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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).

INTRODUCTION

Avakubia is a rather poorly known taxon of the family Streptaxidae of small (ca 3-6 mm) and apparently uncommon land snails that inhabit the forests of equatorial Africa. Avakubia was introduced as a section of the genus Gulella Pfeiffer, 1856, by Pilsbry (1919) for a single shell of Gulella (Avakubia) avakubiensis Pilsbry, 1919 from the Ituri Forest in the eastern Democratic Republic of the Congo (formerly Belgian Congo, Zaire). The only other formally named Avakubia species, G. (A.) acuminata Thiele, 1933, was described from a single specimen from Cameroon. The taxon was defined on the basis of a few shell characters, namely a spirally sculptured protoconch, a teleoconch with regularly spaced axial ribs and spiral lines in the interstices, a biconical shell shape, and a paucidentate aperture (Pilsbry 1919). Although all these characters individually occur in other streptaxid (sub)genera, Avakubia representatives were generally thought to be fairly typical (Degner 1934b). Schileyko's (2000) description of the genus is partly faulty, presenting the genital anatomy of Gulella dautzenbergi Connolly, 1928, copied from Degner (1934a), as representative for the (sub)genus. However, G. dautzenbergi clearly does not belong to Avakubia, lacking typical characters for the genus, such as the spiral sculpture on the apex (see Connolly 1928; Degner 1934a), and belongs to a rather different streptaxid radiation. Recent molecular work by Rowson et al. (2011) indicates that A. avakubiensis is not related to the genus Gulella and even occupies a basal position within the Streptaxidae. In the present study, Avakubia is for the first time treated as an independent genus.

Still, the delimitation of the genus Avakubia is rather unclear. Nothing has as yet been published on the anatomy. The two species described to date, A. avakubiensis and A. acuminata, are quite different in shell size and shape, and the erroneous assignment of Gulella dautzenbergi to Avakubia in an authoritative treatise (Schileyko 2000) underlines the need to critically define the boundaries of the genus.

The genus Avakubia appears to be confined to equatorial Africa, but available records are scarce. After the description of A. avakubiensis in 1919, a second specimen was recorded from Liberia (Degner 1934b). More than two decades later the species was reported from localities on the Isle of Fernando Poo, now Bioko Island, Equatorial Guinea (Ortiz de Zarate Lopez & Ortiz de Zarate Rocandio 1956). Verdcourt (1962) published a record from Uganda. Since the mid-1990's, additional records (albeit sometimes with tentative identifications) have been published from Gabon (de Winter 1995), Cameroon (de Winter & Gittenberger 1998), Democratic Republic of the Congo (van Bruggen & Van Goethem 1997) and Uganda (Wronski & Hausdorf 2010). Verdcourt (1984) mentioned G. (A.) avakubiensis as one of the few land snail species with a range extending all across the African equatorial forest belt ("the Fernando Poo--Cameroun--Zaire--western Kenya route"). This species has a published linear range of ca 4750 km across continental Africa. In contrast, A. acuminata has been recorded only once since its description, again from Cameroon (de Winter & Gittenberger 1998). Some studies have indicated the existence of additional Avakubia species (de Winter & Gittenberger 1998; Fontaine et al. 2007), but these have so far not been formally described.

The present paper offers a taxonomic revision of all available Avakubia specimens based on the morphology of the shell as well as, as far as available, of the soft parts. We address the question whether the material attributed to Avakubia in the literature and in unpublished collections constitutes a monophyletic grouping; this is not a phylogenetic study, however. The available material is too scanty, incomplete and partly too old to undertake a molecular study at this stage. In this paper we also addresses the biogeographically interesting question whether all records of A. avakubiensis in the literature indeed refer to a single, very widespread, species. The reported distribution seems at odds with Solem's (1984) assertion that most land snail species have a linear range of tens or perhaps hundreds of kilometres, but not one stretching over nearly 5000 km between the Liberian and Ugandan localities. Such a large range would be particularly surprising for a rainforest-dwelling species that is unlikely to have benefitted from human activities.

MATERIAL AND METHODS

The following collection acronyms have been used:

AMNH--American Museum of Natural History, New York, USA;

MCZ--Museum of Comparative Zoology Harvard University, Cambridge, Mass., USA;

MNHN--Museum National d'Histoire Naturelle, Paris, France;

DE WINTER & VAS1ENHUU1: REV1S1UN UF AVAKUdIA

MNCN--Museo Nacional de Ciencias Naturales, Madrid, Spain;

NMW--National Museum of Wales, Cardiff, UK;

PT--collection of Peter Tattersfield, UK (to be deposited in NMW);

RBINS--Royal Belgian Institute of Natural Sciences, Brussels, Belgium;

RMNH--Naturalis Biodiversity Center, formerly Rijksmuseum van Natuurlijke Historie, Leiden, The Netherlands;

ZMB--Museum fur Naturkunde, Humboldt University Berlin, Germany;

ZMH--Zoological Museum, University of Hamburg, Germany.

Other abbreviations used throughout the paper:

AA--apical angle;

ad.--adult;

BWH--height of body whorl;

D--shell diameter;

DRC--Democratic Republic of the Congo (Belgian Congo, Zaire);

DW1--diameter of first whorl;

DW2--diameter of first two whorls;

H--shell height;

juv.--juvenile;

PH--peristone height;

PW--peristome width;

RD--width of five consecutive interstices (thus embracing six ribs) in the middle of the penultimate whorl;

SA--spire angle

SEM--scanning electron microscopy;

sta.--station:

W--number of whorls.

We made an attempt to examine all Avakubia material reported in the literature, in addition to unpublished material attributed to Avakubia in museum collections and some recently collected material. 1n total, we have been able to examine some 151 specimens, of which 114 are adult shells. Apart from the holotype of A. acuminata (ZMB), previously published voucher material could be studied from Cameroon (RMNH), DRC (RB1NS), Bioko 1. (formerly Fernando Poo; MNCN, RB1NS, RMNH), Gabon (MNHN, RMNH), Liberia (MCZ), and Uganda (ZMH). The holotype of A. avakubiensis could not be traced in AMNH (Dr Christine Johnson, pers. comm., Dec. 2011), but a photograph of the holotype shell in frontal view is available on http://research.amnh.org/iz/types_db/ details.php?specimen_id=9951. Schileyko (2000) provided an accurate drawing of the holotype in frontal view. Specimens reported from the northern DRC (van Bruggen & Van Goethem 1997) were not available, as was the material published by Verdcourt (1962) from Entebbe, Uganda. Unpublished samples identified as Avakubia were studied from Uganda (PT), Cameroon (RMNH), Gabon (RMNH) and Ghana (RMNH, PT). The geographic distribution of the studied specimens is very uneven; a large proportion of the material (including 55 adult specimens) was collected within an area of ca 1500 km2 in Southwest Cameroon by the senior author.

