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Afrorhytida kraussi oraria subsp. n.

Afrorhytida kraussi oraria subsp. n.

Figs 55F, 63, 64E, F, 65A-C

Etymology: From orarius (Latin), of the coast; referring to its association with coastal fynbos and dune strandveld habitats.

Identification (Fig. 65): For general description see Afrorhytida k. kraussi above. Shell shape and sculpture resembling A. k. kraussi, but with distinctive coloration (see below); protoconch smaller (diameter 2.5-3.0 mm) and shell thicker. Does not appear to attain as large a size as the nominotypical subspecies (diameter of largest specimens 23.1 and 28.4 respectively), but adult size evidently varies considerably in the latter.

Periostracum very thin, pale buff, not evident in most specimens; underlying shell mostly whitish with apical region frequently darker, pinkish purple to maroon; last adult whorl often with occasional, irregular, purplish or maroon-brown axial bands, particularly behind outer lip of adult. Shell also sparsely pock-marked with small, dark flecks, these often associated with small growth imperfections; interior of aperture buffish in fresh specimens, the darker subterminal band, if present, visible through shell.

[FIGURE 65 OMITTED]

Dimensions: Holotype, diameter 22.3 mm, height 13.3 mm; largest specimen (NMSA W3297), diameter 23.1 mm, height 13.3 mm; H:D of adults 0.56-0.64 (N=12).

Living animal (data available for only one specimen) (Fig. 55F): Head-foot coloration similar to that of typical A. k. kraussi, but somewhat darker maroon-brown, very dark dorsally; pedal margin tinged with orange; mantle edge similarly maroon-brown; lung wall with some irregular dark pigmentation, mostly tracking underlying blood vessels.

Radula (Figs 64E-F): As in A. k. kraussi.

Distal genitalia: All live-taken material immature.

Holotype (Figs 65A-C): SOUTH AFRICA: W. Cape: De Hoop Nat. Res. (34.450[degrees]S:20.383[degrees]E), 60 m, W. Sirgel, don. i/1999 (NMSA V6780/T2361).

Paratypes: SOUTH AFRICA: W. Cape: De Hoop Nat. Res. (34.47512[degrees]S:20.51969[degrees]E), coastal dune scrub, in leaf-litter, A. Moussalli & D. Stuart-Fox, 24/ii/2005 (NMSA W3292/T2363, 1juvenile specimen; W3297/ T2362, 8 adult specimens, 2 juveniles; ELM D15857, 1 specimen); De Hoop Nat. Res., around Koppie Alleen (34.4667[degrees]S:20.5167[degrees]E), ground-dwelling in strandveld, A. Wood, 22/viii/1994 (NMSA W5776/ T2364, 2 specimens).

Distribution (Fig. 63): A narrow-range endemic; known only from the De Hoop Nature Reserve, W. Cape, South Africa, at altitudes of <100 m.

Habitat: Recorded only from De Hoop limestone fynbos and Overberg dune strandveld (cf. Mucina & Rutherford 2006); in sandy soil beneath forbs, shrubs and bushes.

Notes: The considerable degree to which Afrorhytida k. oraria differs in shell characters from the nominotypical subspecies would traditionally result in it being considered a distinct species. However, in the analysis of molecular data undertaken by Moussalli et al. (2009), this De Hoop material clustered within the broader assemblage of material considered to represent the A. kraussi complex. Its radula too is indistinguishable from that of members of this complex. Although this assemblage exhibits considerable genetic diversity and may ultimately be shown to be an aggregate of sibling taxa, with the exception of specimens from De Hoop, we have been unable to identify any consistent spatially or genetically correlated patterns in the morphological variation evident. However, since this De Hoop material is clearly conchologically distinct, we consider it merits nomenclatural recognition as a diagnosable entity, ranked for the present as a subspecies. We are aware, however, that some of the conchological characters of this coastal lineage may relate to environmental conditions, particularly edaphic characters (calcium-rich soils) and this is a topic requiring further study.

Conservation: Afrorhytida k. oraria is evidently a taxon of restricted range, but it occurs in a surprisingly poorly sampled area and additional survey work is needed in order to obtain a clearer picture of its distribution. Although currently known only from De Hoop Nature Reserve, the coastal limestone habitat, which it evidently favours, extends considerably beyond the confines of this reserve in the broader Bredasdorp-Stilbaai area. The taxon may thus have a somewhat less restricted distribution than the available data indicate. A meaningful assessment of its threat status must await further information, but this notwithstanding, potential threats are evident, particularly habitat transformation due to the invasion of exotic Acacia species.

