winter, Gomez & Prieto, 1999, and Dadagulella Rowson & Tattersfield, 2013 (de Winter et al. 1999; Rowson & Tattersfield 2013). As was recently discussed by Rowson and Tattersfield (2013), it remains to be proven that such structures are true spermatophores. The location in the male genitalia of Avakubia where a spermatophore could be produced is unclear; a possibility may be the dilated, muscular portion of the vas deferens shortly before it enters the penis, which may then be termed epiphallus.

Ecology and conservation

Only some 150 Avakubia specimens, juvenile shells included, were worldwide available for this study. Various factors possibly contribute to this apparent scarcity, alone or in combination, as discussed below.

Insufficient collecting in Central Africa is no doubt a major cause of the paucity of material. Most recent Avakubia material was obtained by litter sieving methods (de Winter 1995 and unpubl. data; Fontaine et al. 2007; Wronski & Hausdorf 2010; Tattersfield, pers. comm.), or by beating the understorey vegetation over an umbrella (de Winter & Gittenberger 1998). Large areas of tropical Africa have not been surveyed at all as regards molluscs, let alone by these labour-intensive methods; especially the latter method is not commonly employed by malacologists. Three out of four Avakubia species found in Southwest Cameroon were exclusively collected from the understorey vegetation; a fourth species was mostly found on the forest floor. Neglect of the arboreal habitat might explain, for example, the marginal occurrence of Avakubia in Lope National Park in Gabon (Fontaine et al. 2007), where in total only three shells were obtained from two litter samples out of 100 systematically litter-sampled forest plots.

Avakubia species appear to be largely confined to rainforests. In Africa such forests usually grow mostly on nutrient-poor, acidic soils (e.g. Showers 2006 and references therein) where snail abundance is low. In addition, land snails in tropical forests tend to have quite small ranges or at least very patchy distributions (Solem 1984; Schilthuizen 2011).

Most specimens for which habitat data are available, were collected from little disturbed forest sites. One species (A. subacuminata) was observed in both undisturbed forest and anthropogenic habitat (cocoa plantation and young secondary forest on abandoned field), but lack of records from disturbed habitat may be due to sampling bias.

Undisturbed rainforests in Africa are rapidly disappearing. The arboreal species may depend on a stratified vegetation, as present in such forests. Also in view of the apparently small ranges of various Avakubia species, at least some species are likely to be threatened, together with many other African rainforest-dwelling land snail species. One example is A. acuminata. An intensively studied 1 [km.sup.2] area in Southwest Cameroon yielded 34 specimens, i.e. 1.3% of all land snail specimens found there (de Winter & Gittenberger 1998). This species was not encountered in some plots a few kilometres away from this km area, nor in two areas 20-30 km away with similar forest habitat, which were studied using the same collection effort and techniques, yielding only other Avakubia species. The Pseudavakubia species may be even more vulnerable, given the rapid deforestation of the upper Guinea forest area, but as yet very little is known of their distribution. Especially P atewana and P majus inhabiting the threatened Atewa Range in Ghana (McCullough et al. 2007) may be endangered.

ACKNOWLEDGEMENTS

We are indebted to the following persons for the loan of material under their care: Rafael Araujo, Museo Nacional de Ciencias Naturales, Madrid; Adam Baldinger (Museum of Comparative Zoology, Cambridge Mass.); Benoit Fontaine (Museum National d'Histoire Naturelle, Paris), Matthias Glaubrecht (Museum fur Naturkunde Berlin), Bernhard Hausdorf (Zoologisches Museum der Universitat Hamburg), Rose Sablon and Jackie Van Goethem (Royal Belgian Institute of Natural Sciences, Brussels). Peter Tattersfield made his specimens from Uganda available. Christine Johnson (American Museum of Natural History, New York) kindly made an effort to find the type of A. avakubiensis. Mac Elikem Nutsuakor (Kumasi, Ghana) participated in fieldwork in Ghana in 2008, and he and Peter Tattersfield took part in fieldwork in Ghana in 2010. Field work by the first author in Cameroon was assisted by Eric-Joel Semengue. Field work in Cameroon in 1995 and 1996 was funded by the Netherlands Foundation for the Advancedment of Tropical Research (NWO-WOTRO). The first author is indepted to Prof. S.K. Oppong (KNUST, Kumasi, Ghana) for his general support of malacological work in Ghana, and for greatly facilitating field work in Ghana in 2010 by providing a 4WD vehicle with a driver, Simpson Ansong, who also actively participated in snail collecting. Erik-Jan Bosch (Naturalis) prepared Fig. 1 and all the distribution maps. Bas Blankenvoort (Naturalis) prepared Fig. 2 and drew Figs 6, 15, and 27. Dirk van der Marel (Naturalis) provided technical assistance with micro-CT and low-vacuum SEM. This paper benefitted from the constructive comments of Heike Kappes, Igor Muratov and Ben Rowson.