All shells were studied under a Leica M165c stereo microscope and sorted to tentative morphospecies taking qualitative characters like approximate size, shape and sculpture into account. Ten shell measurements (Fig. 1) were made on images of adult shells taken with a Leica DFC420 digital camera attached to the stereo microscope, using Leica LAS 2.8.1 software, and the number of whorls of each shell was counted according to Kerney and Cameron (1979) and rounded to the nearest quarter whorl. Each shell was mounted, photographed and measured twice in frontal and apical view, and the mean of both measurements was taken unless strongly deviating values could be attributed to measurement errors. Axial rib density on the teleoconch was measured as the distance of five interstices between six consecutive ribs, measured parallel to the sutures in the centre of the penultimate whorl. In species descriptions, shell measurements are often expressed as ratio's, like H:D, BWH:H, PH:H, PW:D, #ribs/mm and W:InH (coiling tightness, Emberton 2001).

[FIGURE 1 OMITTED]

Measurement data were analysed by a principal component analysis (PCA) after log transformation to roughly equalize variances. The resulting grouping based on measurement data was compared with an initial tentative morphospecies assignment (which also took qualitative characters into account), and a preliminary classification of taxa was made. A MANOVA was done to test the significance of the overall difference between the pre-determined morphospecies. A canonical variate analysis (CVA) was done in order to maximize the difference between the groups in a multivariate space. Distinction between pairs of species was tested in a pairwise Hotelling's test. However, since the distribution of the measurements appeared not to be multivariately normal, this may not be a correct procedure. Equality of the means of sets of multivariate data of any combination of two morphospecies was therefore also tested by a non-parametric twogroup permutation test using the Mahalanobis squared distance measure. Since the latter test resulted in higher significance levels of distinction between pairs of species than the pairwise Hotelling's test, the latter test was used to provide at least an indication of the degree of difference between pairs of species. All statistical analyses were performed using the free software program PAST (Hammer et al. 2001).

Qualitative characters used in species description include: colour of the soft parts (reddish or pale) based on field notes and/or from the colour of dried-in soft parts visible through the shell, protoconch shape, protoconch sculpture, teleoconch sculpture (other than rib distance), umbilical development, peristome development, overall shell shape, whorl convexity, as well as the arrangement of barriers in the aperture and deeper within the body whorl (see below). The protoconch sculpture was studied by SEM, using a Jeol 6480LV, for which most examined shells were coated, others (especially type specimens) were studied uncoated in low-vacuum. The latter method resulted in less clear pictures. The alcohol-preserved material was mostly contracted and withdrawn in the upper whorls. In view of the scantiness of Avakubia specimens available, only few specimens were dissected since study of the soft parts inevitably involved destruction of the shell. We became particularly hesitant to sacrifice more alcohol-preserved specimens, after several animals of A. acuminata and A. fruticicola with fully developed shells were found to have rather juvenile genitalia still. Genitalia were studied in alcohol at up to 75* magnification, and partly sliced open to study internal structures. The preparations were extensively photographed using the microscope and camera described above. In one species focus stacking was used to obtain pictures with greater depth of field (Fig. 24), in the other dissected species the photographs served as a template to prepare drawings. Radulae were obtained by maceration of the buccal mass in 5% KOH at 60[degrees]C until the soft tissue appeared dissolved, after which the radula was rinsed with distilled water. Due to the long, narrow and transversely folded nature of these minute ribbons, most attempts to mount the radula on a SEM stub yielded unsatisfactory results.

After the presence of a deep-set palatal fold was observed in many but not in all shells (see below), special attention was paid to the presence/absence of this structure, which can be easily seen in fresh, translucent shells, or after moistening the shell surface. For those species where the available shells were too worn to ascertain the presence of this structure externally (as well as in A. acuminata), a single intact adult shell was studied using a micro CT scanner (SkyScan 1172 X-ray Microtomograph, Kontich, Belgium). The morphology of the internal barriers was examined in more detail in shell fragments of three dissected species by SEM. We only scored presence/absence of the palatal fold for each species, and did not attempt to address (potentially species-specific) variability in the expression of the structure at this stage.

RESULTS

Based on careful comparison of the habitus of the available shells which conform to the description of the genus Avakubia (e.g. Pilsbry 1919; Thiele 1933), we hypothesized the existence of at least nine morphospecies. In the available shell material we found three (sets of) characters that were previously not or incompletely addressed in the descriptions of Avakubia: (1) Cryptic barriers: most shells were found to possess a deep-set fold on the palatal wall, which appears as a white line on the body whorl of fresh (translucent) or moistened shells, but may not be observed externally in worn shells. At least some shells possessing such a palatal fold were also found to possess a short lamella (tooth) on the columella of the body whorl (Fig. 5). These two structures are not discernable in the aperture in frontal view (or even when the shell is held obliquely, apart from one noticeable exception, Fig. 19F). However, in a number of shells the palatal fold (and the columellar lamella) were found to be genuinely absent. (2) Umbilical development: most specimens possess a narrow, crevice-like umbilicus, but in some shells the umbilicus is completely closed. (3) Protoconch: the apical whorls of most shells regularly increase in diameter with growth, but in some shells coiling of the protoconch is conspicuously irregular.

[FIGURE 2 OMITTED]

The three less commonly occurring character states (absent palatal fold, closed umbilicus, irregular coiled apical whorls) were found combined in specimens from Ghana and Liberia, and we concluded that these belong to a separate genus, described below. Additional shell characters, like details of the protoconch sculpture, support this conclusion, as did preliminary anatomical observations. A detailed study of the nine available adult shells attributable to the new genus prompted the recognition of four new species. Because of the irregularly coiled protoconch in the new genus, the width of the protoconch whorls, as well as the apical angle and spire angle could not be measured in the same way as in Avakubia. These specimens were therefore analysed separately from the remaining true Avakubia material, qualitatively rather than quantitatively because of the small number of available shells.

Of the nine initially recognised morphospecies, seven were assigned to true Avakubia and two to the new genus. More detailed study suggested the existence of at least four additional species, two of each genus.

Table 1 summarizes the measurements taken from adult true Avakubia shells. In a PCA involving 87 adult Avakubia shells, the first two principal components describe most (86%) of the variation in the data. Loadings of the characters on the first three principal component axes are given in Table 2. The PC1*PC2 plot produced fairly distinct groups (Fig. 2). PC1 largely relates to size (H, D, AH, AW, BWH), whilst PC2 relates to the apical parameters (AA, SA, DW1, DW2). Rib distance (RD) constitutes an important contribution to both PC1 and PC2. Three morphospecies are obviously distinctive in size, shape and sculpture (later identified as A. acuminata, A. semenguei and A. ortizdezarateorum, see below). The remaining material is more similar in shell morphology, but all morphospecies represented by four or more individuals form well separated groups. A MANOVA indicates significant differences among most morphospecies that were recognised on the basis of PCA (Wilks' Lambda = 3.0*10e-6, df 448.8, P<<0.001), which statistically may not be a robust conclusion, since the distribution of the data appears not to be multivariately normal.