Afrorhytida burseyae sp. n.

Figs 10B, 54D, 55G, 66-69

Etymology: Named for Mary Bursey (now Cole), malacologist at the East London Museum who has collected much valuable land snail material and helped enormously with field logistics.

Identification: Shell very similar to that of elevated specimens of A. knysnaensis, but with a somewhat narrower umbilicus. Differs consistently from that species in having more lateral teeth and fewer marginal teeth in the radula (Table 2), and comprises a distinct genetic lineage within Afrorhytida. Evidently restricted to the region encompassing the catchments of Kei and Mbashe rivers, whereas A. knysnaensis occurs further to the west, in the catchments of the Sundays and Great Fish rivers.

[FIGURE 66 OMITTED]

Description (Fig. 66): Shell subglobose, somewhat turbiniform; comprising up to 4.5 whorls, last adult whorl descending prior to aperture, but sometimes only weakly so; base glossy, apical surface less so, but still retaining some lustre when fresh. Protoconch 4.4-5.0 mm in diameter; apical portion more or less smooth, axial riblets developing during first whorl, initially weak, but strengthening toward end of whorl; protoconch/ teleoconch junction usually poorly defined. Apical surface of teleoconch sculptured by close-set axial riblets, these becoming weaker and less well defined toward end of last adult whorl and on base; traces of weak, close-set, spiral liration between axial riblets, particularly on base; aperture subcircular to roundly-ovate; outer lip slightly thickened basally though scarcely so elsewhere (but most specimens slightly subadult and lip rather thin throughout); upper part of outer lip not flattened; umbilicus narrow, its margin rather steeply curving, partially obscured by reflected upper portion of columella lip in adults.

Fresh specimens more or less uniformly yellow-ochre to olive-green; little difference between apical and basal surfaces; occasional very slightly darker radial bands may be present.

Dimensions: Holotype, diameter 21.1 mm, height 17.5 mm; largest specimen (NMSA V6634, 'Pondoland'), diameter 26.4 mm; H:D of adults 0.74-0.87 (N=16).

Living animal (Fig. 55G): Head-foot pale apricot-orange to pale grey-brown; neck region somewhat darker brown, sometimes with a paler, dorsolateral, longitudinal stripe on each side extending backwards from optic tentacle; tentacles darker grey; sides of foot generally pale, often with a narrow orange band at pedal margin; mantle edge greyish white to apricot-orange; lung wall with limited black pigmentation.

Radula (Fig. 67): Formula 1+(12-14)+(7-9) (N=4); length up to 15.4 mm, with 60-70 V-shaped rows of teeth, 4.3-4.6 rows/mm in adult. Rachidian cusp somewhat longer than its base-plate. Inner lateral teeth (1-10) differing little in size, long and slender, more or less parallel-sided, apically acuminate with the tip sometimes slightly curved outward; outermost 3 or 4 lateral teeth increasing rapidly in size and developing stout quadrate base-plate, with relatively slender, gently curved, sharply pointed cusp; penultimate lateral is the largest. Innermost marginal tooth relatively large (approx. 0.66 length of outer lateral), second marginal retaining distinct cusp but subsequent marginals vestigial.

[FIGURE 67 OMITTED]

Distal genitalia: Epiphallus approx. 75 % length of penis; thick-walled for most of its length and frequently strongly curved; lumen wall with low, indistinct ridges between which are numerous, close-set, transverse pockets, representing openings of diverticulae in epiphallus wall (Fig. 54D); these concentrated in middle two-thirds corresponding with spinose mid-piece of spermatophore; sparse toward vas deferens and junction with penis.

[FIGURE 68 OMITTED]

Spermatophore (Fig. 68): Well preserved allospermatophores have been found in the female tract of two specimens collected in early March, one per specimen. Spermatophore white to pale pink, U-shaped and of firm texture, evidently variable in size (about 6.5 mm and 10.5 mm in total length); comprising three distinct regions, a bluntly acuminate head, a broader, U-shaped mid-piece and a short, recurved tail. Inner surface of bend with a deep, longitudinal depression or groove, but otherwise spermatophore lacking strong longitudinal grooves/ridges; outer surface of mid-piece bearing numerous, small, close-set, forwardly directed, spine-like projections pressed flat against its surface; spines compound (finely branched apically); tail and head piece with few spines. No obvious vent present in the tail region, but spermatophore contents visible in inner groove of mid-piece in one specimen.