REFERENCES

Berry, A.J. 1965. The genital systems of Discartemon stenostomus van Benthem Jutting and Huttonella bicolor (Hutton) (Pulmonata: Streptaxidae) from Malaya. Proceedings of the Malacological Society of London 36: 221-228.

Bruggen, A.C., van. 1973. Papers on African non-marine molluscs by Ortiz de Zarate. Achatina 4: 83-84.

Bruggen, A.C., van & Van Goethem, J.L. 1997. Dr. William Adam's iconography of Central and West African Gulella species (Gastropoda Pulmonata: Streptaxidae). Part 1: nominal taxa. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Biologie 67: 5-30.

Connolly, M. 1928. The non-marine Mollusca of Sierra Leone. Annals and Magazine of Natural History, including Zoology, Botany, and Geology, Ser. 10 1: 529-551, pl. 18.

Degner, E. 1934a. Westafrikanische Landschnecken. I. Streptaxiden, Helicarioniden, Vaginuliden. Zoologische Jahrbucher (Systematik) 65: 209-308.

--1934b. Streptaxiden aus Liberia. Revue de Zoologie et de Botanique Africaines 24: 369-379.

Eardley, C.D. 2004. Taxonomic revision of the African stingless bees (Apoidea: Apidae: Apinae: Meliponini). African Plant Protection 10: 63-96.

Emberton, K.C. 2001. Dentate Gulella of Madagascar (Pulmonata: Streptaxidae). American Malacological Bulletin 16: 71-129.

Fontaine, B., Gargominy, O. & Neubert, E. 2007. Land snail diversity of the savanna/forest mosaic in Lope National Park, Gabon. Malacologia 49: 313-338.

Hammer, 0., Harper, D.A.T. & Ryan, P.D. 2001. PAST: paleontological statistics software package for education and data analysis. Palaeontologia electronica 4: 1-9. (http://folk.uio.no/ohammer/past)

Kerney, M.P. & Cameron, R.A.D. 1979. A field guide to the land snails of Britain and north-west Europe. London: Collins.

McCullough, J., Alonso, L., Naskrecki, P. & Osei-Owusu, Y., eds. 2007. A rapid biodiversity assessment of the Atewa Range Forest Reserve, Ghana. RAP Bulletin of Biological Assessment 47: 1-193.

Ortiz de Zarate Lopez, A. & Ortiz de Zarate Rocandio, A. 1956. Contribuciones al conocimiento de la fauna malacologica terrestre de la isla de Fernando Poo. II. Familia Streptaxidae. Boletin de Real SociedadEspanola de Historia Natural 53: 75-140.

Pilsbry, H.A. 1919. A review of the land Mollusks of the Belgian Congo chiefly based on the collections of the American Museum Congo Expedition, 1900-1915. Bulletin of the American Museum of Natural History 40: 1-370.

Rowson, B. & Tattersfield, P. 2013. Revision of Dadagulella gen. n., the "Gulella radius" group (Gastropoda: Streptaxidae) of the eastern Afrotropics, including six new species and three new subgenera. European Journal of Taxonomy 37: 1-46.

Rowson, B., Tattersfield, P. & Symondson, W.O.C. 2011. Phylogeny and biogeography of tropical carnivorous land-snails (Pulmonata: Streptaxoidea) with particular reference to East Africa and the Indian Ocean. Zoologica Scripta 40: 85-98.