Material from the eastern DRC and Uganda formed a single cluster in the first two principal components ordination plot (Fig. 2), differing highly significantly (all Hotelling's pairwise comparisons P<0.001) from other tentative morphospecies represented by four or more measured specimens. The DRC specimens did not differ from the Ugandan material in a pairwise comparison (Hotelling's [t.sup.2]=57.825, F=2.0652, P>0.2). These shells resemble the available descriptions and illustrations of the holotype shell of A. avakubiensis (showing only characters measureable in frontal view), and were therefore classified with this species, the type locality of which is also geographically closest. A single, somewhat worn adult shell (Fig. 9K) from a central Gabonese locality (Reserve de la Lope) was placed within the A. avakubiensis cluster in PCA. However, in view of subtle differences in shell characters (using also one juvenile shell and two shell fragments from this area) and for biogeographical reasons (distance to nearest locality of A. avakubiensis being 1750 km), the inclusion in A. avakubiensis seemed insecure. Fontaine et al. (2007) tentatively considered this a new species. For the time being we classify this material as A. cf. avakubiensis.

[FIGURE 3 OMITTED]

Material from Southwest Cameroon that in an earlier study (de Winter & Gittenberger 1998) had been addressed to as Gulella (Avakubia) cf. avakubiensis, formed a well separated group in the PCA ordination plot from true avakubiensis (Fig. 2), and the two morphospecies species differed highly significantly in a pairwise Hotelling's test (P<<0.001). Three specimens from Ghana were initially classified with this Cameroon material, but formed not clearly part of the Cameroon cluster in the PCA plot and proved significantly different in a in a pairwise Hotelling's test (P<0.01), in spite of the small sample size. The Ghanaian and Cameroonian specimens are described below as two distinct species (A. occidentalis and A. fruticicola, respectively), also on the basis of non-biometric characters.

Two specimens from western Gabon, which had been provisionally assigned to a morphospecies described below as A. fruticicola, were placed close to the cluster of this species in PCA (Fig. 2). Still, on account of the different shell shape and size, combined with noticeable differences in protoconch sculpture, the Gabonese material is considered a distinct species, A. crystallum.

A number of Southwest Cameroonian shells superficially resemble A. acuminata in shape, but are consistently smaller-sized, and were therefore tentatively recognised as a separate morphospecies. This was confirmed by their separation in PCA (Fig. 2), and in pairwise Hotelling's tests, in which the material differed highly significantly from all other morphospecies represented by more than four available specimens and just significantly (P<0.05) from the others. This Cameroonian material is described below as A. subacuminata.

The material from Bioko I. (Equatorial Guinea) that had been attributed to A. avakubiensis by Ortiz de Zarate Lopez and Ortiz de Zarate Rocandio (1956), clearly embraces two rather different species. The distinct nature of the shells from the high altitude sites was already acknowledged by these authors, but they refrained from formally naming the taxon. This species is described below as A. ortizdezarateorum, and can be easily distinguished from any other Avakubia species by its shell sculpture and arrangement of the apertural barriers, but also conchometrically (Fig. 2). Specimens of the second species from lower elevations superficially resemble A. subacuminata, A. fruticicola, A. avakubiensis, A. occidentalis, and A. crystallum, but can be distinguished from all these taxa by a combination of shell measurements and appear as a separate grouping in PCA (Fig. 2), which is (highly) significantly different from the former three species in pairwise Hotelling's tests, in spite of the small number of available shells. This species is described below as A. biokoensis.

TAXONOMY

Family Streptaxidae Gray, 1860

Genus Avakubia Pilsbry, 1919

Etymology: Pilsbry's name refers to the village of Avakubi in the DRC, where the type was found. Gender feminine.

Type species: Gulella (Avakubia) avakubiensis Pilsbry, 1919, by orig. des.

Description: Shell small, with 5-7 regularly coiled whorls, adult height 3.0-5.8 mm, ovate or elongate-ovate, diameter of the penultimate whorl always exceeds that of the body whorl. Apex rounded to strongly acuminate. Coiling tightness varies substantially between species (W:lnH=3.1-5.0). Body whorl height takes up 38-56% of H, varying substantially between species. Peristome height 29-40% of H. Peristome width 44-62% of D. Aperture roundish or heart-shaped with a palatal tooth or swelling, which may be inconspicuous or virtually absent, and a protruding angular tooth that continues as an inrunning lamella for nearly a whorl. Body whorl with a deep-set palatal fold, which is generally not visible in the aperture, but appears in translucent specimens as a short white line, without a corresponding external depression. Columella with a tooth or lamella, which is externally (usually) not discernable. Umbilicus narrow, but always open. Umbilicus of juvenile specimens open and rounded, decreasing in diameter with increasing shell height. Aperture of juvenile shells edentate. Protoconch with 2-2 1/2 whorls, sculptured by ca 9-16 spiral cords of roundish or rectangular particles on the second whorl; some species have fine spiral lines in between major ones. Transition of protoconch to teleoconch marked by a rather abrupt change in sculpture. Teleoconch with strong, more or less curved, axial ribs that run from suture to suture, the interstices with fine spiral lines that do not seem to cross the axial ribs. Teleoconch spirals are not a continuation of the spiral cords on the protoconch, being more close-set, more irregular and structurally different (solid, not made up of particles).