Spermatophores situated in upper part of vagina, in one specimen the head extended into base of free oviduct, in the other it extended into base of bursa copulatrix duct. Anterior half of mid-piece level with origin of bursa copulatrix duct and end of free oviduct, tail extending backward into lower, longitudinally ridged portion of vagina.

Surprisingly the spines on the mid-piece are directed toward the head region, an orientation which might impede rather than facilitate the passage of the spermatophore within the vagina, suggesting that it is deposited in this position by the penis of the partner during copulation. Even so, this orientation would seem to hinder its release from the epiphallus into the penis. The spines, however, appear less rigid than in other species suggesting a degree of flexibility. They may serve an anchoring function, holding the spermatophore in place once deposited.

Holotype (Figs 66A-C): SOUTH AFRICA: E. Cape: Wedgeley farm, Kei R. valley, NNE of Stutterheim, (32.28986[degrees]S:27.54674[degrees]E), 845 m, grassy bushveld, crawling at night on grass and stones beside farmhouse after rain, D. Herbert & L. Davis, 4/iii/2007 (NMSA W5228/T2257).

Paratypes: SOUTH AFRICA: E. Cape: same data as holotype (ELM D15855, 1 specimen; BMNH 20100126, 1 specimen; NMSA W5229/T2258, 3 specimens; NMSA W5230/T2259, 1 specimen; NMSA W5231/T2260, 1 specimen); Engcobo (31.66[degrees]S:28.00[degrees]E), ca 975 m (SAMC A11289, 1 specimen); Cathcart (32.29241[degrees]S: 27.13567[degrees]E), 1210 m, montane grassland/bushveld, small juvenile on grass blade, A. Moussalli, D. StuartFox & M. Bursey, 30/xi/2005 (NMSA W4844/T2261, 1 specimen, juvenile); Sterkstroom, Koos Ras Nat. Res. (31.54935[degrees]S:26.57283[degrees]E), 1440 m, rocky outcrop with trees and shrubs, buried under grass clump, Herbert, Davis, Cole & Fearon, 09-005, 29/iii/2009 (NMSA W6712/T2489, 2 specimens, subadult); Mbashe River valley nr N2 bridge (31.92461 [degrees]S:28.45113[degrees]E), 465 m, riverine thicket, in leaf-litter and under fallen aloes, A. Moussalli & D. Stuart-Fox, 23/xi/2005 (NMSA W5372/T2349, 3 specimens); Kei Pass (32.49364[degrees]S: 27.99175[degrees]E), 270 m, valley thicket, under rocks, A. Moussalli & D. Stuart-Fox, 23/xi/2005 (NMSA W5484/ T2347, 1 specimen); Gonubie R., Slippery Drift (32.80055[degrees]S:27.85583[degrees]E), ca 200 m, Jansen, 28/xii/2002 (ELM D13766, 1 specimen); East London area, 20 km inland, nr Nahoon Dam, Elizweni resort (32.915297[degrees]S: 27.818867[degrees]E), 140 m, thicket on north facing slope above Nahoon R., in leaf-litter, M. Bursey, 18/i/2007 (NMSA W5252/T2346, 2 specimens); ditto, Elizweni resort, on west bank of Nahoon R., M. Bursey, 18/iv/ 2006 (ELM D14971, 5 specimens); Berlin area, Mncotsho, Buffalo R. valley (32.917[degrees]S:27.583[degrees]E), ca 360 m, grassland with scattered bushes near beacon, M. Cole & C. Vernon, 06/xi/2007 (NMSA W6004/T2348, 3 specimens).

Other material examined: SOUTH AFRICA: E. Cape: Bailey, ca 1300 m, Miss Hickey (NMSA B0097); Ugie, ca 1300 m, Miss L. Britten, i/1923 (NMSA E7906); 'Pondoland', Mrs A. Filmer (NMSA V6842, V6634).