Schileyko, A.A. 2000. Treatise on Recent terrestrial pulmonate molluscs. Part 6: Rhytididae, Chlamydephoridae, Systrophiidae, Haplotrematidae, Streptaxidae, Spiraxidae, Olecinidae, Testacellidae. Ruthenica Supplement 2: 731-880.

Schilthuizen, M. 2011. Community ecology of tropical forest snails: 30 years after Solem. Contributions to Zoology 80: 1-15.

Showers, K.B. 2006. A history of African soil: Perceptions, use and abuse. In: McNeill, J.R. & Winiwarter, V., eds, Soils and societies. Perspectives from environmental history. Isle of Harris, UK: The White Horse Press, pp. 118-176.

Solem, A. 1984. A world model of land snail diversity and abundance. In: Solem, A. & van Bruggen, A.C., eds, Word-wide snails. Biogeographical studies on non-marine Mollusca. Leiden, The Netherlands: Brill, pp. 6-22.

Sutcharit, C., Naggs, F., Wade, C.M., Fontanilla, I. & Panha, S. 2010. The new family Diapheridae, a new species of Diaphera Albers from Thailand, and the position of the Diapheridae within a molecular phylogeny of the Streptaxoidea (Pulmonata: Stylommatophora). Zoological Journal of the Linnean Society 160: 1-16.

Thiele, J. 1933. Die von Oskar Neumann in Abessinien gesammelten und einige andere afrikanische Landschnecken. Sitzungsberichte der Gesellschaft naturforschender Freunde zu Berlin 1933: 280-323.

Verdcourt, B. 1962. Preliminary keys for the identification of the species of the genus Gulella Pfr. occuring in East Africa. AnnalesMuseeRoyal de l'Afrique Centrale 8: 1-39.

--1984. Discontinuities in the distribution of some East African land snails. In: Solem, A. & van

Bruggen, A.C., eds, Word-wide snails. Biogeographical studies on non-marine Mollusca. Leiden, The Netherlands: Brill, pp. 134-155.

Villena, M., Aparicio, M.T., Baratech, L. & Templado, J. 1997. Los "ejemplaros typo" de las colecciones malacologicas del Museo Nacional de Ciencias Naturales. Volumen II. Monografias delMuseo Nacional de Ciencias Naturales 11: 1-170, pls 1-3.

Winter, A.J. de. 1995. Gastropod diversity in a rain forest in Gabon, West Africa. In: van Bruggen, A.C., Wells, S.M. & Kemperman, Th.C.M., eds, Biodiversity and conservation of the Mollusca. Oegstgeest-Leiden, The Netherlands: Backhuys, pp. 223-228.

Winter, A.J. de & Gittenberger, E. 1998. The land snail fauna of a square kilometer patch of rainforest in southwestern Cameroon: high species richness, low abundance, and seasonal fluctuations. Malacologia 40: 231-250.

Winter, A.J. de, Gomez, B.J. & Prieto, C.E. 1999. Sinistrexcisa, a new genus of land snail from Central West Africa with four new species (Gastropoda: Pulmonata: Streptaxidae). Journal of Molluscan Studies 65: 209-221.

Wronski, T. & Hausdorf, T. 2010. Diversity and body-size patterns of land snails in rain forests in Uganda. Journal of Molluscan Studies 76: 87-100.

A. J. de Winter * and N. Vastenhout Netherlands Center for Biodiversity Naturalis, P. O. Box 9517, 2300 RA Leiden, The Netherlands; Ton.dewinter@naturalis.nl

* Corresponding author

TABLE 1

Conchometric data for 87 adult Avakubia shells. Measurements and
abbreviations are explained in Fig. 1. Measurements of holotype
of A. avakubiensis are taken from available illustrations (see
species description), as far as possible (*-holotype excluded,
?-character not observable in available illustrations).

Shell heigth (mm)

Species                  Holotype    mean       range      No.