Anatomy (Figs 6, 15, 24; based on dissections of few specimens (singletons, except for A. acuminata) of three different species, supplemented with information from unpublished drawings of a dissected specimen of A. avakubiensis kindly supplied by B. Rowson (NMW)): Salivary gland single. Penis more or less elongate, the basal portion widest. Internal penial wall distally without obvious pilasters in some species (present in A. avakubiensis, not studied in A. fruticicola), which exhibit instead irregularly shaped, larger (A. subacuminata) or smaller (A. acuminata), irregularly-shaped tissue pads. The convolute vas deferens widens more or less abruptly into a wider, rather muscular and shining terminal portion (epiphallus?). This terminal portion bends across the upper penis, and enters the penis somewhat laterally, cutting off a short apical caecum. The long penis retractor muscle originates from the columellar muscle and inserts on and/ or laterally of the penial apex, extending under the terminal portion of the vas deferens close to its entrance. Penis of most species with a lateral diverticulum (rather indistinct or absent in A. fruticicola), which appears to consists of a fleshy structure within the penial envelope. In the penis of three species (not studied in A. fruticicola) no spines or denticles were observed. In the lower penis of a specimen of A. acuminata, an elongate spindle-shaped spermatophore-like structure was encountered. Female genital tract with a short but distinct vagina, followed by a narrow free oviduct. In two specimens of A. acuminata, the oviduct is inflated into a pouch-like uterus, containing a single shelled embryo, so at least this species is ovoviviparous. Bursa copulatrix (gametolytic gland) with a long narrow duct and an ovoid or round bursal sac, which reaches the albumen gland. Hermaphrodite duct with a long, convolute tube-like diverticulum (talon). Radula ribbon very long relative to its width; after maceration the radula ribbon appears transversely folded in two portions of unequal length. Radula typical carnivorous, with a small number (<20 teeth in half a row) of elongate, sharply pointed, curved lateral and marginal teeth. Rachis present in A. acuminata, noticeably smaller than other teeth, not observed in other species.

Species included: In addition to the type species, A. acuminata (Thiele, 1933); A. biokoensis de Winter & Vastenhout, sp. n.; A. crystallum de Winter, sp. n.; A. fruticicola de Winter & Vastenhout, sp. n.; A. occidentalis de Winter, sp. n.; A. ortizdezarateorum de Winter & Vastenhout, sp. n.; A. semenguei de Winter & Vastenhout, sp. n.; A. subacuminata de Winter & Vastenhout, sp. n.

Distribution (Fig. 3): Cameroon, DRC, Equatorial Guinea (Bioko I.), Gabon, Ghana, Uganda.

Avakubia acuminata (Thiele, 1933), comb. n.

Figs 4, 5A-F, 6, 7, 10A-D

Gulella (Avakubia) acuminata: Thiele 1933: 316, fig. 61; de Winter & Gittenberger 1998: 239.

Diagnosis: Differs from other Avakubia species by the comparatively large (>5 mm) shell with tapering spire and strongly acuminate apex.

Description:

Shell (Figs 4, 5A-F, 10A-D, Table 1): Large for the genus (mean H 5.4 mm), elongate (H:D 1.88-2.1, median 1.97, in holotype 2.01), biconical, spire tapering. Coiling tightness 3.7-4.1, median 3.9, in holotype 4.0. Whorls moderately convex. Apex strongly acuminate. Protoconch comparatively high-spired, consisting of 21/4-2.5 whorls. Protoconch sculpture (Figs 10A-D) consists of comparatively regularly spaced spiral cords, 10-12 on second whorl, each 6.6-8.5 gm wide. Cords composed of series of 13-22 [micro]m long, elongate-rounded particles, that are individually just separated. Spiral sculpture starts ca 1/4 whorl from nucleus. Teleoconch sculpture consists of slightly oblique, prosocline axial ribs, 6.4-9.2 ribs/mm on penultimate whorl, median 8 ribs/mm, in holotype 7.8 ribs/mm. Interstices with fine, solid, more or less irregular spiral lines. Body whorl proportionally small, BWH 41-47% of H, median 44%, in holotype 42%. Peristome complete in most specimens; some otherwise fully developed specimens with incompletely developed parietal-angular margin are probably subadult. Peristome somewhat higher than wide, PH:PW 1.08-1.24, median 1.18, in holotype 1.19. PH 29-34% of H, median 33[degrees]%, in holotype 31%. PW 49-60% of D, median 55%, in holotype 52%. Apertural lip expanded and flaring, not strongly incrassate. Two apertural barriers visible in frontal view: a more or less pointed, tooth-like, thickening on mid-palatal wall and a conspicuous, somewhat projecting angular tooth that extends inwards as a deeply entering lamella. Internal wall of body whorl with a deep-set palatal fold (Fig. 5), not visible in the aperture, but discernable in translucent specimens as short pale stripe (Figs 4D, E). Short, little conspicuous lamella present on columella (Fig. 5), but not visible in aperture. Umbilicus open but rather narrow.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

Body colour: Live animal cream-whitish, without reddish pigment.

Anatomy (Fig. 6; five specimens dissected, including two with fully grown shells but still poorly developed genitalia): Atrium mostly longer than wide, thin-walled. Penis more or less elongate, with a short apical caecum as well as a more conspicuous lateral diverticulum. In some (juvenile or contracted?) specimens diverticulum appears subapically, nearby apical caecum, giving penis a bifid appearance. Vas deferens in some specimens coiled around vagina. Vas deferens abruptly widens close to upper penis into a muscular terminal portion that enters upper penis laterally, cutting off a short apical caecum. Penis retractor muscle long and twisted, originating from columella muscle and inserting on penial caecum, extending under widened terminal vas deferens. Interior of penis distally without strong pilasters, internal wall with small irregular tissue pads. No chitinous spines were found inside penis. A pale, elongate spindle-shaped spermatophorelike structure (Fig. 6E) with yellow content was encountered inside lower penis of one specimen. Bursa copulatrix arises from oviduct, cutting off short but distinct vagina, consisting of long narrow bursal duct with roundish oval sac. Free oviduct narrow, in two specimens strongly inflated to form a pouch-like uterus containing single, shelled, embryo. Hermaphrodite duct with long, tube-like, convolute talon.

Radula (Fig. 7): Ribbon very long and narrow. Row formula 16-C-16, number of rows not counted (n=2). Central tooth distinctly smaller than laterals. Distinction between laterals and marginals gradual, latter appearing more slender. Viewed from above, mesocone of lateral and marginal teeth appear as elongate, sharply pointed, curved blades; in other views, endocone becomes visible as a lateral dilatation.

Holotype (examined): CAMEROON: "Kamerun, wahrscheinlich [probably] Johann Albrechtshohe", Conradt (ZMB 72855).

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

Other material examined: CAMEROON: SudProv.: Minwo area ca 6 km NE Ebom, 15 km S Lolodorf, 3.10[degrees]N 10.73[degrees]E, 400-500 m, all collected within a single square kilometre of near-primary evergreen forest, from 1-3 m high understorey vegetation, except for three rather eroded empty shells (2 juv. and 1 ad.), viii-x.1995 and iii-iv.1996, A.J. de Winter & E.J. Semengue (16 samples containing 20 ad. & 6 juv. dry and 17 ad. in alcohol, of which 5 were dissected; RMNH).