Distribution (Fig. 69): Endemic to E. Cape; recorded primarily from inland localities in the Great Kei River catchment and eastwards to the Mbashe and Mzimvubu catchments, but recorded also from smaller coastal drainage systems in the East London area (Buffalo, Nahoon and Gonubie rivers); occurs at altitudes of 140-1440 m.

Habitat: Evidently favours somewhat open habitats rather than forest; recorded from a range of vegetation types including grassy bushveld, montane shrubland and various types of thicket; hiding under fallen aloes and in grass clumps between rocks.

[FIGURE 69 OMITTED]

Notes: This species was initially thought to represent Natalina eumacta (Melvill & Ponsonby, 1892). However, examination of the holotype of that species BMNH (1905.1.26.2, Figs 24A-C) shows it to be considerably larger (diameter 30.3 mm) than any specimens of the present species. In addition it is not as globose, has a larger protoconch and lacks any thickening of the aperture lip. We consider that N. eumacta represents the eastern coastal subspecies of Natalina cafra (see above).

The shell of Afrorhytida burseyae closely resembles that of elevated specimens of A. knysnaensis such as occur in the Greater Fish River Conservancy, and indeed it cannot be reliably distinguished from such specimens on shell features alone. Although few specimens have been observed alive, the head-foot colour of A. burseyae also resembles that of some specimens of the variably coloured A. knysnaensis and, given this variability in the latter species, body colour also seems unlikely to prove useful for species discrimination. However, the radula of A. burseyae differs markedly and consistently from that of A. knysnaensis in having many fewer marginal teeth and in the penultimate rather than the outmost lateral being largest. In these features it resembles A. trimeni from which it differs conchologically in having a considerably more globose, yellowish green rather than brown shell, with weaker axial sculpture and a much narrower umbilicus. Molecular data confirms that A. burseyae constitutes a distinct lineage within the Afrorhytida radiation, though its relationships to the other species are not resolved (Moussalli et al. 2009). Its radula morphology suggests that it is perhaps most closely related to A. trimeni, whereas its epiphallus morphology is closer to that of A. kraussi (Fig. 54).

Conservation: Although few specimens of Afrorhytida burseyae are available, it occurs in a very poorly sampled area and it may not be scarce where conditions are favourable. Its known extent of occurrence is considerable (approx. 15,000 km2) and given that it favours open habitats, its area of occupancy is not likely to be particularly limited or fragmented. Thus despite being a newly discovered taxon, it seems unlikely that A. burseyae is threatened at present. In the long term, however, the continued transformation of natural habitats, associated with agricultural expansion, represents a potential threat, particularly so since the distribution of A. burseyae currently includes very few, if any, formally conserved areas.

Afrorhytida trimeni (Melvill & Ponsonby, 1892)

Figs 4B, 54C, 55H, 70-72

Helix (Aerope) trimeni: Melvill & Ponsonby 1892: 237, pl. 13, fig. 1. Type loc.: given as 'S. Africa', but label states 'Cape Colony' [Trimen].

Natalina tremeni [sic]: Pilsbry 1893 in 1892-93: 135.

Natalina trimeni: Pace 1895: 232; Melvill & Ponsonby 1898: 170; Sturany 1898: 31; Connolly 1912: 97; 1939: 114; Barnard 1951: 142, pl. xxi, fig. 7.

Rhytida (Afrorhytida) trimeni: Mollendorff 1903: 62, pl. 11, fig. 3.

Natalina arguta Melvill & Ponsonby, 1907: 98, pl. 6, fig. 8; Connolly 1912: 90; 1939: 115; Watson 1934: 156, pl. 19, fig. 10 [radula]. Type loc.: East London, E. Cape [Burnup]. Syn. n.

Etymology: Named for Roland Trimen (1840-1916), an entomologist and curator at the South African Museum (1872-95), who sent the original specimens to Melvill and Ponsonby.

Identification: The shell of Afrorhytida trimeni is characterised by its brownish rather than greenish colour and the fact that the axial sculpture remains distinct even on the last adult whorl. A. kraussi kraussi has a similarly brown shell, but the whorls are less deep and the upper part of its outer lip is usually distinctly flattened; its radula also has more marginal teeth and lacks lateral flanges on the inner laterals. In terms of its radula A. trimeni is most similar to A. burseyae in that there are relatively few marginals (<10), but in the latter the innermost laterals lack lateral flanges and distinctly uncinate tips. Its shell is also considerably more globose and of a more yellowish green hue. A. knysnaensis is likewise generally more globose (except those from the north-west of its range) and more yellowish, and its radula has many more marginal teeth of intermediate size.