A. acuminata               5.4       5.4       5.1-5.8      21
A. avakubiensis           ca 3.2    3.3 *     3.0-3.5 *    16 *
A. cf.                                           3.2        1
avakubiensis [Gabon]

A. biokoensis              3.8       3.9       3.8-4.0      4
A. crystallum              3.6       3.7       3.6-3.8      2
A. fruticicola             3.1       3.3       3.1-3.5      16
A. occidentalis            3.6       3.3       3.2-3.6      3
A. ortizdezarateorum       3.0        3        2.9-3.1      5
A. semenguei               4.8       4.9       4.7-5.1      5
A. subacuminata            3.8       3.8       3.5-4.1      14
Shell diameter (mm)

Species                  Holotype    mean       range      No.

A. acuminata               2.7       2.7       2.7-2.8      21
A. avakubiensis           ca 1.9    1.9 *     1.9-2.0 *    16 *
A. cf.                                           2.0        1
avakubiensis [Gabon]
A. biokoensis              2.1       2.2       2.1-2.3      4
A. crystallum              2.0       2.0       2.0-2.1      2
A. fruticicola             1.9       1.9       1.8-2.0      16
A. occidentalis            2.0       2.0       1.9-2.0      3
A. ortizdezarateorum       1.8       1.7       1.7-1.8      5
A. semenguei               2.9       2.9       2.8-3.0      5
A. subacuminata            2.1       2.2       2.1-2.2      14
Number of whorls

Species                  Holotype    mode       range      No.

A. acuminata                6%        6%        6%-7        21
A. avakubiensis             ?         5%        5-5%       16 *
A. cf.                                           5%         1
avakubiensis [Gabon]

A. biokoensis               6         6           6         4
A. crystallum               5%        5%         5%         2
A. fruticicola              5         5         5-5%        16
A. occidentalis             5%        5%        5-5%        3
A. ortizdezarateorum        5         5           5         5
A. semenguei                5         5         5-5%        5
A. subacuminata             6%        6%         6-7        14
Peristome height (mm)

Species                  Holotype    mean       range      No.

A. acuminata               1.64      1.76     1.56-1.93     21
A. avakubiensis             ?        1.14     1.05-1.23    16 *
A. cf.                                          1.04        1
avakubiensis [Gabon]

A. biokoensis              1.38      1.42     1.38-1.45     4
A. crystallum              1.32      1.25     1.18-1.32     2
A. fruticicola             1.15      1.22     1.04-1.28     16
A. occidentalis            1.24      1.11     0.97-1.24     3
A. ortizdezarateorum       0.97      0.96     0.89-1.01     5
A. semenguei               1.93      1.90     1.86-1.94     5
A. subacuminata            1.20      1.17     1.04-1.22     14
Peristome width (mm)

Species                  Holotype    mean       range      No.

A. acuminata               1.49      1.50     1.30-1.66     21
A. avakubiensis             ?       1.04 *   0.97-1.14 *   16 *
A. cf.                                          1.09        1
avakubiensis [Gabon]

A. biokoensis              1.23      1.24     1.20-1.29     4
A. crystallum              1.15      1.09     1.09-1.15     2
A. fruticicola             1.04      1.11     1.04-1.22     16
A. occidentalis            1.17      1.09     1.02-1.17     3
A. ortizdezarateorum       0.88      0.87     0.77-0.95     5
A. semenguei               1.67      1.64     1.60-1.72     5
A. subacuminata            1.10      1.10     1.0-1.23      14
Body whorl height (mm)

Species                  Holotype    mean       range      No.

A. acuminata               2.27      2.41     2.25-2.56     21
A. avakubiensis             ?       1.59 *   1.51-1.76 *   16 *
A. cf.                                           1.5        1
avakubiensis [Gabon]

A. biokoensis              1.83      1.84     1.79-1.93     4
A. crystallum              1.78      1.77     1.77-1.78     2
A. fruticicola             1.75      1.71     1.63-1.86     16
A. occidentalis            1.75      1.64     1.51-1.64     3
A. ortizdezarateorum       1.40      1.38     1.34-1.46     5
A. semenguei               2.56      2.55     2.53-2.60     5
A. subacuminata            1.57      1.58     1.43-1.73     14
Apical angle (degrees)

Species                  Holotype    mean       range      No.
A. acuminata                90        95        89-97       21
A. avakubiensis           ca 122    120 *     115-132 *    16 *
A. cf.                                           116        1
avakubiensis [Gabon]

A. biokoensis              129       133       129-136      4
A. crystallum              125       123       120-125      2
A. fruticicola             140       136       128-144      16
A. occidentalis            126       127       126-129      3
A. ortizdezarateorum       133       132       124-140      5
A. semenguei               144       142       134-146      5
A. subacuminata            110       113       107-122      14
Diameter of
1st whorl (mm)

Species                  Holotype    mean       range      No.