Distribution (Fig. 8): For a long time A. acuminata was only known by the holotype shell, until the species was rediscovered near Lolodorf in Southwest Cameroon (de Winter & Gittenberger 1998). The type locality is uncertain ["Wahrscheinlich (probably) Johann Albrechtshohe" (Thiele 1933), presently Kumba, 4.63[degrees]N 9.45[degrees]E], which actually lies more than 200 km NW of Lolodorf. Although the occurrence of the species near the surmised type locality cannot be disproved, it may well be that the holotype was actually found closer to the second locality. Thiele (1933) mentioned Conradt as collector. It appears that Leopold Conradt, who collected especially insects, not only visited the surmised type locality, but also the Lolodorf area where he might have collected the type specimen while capturing, for example, stingless bees using a sweep net (as indicated in Eardley 2004).

Habitat: Found in a near-primary rainforest at 400-500 m elevation. Specimens were collected alive from 1-3 m high understorey vegetation, except for three rather eroded empty shells. The species lives syntopically with A. semenguei and A. fruticicola.

Remarks: A. acuminata is the largest species of Avakubia, and is readily recognizable by its characteristic elongate shell with tapering spire and acuminate apex. Its attribution to Avakubia is supported by a number of shell characters shared with A. avakubiensis, some of which may be synapomorphies, notably the beaded spiral sculpture on the protoconch, and the deep-set palatal lamella.

Avakubia avakubiensis (Pilsbry, 1919), comb. n.

Figs 9A-J, 10E-H

Gulella (Avakubia) avakubiensis: Pilsbry 1919: 234, fig. 102; Verdcourt 1962: 8; van Bruggen & Van Goethem 1997: 9, fig. 5; Schileyko 2000: 817, fig. 1069A; Wronski & Hausdorf 2010: 92; Rowson et al. 2011: 89, 91, 92.

not Gulella (Avakubia) avakubiensis of Degner 1934, nor of Ortiz de Zarate Lopez & Ortiz de Zarate Rocandio 1956.

Diagnosis: Shell differs from other Avakubia species by a combination of characters, like small size, subacute apex, and distant axial teleoconch ribs. Avakubia subacuminata generally has a larger, more elongate shell with a more sharply pointed apex and less convex protoconch whorls.

Description:

Shell (Figs 9A-J, 10E-H, Table 1; characters of the holotype are taken from the available illustrations of this shell (see Remarks)): Small (mean H 3.3 mm), ovate-biconical, largest width at penultimate whorl. H:D 1.57-1.84 in available specimens, median 1.72, in holotype ca 1.62. Coiling tightness holotype unknown, 4.3-4.6 in available specimens, median 4.5. Whorls rather convex, including protoconch whorls. Apex subacute. Protoconch consisting of ca 2.0 whorls. Pilsbry's (1919) description of the holotype protoconch sculpture broadly agrees with our observations. On last protoconch whorl, specimens from Kibale (Uganda), and Virunga National Park (DRC) have 14 irregularly-spaced spiral cords of strongly varying width, at most ca 9.5 gm wide but mainly (considerably) less. Spiral cords composed of rectangular particles of variable length, individually separated by a narrow cleft. Much finer lines are distinguishable between major spiral cords (Fig. 10H). Teleoconch sculpture consists of distantly spaced, curved axial ribs, 7.2-9.4 ribs/mm on penultimate whorl, median 8.3, with fine spirals in interstices. Body whorl height generally less than half of shell height, BWH 45-53% of H in available specimens, median 47%, in holotype 49[degrees]%. Peristome complete, mostly somewhat higher than wide, PH: PW 0.96-1.16 in available specimens, median 1.11, in holotype 1.05. PH 31-37% of H in available specimens, median 34%, in holotype 35[degrees]%. PW 50-60% of D in available specimens, median 53%, in holotype 55%. Apertural lip expanded and flaring, slightly reflected and not strongly incrassate. Two barriers visible in aperture: a weak, sometimes almost wanting, tooth-like thickening on mid-palatal wall and a projecting angular tooth that extends inwards as deeply entering lamella. Internal wall of body whorl with deep-set palatal fold, a short pale stripe is externally visible in translucent specimens. Presence of columella fold not discernible in aperture. Umbilicus narrow but open, widest in comparatively low-spired shells (e.g. Fig. 9J).

Body colour: Not recorded.

Anatomy (a specimen from Uganda was dissected by B. Rowson, who kindly allowed us to study his unpublished drawings): Vas deferens enters penis subapically. Penis with distinct lateral diverticulum and short apical caecum, on which the penial retractor muscle is attached. Overall penial morphology similar to A. acuminata (Fig. 6), but penis seems less elongate. Interior of penis with two strong and one minor pilasters, without any hooks or spines.

Holotype: DRC: Ituri, Avakubi, ca 1.318[degrees]N 27.544[degrees]E, J. Bequaert (shell could not be traced in AMNH, Christine Johnson, pers. comm., Dec. 2011). A photograph of the holotype shell in frontal view is available on http://research.amnh.org/iz/types_db/details.php?specimen_id=9951.

[FIGURE 9 OMITTED]

[FIGURE 10 OMITTED]

[FIGURE 11 OMITTED]

Other material examined: DRC: various sites within Virunga National Park [formerly Parc National d'Albert (PNA)]: 2 ad. dry shells, Abyalose, affl. Djuma, PNA, sta. A511, 800 m, 12.vi.1953, G.F. de Witte (RBINS); 2 ad., 1 juv. dry shells, Kabalwa, affl. dr. Talya, PNA, sta. A476, 1130 m, 21.v.1953, P. Vanschuytbroeck & J. Kekenbosch (RBINS); 1 ad. dry shell, Tungula, PNA, sta. A1223, 16.xii.1959, H. Synave (RBINS); 2 ad. in alcohol, Makano-Kisisile River, PNA, sta. B432, 1150 m, 27.v.1957, G.F.de Witte (RBINS); 1 ad. dry shell, PNA, sta. A877, no further data (RBINS). UGANDA: 5 ad., 2 juv. dry shells, Bushenyi, Kasyoha-Kitumi Central Forest Reserve, Kamuzuku, ca. 0[degrees]15'S 30[degrees]09'E, 1250 m, 11-12.iv.2006, T. Wronski (ZMH 52796, 52819, 53543, 53478); 1 ad., 1 juv. dry shell, Kamwenge, Kibale Forest National Park, Fort Portal towards Ibanda at bridge crossing Dura River, 0[degrees]27'26"N 30[degrees]22'51"E, 1390 m, 13.iv.2006, T. Wronski (ZMH 52709); 1 ad., 1 juv. dry shell, Kibale Forest National Park, Kanyanchu, Elephant wallow, 0[degrees]26'25"N 30[degrees]23'42"E, 1250 m, 14.iv.2006, T. Wronski (ZMH 52637); 1 dry shell, Kibale Forest National Park, Kanyanchu, 0[degrees]26'13"N 30[degrees]23'42"E, 1230 m, 14.iv.2006, T. Wronski (ZMH 52744); 1 ad. dry shell, Masindi, Budongo Central, Forest Reserve: Masindi-Butiaba road between Karongo and Busingiro, 1[degrees]42'26"N 31[degrees]28'57"E, 1080 m, 17.iv.2006, T. Wronski (ZMH 52425); 1 juv. dry shell, Mpigi, Mpanga Central Forest Reserve, Kafumo, 0[degrees]13'15"N 32[degrees]17'03"E, 1190 m, 24.iii.2006, T. Wronski (ZMH 53293); 1 ad. dry shell, Bundibugyo District, Bwamba County, Semuliki National Park, ca 0.82[degrees]N 30.16[degrees]E, 720 m, 16.vii.1996, P. Tattersfield & J.A. Allen (NMW.Z.1997.009); 1 ad. dry shell, 1 ad. in alcohol, Malabigambo Forest, ca 0[degrees]57'N 13[degrees]38'E, 1150 m, 4.ii.2007, P. Tattersfield & B. Rowson (PT).