Description (Fig. 70): Shell globose-lenticular, spire height generally low but rather variable; comprising up to 4.75 whorls, last adult whorl descending slightly prior to aperture; apical surface lustreless, base more glossy. Protoconch diameter 3.5-4.1 mm, initially somewhat smooth, but with distinct axial riblets developing along adapical suture during first whorl, these extending to abapical suture on second whorl (Fig. 4B); protoconch/teleoconch junction usually poorly defined. Apical surface of teleoconch sculptured throughout by close-set axial riblets, these not becoming noticeably weaker on last adult whorl; riblets weaker below periphery and on base, but becoming stronger again around and into umbilicus; base with traces of weak, close-set, spiral lirae; aperture roundly-ovate; outer lip weakly, but distinctly thickened in adult, white; upper part of outer lip not or only minimally flattened; umbilicus deep and relatively wide, scarcely, if at all obscured by upper part of columella lip.

[FIGURE 70 OMITTED]

Fresh specimens more or less uniformly mid brown; little difference between apical and basal surfaces except that the former is dull and the latter glossy; some specimens with faint traces of slightly darker radial banding. Brown colour fading after death and becoming more yellowish brown; old specimens frequently yellow-ochre.

Dimensions: Largest specimen (NMSA W5254, Hamburg), diameter 25.5 mm; H:D of adults 0.56-0.70 (N=18).

[FIGURE 71 OMITTED]

Living animal (Fig. 55H): Information available from photographs of only two specimens. Head-foot grey-brown dorsally, with a paler longitudinal stripe extending backward from each optic tentacle, bordered ventrally by a conspicuous dark, grey-black line, boldest beneath shell; paler dorsal areas slightly tinged with apricot; sides of foot pale greyish white with darker skin grooves, slightly darker just above pedal margin; pedal margin itself whitish, slightly tinged with apricot; tentacles darker grey or greybrown; mantle edge pale greyish white; lung wall often extensively marked with fine, anastomosing black blotches, not obviously following pattern of lung venation.

Radula (Fig. 71): Formula 1+(13-14)+(6-9) (N=4); length up to 19.5 mm, with 56-76, broadly V-shaped, transverse rows of teeth, 3.9-4.4 rows/mm in adult. Rachidian about two-thirds length of innermost lateral; cusp broadly acuminate, slightly longer than its base-plate. Inner lateral teeth (1-10), relatively short and broad, increasing only slightly in size, their cusps with a lateral flange on outer margin and a bluntly rounded apex bearing a small but distinct uncinate tip (Fig. 71C); outermost 3 or 4 lateral teeth increasing rapidly in size and developing a stout quadrate base-plate, with a strong, gently curved, sharply pointed cusp; penultimate lateral is the largest. Innermost marginal considerably smaller than outer lateral, with a much reduced base-plate, but retaining a distinct cusp; remaining laterals progressively smaller, the fourth and subsequent vestigial.

Distal genitalia: See generic description. Wall of penis lumen coarsely papillate; epiphallus approx. 0.75 length of penis; its internal structure (Fig. 54C) similar to that of A. knysnaensis in possessing longitudinal ridges with digit-like tips, except that there are only four such ridges additional to the pair of folds running along the inner wall, and the ridges are longer than in A. knysnaensis, extending forwards for approx. 0.75 of epiphallus length from its junction with vas deferens. Anterior to this the lumen wall is smoother, but bears indistinct longitudinal rows of pits running forward from the intervals between the swollen tips of the longitudinal ridges.

Spermatophore: No spermatophores have been found, but the internal morphology of the epiphallus suggests that the mid region and tail will be largely smooth, perhaps only with weak longitudinal furrows, but the anterior portion will bear approx. five rows of small spines on its outer, convex surface.

Type material: Lectotype of Helix (Aerope) trimeni Melvill & Ponsonby, 1892 (designated Connolly 1912: 97) (= figured syntype) in BMNH (1911.8.8.3), diameter 23.8 mm (24.2 mm fide Connolly 1939) (Figs 70A-C). Three paralectotypes in NMW 1955.158.736. Holotype of Natalina arguta Melvill & Ponsonby, 1907 in BMNH (1911.8.8.6), diameter 20.5 mm (Figs 70D-F); one paratype in NMSA (1495/T593).