A. acuminata               0.78      0.78     0.67-0.85     21
A. avakubiensis             ?        0.75     0.68-0.83    16 *
A. cf.                                          0.84        1
avakubiensis [Gabon]

A. biokoensis              0.72      0.83     0.72-0.94     4
A. crystallum              0.9       0.9         0.9        2
A. fruticicola             0.83      0.82     0.71-0.95     16
A. occidentalis            0.86      0.84     0.82-0.86     3
A. ortizdezarateorum       0.86      0.87     0.84-0.91     5
A. semenguei               1.39      1.30     1.22-1.39     5
A. subacuminata            0.71      0.73     0.67-0.78     14
Diameter of 1st +
2nd whorl (mm)

Species                  Holotype    mean       range      No.

A. acuminata               1.44      1.45     1.32-1.69     21
A. avakubiensis             ?        1.30     1.21-1.41    16 *
A. cf.                                          1.34        1
avakubiensis [Gabon]

A. biokoensis              1.28      1.40     1.25-1.64     4
A. crystallum              1.47      1.49     1.47-1.50     2
A. fruticicola             1.46      1.44     1.29-1.64     16
A. occidentalis            1.44      1.44     1.36-1.51     3
A. ortizdezarateorum       1.39      1.43     1.34-1.48     5
A. semenguei               2.32      2.19     2.10-2.32     5
A. subacuminata            1.26      1.24     1.14-1.30     14
RD5 (mm)

Species                  Holotype    mean       range      No.

A. acuminata               0.75      0.77     0.65-0.94     21
A. avakubiensis             ?       0.74 *   0.67-0.83 *   16 *
A. cf.                                           0.7        1
avakubiensis [Gabon]

A. biokoensis              0.55      0.59     0.55-0.61     4
A. crystallum              0.56      0.55     0.54-0.56     2
A. fruticicola             0.52      0.53     0.47-0.56     16
A. occidentalis            0.67      0.63     0.60-0.67     3
A. ortizdezarateorum                           < 0.25       5
A. semenguei               0.52      0.58     0.52-0.69     5
A. subacuminata            0.87      0.79     0.64-0.91     14
Spire angle (degrees)

Species                  Holotype    mean       range      No.

A. acuminata                51        53        49-57       21
A. avakubiensis           ca 71      67 *      61-75 *     16 *
A. cf.                                           65         1
avakubiensis [Gabon]

A. biokoensis               65        64        61-66       4
A. crystallum               67        66        65-67       2
A. fruticicola              73        72        67-77       16
A. occidentalis             63        68        63-73       3
A. ortizdezarateorum        68        65        63-68       5
A. semenguei                75        73        71-76       5
A. subacuminata             59        58        51-62       14

TABLE 2

Loadings of 11 shell characters (Fig. 1) of 87 Avakubia shells on
the first three principle component axes, and the percentage of
the variation in the data explained by the axes.

                 Axis 1    Axis 2    Axis 3

% variation       62.2      24.1       9.3
accounted for
Character
loadings:

W                 0.1765   -0.1684   -0.2918
H                 0.4259    0.1128   -0.2401
D                 0.3187    0.1204   -0.0299
AA               -0.2060    0.1645    0.3668
DW1               0.0147    0.3831    0.3455
DW2               0.0856    0.3607    0.3022
PH                0.4116    0.2448    0.0074
PW                0.4327   -0.6825    0.5732
SA               -0.1651    0.1285    0.4217
BWH               0.3694    0.2511    0.0096
RD                0.4327   -0.6825    0.5732
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Article Details
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Title Annotation:p. 635-663
Author:de Winter, A.J.; Vastenhout, N.
Publication:African Invertebrates
Article Type:Report
Geographic Code:60AFR
Date:Dec 1, 2013
Words:10391
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