Distribution (Fig. 11): Specimens attributed here to A. avakubiensis originate from a large area extending from Avakubi in the eastern DRC to Kampala, Uganda, a linear distance of ca 500 km. This species has the easternmost distribution of the genus and by far the largest known range. Material from the north-western DRC (Bozene, Gemena) attributed by van Bruggen and Van Goethem (1997) to this species would, if correct, increase the range considerably. Unfortunately these specimens were not available. Material from central Gabon is attributed to A. avakubiensis with doubt (see Remarks).

Habitat: The species appears to have been collected in leaf litter on the forest floor in mid-altitude moist evergreen forest between 720 and 1390 m.

Remarks: Shells from the eastern DRC and Uganda agree rather well with the original description (Pilsbry 1919) and available illustrations of the holotype of A. avakubiensis in (proportional) shell dimensions, rib distance, apical angle, and in whorl convexity.

We therefore confidently attribute these specimens to A. avakubiensis, although the holotype shell could not be studied. Still we stress the need to examine the holotype in order to confirm generic characters like an open umbilicus and the presence of a deepset palatal fold; the latter character may have been addressed by Pilsbry (1919) as "a low transverse fold... within the basal margin", but this may also refer to what we here term the columellar lamella.

Material from two nearby localities in central Gabon (Reserve de la Lope, OgooueIvindo) is considered too poor (one worn adult and one juvenile shell plus two fragments) to confidently attribute this material to A. avakubiensis. In the PCA, the only adult shell was placed well within the A. avakubiensis cluster (Fig. 2), indicating a strong resemblance in shell proportions. Fontaine et al. (2007) tentatively considered this a new species. In view of the large distance between the Gabonese records and the nearest locality of A. avakubiensis (nearly 1800 km), their view could well be correct. For the time being we classify these Gabonese specimens as A. cf. avakubiensis.

Avakubia biokoensis de Winter & Vastenhout, sp. n.

Figs 12, 18E, F

Gulella (Avakubia) avakubiensis: Ortiz de Zarate Lopez & Ortiz de Zarate Rocandio 1956: 118, fig. 22; van Bruggen & Van Goethem 1997: 9.

Etymology: The species name refers to the Bioko I., where the species is likely to be endemic.

Diagnosis: Avakubia biokoensis differs from A. subacuminata in having closer-set axial ribs on the teleoconch, a less acuminate apex, less tightly coiled whorls, and a proportionally larger peristome. A. avakubiensis can be readily distinguished from A. crystallum in having a smaller shell, more pointed apex and more widely spaced teleoconch ribs. Avakubia biokoensis differs from both A. occidentalis and A. fruticicola in having larger shell with less dense teleoconch ribs.

Description:

Shell (Figs 12, 18E, F, Table 1): Medium-sized (mean H 3.9 mm), elongate ovoid-biconical, largest width at penultimate whorl. H:D 1.68-1.91, median 1.81, in holotype 1.81. All specimens with 6 moderately convex whorls. Coiling tightness 4.33-4.47, median 4.45, in holotype 4.46. Protoconch raised but not acuminate, consisting of ca 2.0 whorls. Protoconch sculpture of holotype consists of 9-10 major spiral cords on second whorl, each 12-20 pm wide, built of poorly individualized squarish particles of very unequal length. Major cords are irregularly interspaced by thinner lines. Cords tend to be wider towards lower suture. In the RBINS paratype the spiral cords are more numerous (ca 13), and less wide, at most 8 pm. Teleoconch sculpture with relative dense, regularly spaced, curved axial ribs, about 9.8-10.8 ribs/mm on penultimate whorl, median 10.0 ribs/mm, in holotype 10.8 ribs/mm, with fine, irregular spirals in interstices. Last whorl not exceeding half the shell height, BWH 47-48% of H, in holotype 47%. Peristome complete, higher than wide; PH:PW 1.12-1.18, median 1.14, in holotype 1.13. PH 36-37% of H, median 36%, in holotype 36%. PW 53-62% of H, median 58%, in holotype 58%. Apertural lip wide and flaring, but hardly incrassate. Two apertural barriers visible in frontal view: a weak, blunt thickening on mid-palatal wall and a projecting angular tooth that extends inwards as deeply entering lamella. Internal wall body whorl with short, deep-set palatal fold, externally visible as pale stripe in holotype (Figs 12C, D). Columellar lamella externally not discernable in the available specimens. Umbilicus narrow but open.

Body colour. Dried tissue in holotype shell pale orange-red.

Anatomy: Unknown.

Holotype: EQUATORIAL GUINEA: Bioko I.: Basile Bubi, ca 3.7[degrees]N 8.8[degrees]E, ca 400 m, ix.1946, Antonio Ortiz de Zarate, ex colln Altimira (see van Bruggen (1973)) (RMNH.MOL.327295).

Paratypes (localities verbatim from label in italics): 1 ad. dry shell Basile Bubi [Rio Bireborico (=Bericorico?], ix.1946, Antonio Ortiz de Zarate (RBINS 21612); 1 ad. dry shell Basile Bubi, En Rio Borabecho, 4.iv.1954, Antonio Ortiz de Zarate (MNCN 15.05/26565); 1 ad. dry shell Basile, Bericoricoy Borabecho (orig. handwritten lable, printed museum label reads: Rios Ericorico y Borabecho, Basile), ix.1947, Adolfo Ortiz de Zarate (MNCN 15.05/26569).

Distribution (Fig. 8): Only known from a few localities near Basile. The species is likely to be endemic to Bioko I.