Additional material examined (all NMSA unless otherwise indicated): SOUTH AFRICA: E. Cape: Grahamstown, C.J. Swierstra, vi/1925 (V5278); ditto, ex Farquhar Coll'n (BMNH 1937.12.30.1345); ditto, bottom of Fernkloof, 475 m, under stones, i/1912 (E7908); Kap River Nat. Res. (33.48541[degrees]S: 27.08474[degrees]E), 65 m, indigenous forest, in leaf-litter, A. Moussalli, D. Stuart-Fox & M. Bursey, 9/xii/2005 (W4206); Port Alfred area, nr Kleinemonde, Tharfield farm. Miss E. L Barber (W5986); Begha R., Peddie District, J. Hewitt, xii/1935 (V6849); Hamburg, Keiskamma R. mouth (33.27555[degrees]S: 27.48639[degrees]E), 3 m, riverine forest on east bank near river mouth, in leaf-litter, M. Bursey, 14/ii/2007 (W5254, ELM W03187); East London, H. Burnup Coll'n (B0032); ditto, Umtiza Nat. Res. (33.016[degrees]S:27.809[degrees]E), 160 m, coastal forest, in leaf-litter, eating Chondrocyclus sp., D. Herbert & M. Bursey, 4/iii/2000 (V7904); ditto (33.016[degrees]S: 27.809[degrees]E), coastal indigenous forest, under log, A. Moussalli & D. Stuart-Fox, 26/xi/2005 (W4182, W5466); ditto, (33.01444[degrees]S:27.80806[degrees]E), forest, in leaf-litter, R. Botha, 07/ii/2007, don. M. Bursey (W5253, ELM W03208).

Additional literature records (material not seen): SOUTH AFRICA: E. Cape: Coega (Pace 1895); Port Alfred (fide Crawford, Connolly 1939).

Distribution (Fig. 72): Endemic to E. Cape Province. Recorded from the GrahamstownPort Alfred region east to East London, with one additional literature record from Coega, near Port Elizabeth (Pace 1895); from sea level to approx. 500 m in the Grahamstown area.

Records from the Somerset East-Cradock area given by Connolly (1912) were almost certainly based on misidentified A. knysnaensis material (see also Schileyko 2000, fig. 971). He later omitted these records (Connolly 1939), suggesting that he had become aware of this error. An old radula slide in the NMSA labelled 'Natalina trimeni, Cradock', clearly represents the radula of a specimen of A. knysnaensis.

Habitat: The limited habitat data available suggests that A. trimeni is primarily an inhabitant of indigenous forest; in leaf-litter and under logs.

Notes: Analysis of molecular sequence data (Moussalli et al. 2009) indicates that material from East London, previously known under the name Natalina arguta Melvill & Ponsonby, 1907 shows little genetic divergence from Afrorhytida trimeni. Likewise there are no discernable differences in the radula. The reported differences in shell characters, namely more distinct axial sculpture on the base, wider umbilicus and smaller size in A. arguta (Connolly 1939), appear to be consistent in the limited material available, but such differences could easily be accommodated within the variation of a single species. The colour difference mentioned by Melvill and Ponsonby (1907), namely olivaceous (trimeni) vs rufous-brown (arguta), is not apparent in the specimens available. The disparity in size appears to be the most striking difference between the two populations. Two evidently mature shells from East London (Umtiza Nat. Res.), each comprising ca 4.75 whorls, measure 19.7 mm and 20.3 mm in diameter, compared to 25.5 mm for a shell from Hamburg also comprising ca 4.75 whorls. The largest shell available from the East London area is 22.0 mm in diameter (ELM D15190), whereas many mature shells from other regions are larger than this. However, given that the East London material is genetically very close to that from other regions (Moussalli et al. 2009 and Fig. 1 herein), it may be that the size difference relates to undetermined ecological factors. While acknowledging that this is an issue which needs further investigation, we consider it unlikely that the two nominal taxa represent specifically distinct entities and place the name Natalina arguta in synonymy with A. trimeni. The most that could be justified would be to recognise the junior name as an eastern subspecies of smaller size, but we refrain from doing this on account of the limited material available, much of which is juvenile or subadult.