[FIGURE 12 OMITTED]

Habitat: Unknown except for a few notes by Ortiz de Zarate Lopez and Ortiz de Zarate Rocandio (1956: 118): lives in forest along a stream; a specimen from Bonyoma (see Remarks) was found in secondary forest. A. biokoensis is probably a lowland species (in contrast to A. ortizdezarateorum), the area around Basile lying at around 400 m.

Remarks: The apical sculpture of two specimens, the holotype and the RBINS paratype, differs in number and width of the spiral cords (studied by SEM). The sculpture of the third available specimen (studied under a stereomicroscope, 60* magnification) resembles that of the holotype, the fourth shell that of the Brussels paratype. We provisionally consider this a case of intraspecific variation.

All material of this species was originally in the collection of Adolfo Ortiz de Zarate Lopez, who exchanged Fernando Poo land snails with various professional and amateur malacologists. Only four specimens of A. biokoensis could be located for this study. Ortiz de Zarate Lopez's collection with two specimens arrived in MNCN Madrid after his death. The best preserved, evidently live-collected, shell studied by us was originally in the collection of C. Altimira, now in RMNH. Another specimen was exchanged with the late W. Adam and is now in RBINS. Ortiz de Zarate Lopez and Ortiz de Zarate Rocandio (1956) list seven specimens from Basile Bubi, but the collection dates differ from those on the labels of the material studied here. This suggests that the number of shells of A. biokoensis in the Ortiz de Zarate Lopez's collection originally has been larger, the whereabouts of missing material being unclear. In RMNH, there is a copy of an unpublished list (dated March 1958, probably compiled by A. Ortiz de Zarate Lopez) of terrestrial Mollusca from Fernando Poo sent to the "Direccion General de Provincias y Plazas Africanas", mentioning material of "G. (A.) avakuviensis" (sic) from Basile Bubi. The fate of this institute's collection appears to be unknown (Villena et al. 1997).

Ortiz de Zarate Lopez and Ortiz de Zarate Rocandio (1956) mention a single specimen from Bonyoma that is said to differ by a smaller shell, proportionally less elongate aperture, straight outer lip and a not ascending last whorl. The whereabouts of this specimen, which might constitute still another Avakubia species on Bioko, is presently unknown. Material from the Pico de Isabel listed by these authors belongs to A. ortizdezarateorum.

Avakubia crystallum de Winter, sp. n.

Figs 13, 18G, H

Gulella (Avakubia) cf. avakubiensis: de Winter 1995: 225.

Etymology: The species name is a noun in apposition and refers to the type locality (Monts de Cristal), as well as to the glassy, gem-like appearance of the fresh shell (especially with the red softparts inside), which, however, is not unique for this species.

Diagnosis: Resembles A. fruticicola, especially by its (slightly less) close-set teleoconch ribs, but this species has a smaller, less elongate shell with less rapidly expanding whorls, less sharp apical angle and spire angle, proportionally larger body whorl, and differs in protoconch sculpture. The shell of A. biokoensis is larger and more oval, with a smaller number of spiral cords on the protoconch; the shell of A. occidentalis is similarly shaped, but has a less densely ribbed teleoconch, tighter coiled whorls and different protoconch sculpture; A. crystallum resembles A. avakubiensis only superficially, differing by a larger shell with much less widely spaced ribs, as well as in details of the protoconch sculpture.

Description:

Shell (Figs 13, 18G, H, Table 1): Medium-sized (mean H 3.7 mm), ovate-biconical, largest width at penultimate whorl. H:D in holotype 1.79, in other specimen 1.79. Whorls expanding rather fast: coiling tightness in holotype 4.1, in other specimen ca 4.0. Whorls moderately convex. Apex slightly pointed. Protoconch consisting of ca 2.0 whorls, second protoconch whorl convex, contour resembling that of A. avakubiensis. Protoconch sculpture of holotype consists of 15 regularly spaced spiral cords on last protoconch whorl, each 6.2-8.5 pm wide, without noticeably thinner lines between them. Spiral cords made up of adjoining but distinct particles of variable length, but generally longer than wide. Teleoconch sculpture of rather close-set, curved, slightly oblique axial ribs, ca 10.7 ribs/mm on penultimate whorl in holotype, 11.1 ribs/mm in other specimen, with fine spirals in interstices. Last whorl takes up half the shell height or less, in holotype BWH 50% of H, in other specimen 47%. Peristome complete in holotype (not in other specimen, measurements are estimates), somewhat higher than wide, PH:PW in holotype 1.15, in other specimen 1.08. PH 37% of H in holotype, in other specimen 29%. PW 58% of D in holotype, in other specimen 49%. Apertural lip holotype expanded and flaring, slightly reflected and somewhat incrassate. Two apertural barriers visible in aperture: a weak, thickening on mid-palatal wall and a slightly projecting angular tooth that extends inwards as deeply entering lamella. Internal palatal wall of body whorl with a deep-set palatal fold (no longer visible in coated holotype, nor in other specimen which is worn). Columellar lamella not visible in aperture. Umbilicus narrow but open.

[FIGURE 13 OMITTED]

Body colour: Holotype with conspicuously pinkish red coloured soft parts (collector's observation).

Anatomy: Unknown.

Holotype: GABON: Region Estuaire: Monts de Cristal, ca 5 km N of Kinguele, 0.5[degrees]N 10.3[degrees]E, 400 m, 26.xii.1989 J.J. Wieringa, wet rocky slope in rainforest (RMNH.MOL.330185).

Other material examined: GABON: Region Ngounie: 1 ad. dry shell, Ofoubou area, ca 30 km W of Mandji, 1.75[degrees]S 10.10[degrees]E, ca 50 m, vii.1991, J. Reitsma, rainforest (RMNH.MOL.330186).

Distribution (Fig. 11): Western Gabon.

Habitat: The holotype was collected from a Begonia plant (B. letouzeyi Sosef) growing on a wet rock along a stream in undisturbed rainforest at 400 m. The other specimen, an eroded empty shell, was found in a leaf-litter sample in undisturbed lowland rainforest.

Remarks: This species is somewhat intermediate between A. fruticicola and A. biokoensis in shell size and rib sculpture. In shell shape it best resembles A. occidentalis. Still, the two western Gabonese shells appear to be recognisable by a number of characters, and we prefer to treat these specimens as a new species, also in view of the considerable (300 to 1200 km) geographic separation between the known localities of these species and those of A. crystallum. Specimens reported from Central Gabon by Fontaine et al. (2007) are clearly not conspecific with A. crystallum, and more closely resemble A. avakubiensis (as discussed there).

Avakubia fruticicola de Winter & Vastenhout, sp. n.

Figs 5H, 14, 15, 18A-D

Gulella (Avakubia) cf. avakubiensis: de Winter & Gittenberger 1998: 239.

Etymology: From Latin frutex (shrub, bush) and colere (to inhabit), in reference to the understorey-dwelling habit of this species.

Diagnosis: Avakubia fruticicola differs from other Avakubia species by the combination of its small sized shell with proportionally large body whorl, rounded apex, and close-set teleoconch ribs.

Description:

Shell (Figs 14, 18A-D, Table 1): Small (mean H 3.3 mm), ovate-biconical, largest width at penultimate whorl. H:D 1.62-1.79, median 1.68, in holotype 1.67. Whorls expanding comparatively fast, coiling tightness 4.0-4.4, median 4.2, in holotype 4.2. Whorls convex. Apex raised, but more flattened than most similarly-sized species. Protoconch consisting of ca 2 whorls. Protoconch sculpture (on second whorl) composed of ca 13 spiral cords, more or less regularly spaced, each 3.5-7.6 pm wide, without thinner lines between them. Spirals cords are made up of series of adjoining, but distinct, particles of variable length. Teleoconch sculpture with comparatively close-set, regularly spaced, curved axial ribs, 10.7-12.8 ribs/mm on penultimate whorl, median 11.3, in holotype 11.5, interstices with fine spiral lines. Body whorl proportionally large, BWH 49-55% of shell height, median 53%, in holotype 53%. Peristome complete, roundish to (mostly) somewhat higher than wide; PH: PW 0.92-1.15, median 1.11, in holotype 1.10. PH 35-39% of H, median 37%, in holotype 37%. PW 53-61% of D, median 57[degrees]%, in holotype 56%. Apertural lip expanded and flaring, slightly reflected, not strongly incrassate. Two barriers visible in aperture: a rather weak, often nearly absent, thickening on mid-palatal wall and a projecting angular tooth that extends inwards as deeply entering lamella. Internal wall of body whorl with deep-set palatal fold, externally visible as pale stripe in fresh specimens (Figs 18C, D). Columellar lamella not visible in aperture, facing palatal fold, little pronounced (Fig. 5H). Umbilicus punctiform but open.

Body colour: Live animal reddish, dried-in tissue often retains red pigments.

Anatomy (Fig. 15; one paratype dissected): Genitalia overall similar to those in A. acuminata and A. subacuminata, but smaller. Upper penis appreciably narrower and more muscular than distal portion. Lateral diverticulum of penis, if present, rather poorly developed, merely an inconspicuous dilatation at the transition of two penial portions. Internal penis not examined.

[FIGURE 14 OMITTED]

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

Holotype: CAMEROON: Sud Prov.: 14 km S Lolodorf, plot I2 (de Winter & Gittenberger 1998, sta. CAM.22a), 3.10[degrees]N 10.73[degrees]E, 470 m, 21.ix.1995, A.J. de Winter & E.J. Semenguei (RMNH.MOL.42806).

Paratypes: CAMEROON: same locality and collectors as for holotype but 460-530 m: 1 juv. dry shell, 1 ad. in alcohol, sta. CAM.010, 30.viii.1995 (RMNH.MOL.42802, RMNH.MOL.254634); 1 ad. dry shell, sta. CAM.011a, 30.viii.1995 (RMNH.MOL.42803); 1 juv. dry shell, sta. CAM.012a, 31.viii.1995 (RMNH. MOL.42804); 2 ad. dry shells, sta. CAM.018a, 19.ix.1995 (RMNH.MOL.42805); 3 ad. dry shells, sta. CAM.038,6.x.1995 (RMNH.MOL.42807); 1 ad. dry shell, sta. CAM.039a, 6.x.1995 (RMNH.MOL.42808); 1 ad., 1 juv. dry shell, sta. CAM.068a, 1.iv.1996 (RMNH.MOL.254637); 1 ad., 1 juv. dry shell, 1 juv. in alcohol, sta. CAM.075a, 10.iv.1996 (RMNH.MOL.254635; RMNH.MOL.254640); 1 ad. in alcohol, sta. CAM.076a, 9.iv.1996 (RMNH.MOL.330189); 1 ad. in alcohol, sta. CAM.077a, 10.iv.1996 (RMNH. MOL.254638); 1 ad., 1 juv. dry shell, sta. CAM.078a, 10.iv.1996 (RMNH.MOL.254641); 1 juv. dry shell, sta. CAM.081a, 11.iv.1996 (RMNH.MOL.254642).

Other material examined: CAMEROON: Sud Prov.: 1 specimen in alcohol, sta. CAM. 34a, ca 250 m SW of Ebom II, 19 km S of Lolodorf, 3.05[degrees]N 10.70[degrees]E, 400 m, 5.ix.1995 (RMNH.MOL.330325); 1 ad., 2 juv. dry shells, sta. CAM.86a, Nyangong, 30 km S of Lolodorf, 2.966667[degrees]N 10.73333[degrees]E, 650 m, swamp forest, 24.iv.1996 (RMNH.MOL.330326); 1 ad. dry shell, sta. CAM.101a, Nyangong, 2.95[degrees]N 10.73[degrees]E, 700 m, undisturbed forest on steep, N-facing slope, 9.v.1996 (RMNH.MOL.330327); 1 juv. dry shell, sta. CAM.111a, Meka'a-II, W of Nyangong, 2.966[degrees]N 10.733[degrees]E, 690 m, 18.v.1996 (RMNH.MOL.330328).

Distribution (Fig. 11): Only known from two areas in Southwest Cameroon, ca 25 km distant and differing somewhat in altitude (400-500 vs 600-700 m).

[FIGURE 15 OMITTED]

Habitat: Live specimens and empty shells were collected from the understorey vegetation up to three metres above the forest floor in little disturbed rainforest between 400 and 700 m. At the type locality A. fruticicola lives syntopically with A. semenguei and A. acuminata. In the Nyangong area A. fruticicola occurs sympatrically with A. subacuminata, but the latter species was more often found on the forest floor.

Remarks: Avakubia fruticicola is quite distinct from A. avakubiensis, to which species the material had earlier been tentatively attributed (de Winter & Gittenberger 1998). The two species differ in teleoconch rib spacing, coiling tightness, width of the apical whorls, apical angle, proportional aperture and body whorl size, and whorl convexity. A. occidentalis has a proportionally smaller aperture and body whorl, and slightly wider spaced (but still comparatively close-set) ribs. A. fruticicola resembles A. crystallum in axial ribbing, but has a smaller and less cylindrical shell with more convex whorls, a less pointed apex, and a proportionally larger body whorl. A. biokoensis differs by the larger, more cylindrical shell and proportionally smaller body whorl.
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Title Annotation:p. 605-635
Author:de Winter, A.J.; Vastenhout, N.
Publication:African Invertebrates
Article Type:Report
Geographic Code:60AFR
Date:Dec 1, 2013
Words:8592
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