[FIGURE 72 OMITTED]

Conservation: The distribution of Afrorhytida trimeni is somewhat limited, but not highly restricted. Its range spans 230 km in the coastal region and extends up to 40 km inland, but given that it appears to favour forest habitats, its distribution within this range is likely to be fragmented. There are relatively few formally protected conservation areas within this area, but populations are known from both Umtiza and Kap River provincial nature reserves. The preservation of southern coastal forest and southern mist-belt forest habitat within the broader Albany Thicket biome (Mucina & Rutherford 2006) would appear to be important for the conservation of this species.

Genus Capitina Watson, 1934

Capitina: Watson 1934: 153. Type species: Helix scharfiae [= schaerfiae] Pfeiffer, 1861, by original designation.

Diagnosis: Shell of moderate size (adult diameter up to 34 mm), discoidal to globoselenticular, usually with distinct spiral colour pattern; sculptured by anastomosing axial riblets producing a somewhat pitted or wrinkled sculpture; outer lip slightly thickened and without periostracal fringe; peristome interrupted in parietal region; umbilicus open, width moderate; protoconch of 1.25-1.5 whorls, with close-set axial riblets (Fig. 4C) and often with traces of spiral sculpture, diameter 4.0-7.0 mm. Radula possessing rachidian tooth; no clear distinction between lateral and marginal series and no one tooth noticeably larger than the others. Mantle lobe to left of pneumostome undivided. Penis very long, situated to left of retractor muscle of right optic tentacle; epiphallus short (<25 % of penis length); epiphallus and lower vas deferens connected to penis by connective tissue web; vagina very long; oviduct caecum absent. Distal part of suprapedal gland sinuous but not convoluted, lacking a swollen terminal vesicle.

External anatomy (Fig. 76): Left body lobe of mantle undivided, forming a continuous skirt over neck region (Fig. 6B); skin texture finely to moderately granular; labial palps present but not large; optic and inferior tentacles with a ventrally distended apical bulb; tail region of foot relatively short; genital pore ventral and just posterior to right optic tentacle; lung venation strongly delineated by black pigmentation.

Radula (Fig. 73): Formula 1+(20-32); length up to 15.5 mm, with up to 84 V-shaped transverse rows of teeth, 5.0-6.6 rows/mm in adult; no clear distinction between lateral and marginal series. Rachidian present, with a relatively short, broad cusp, one quarter to one third length of base-plate; remaining teeth (laterals and marginals), elongate and slender, progressively (slowly) increasing in size, those in middle of lateromarginal series largest, then decreasing in size somewhat more rapidly toward edge of radula, the outermost tooth being minute; inner teeth claw-like, with a relatively short, weakly curved, broadly acuminate cusp; larger teeth in middle of lateromarginal series with a flatter, more elongate cusp, but lacking an enlarged quadrate base-plate; those peripheral to this becoming spathulate, with a rounded tip and anteriorly acuminate base-plate.

[FIGURE 73 OMITTED]

Distal genitalia (Figs 9C, 74, 75): Penis very long and slender, often sinuously folded in situ; its wall muscular, particularly towards base; internal lumen lined by papillate epithelium (Fig. 75A), papillae close-set and relatively coarse, somewhat larger toward penis base. Apex of penis with small, rounded penis papilla, through which epiphallus lumen connects with penis lumen (Fig. 75A); penis papilla itself covered with micropapillae similar to those lining the penis lumen. Epiphallus short, <25 % of penis length; joins penis at U-shaped bend where penial retractor muscle inserts; interior with longitudinal ridges lining outer wall, lying opposite a broad, rugose, tongue-shaped pilaster on inner wall (adjacent to penis) (Fig. 75B). Vas deferens runs alongside penis, vagina and free oviduct, broader and thrown into a series of bends in the latter region, before it fuses with spermoviduct. A web of connective tissue joins lower vas deferens and epiphallus to penis.

Vagina very long and slender with muscular wall; attached laterally to body wall by a well-developed series of muscle fibres; merges with free oviduct at origin of bursa copulatrix duct; interior wall of vagina with weakly crenulate, longitudinal ridges. Free oviduct expanded and thick-walled (site of spermatophore receipt), lined with smoother longitudinal ridges (Fig. 75C). Oviduct caecum absent. Bursa copulatrix duct long and slender, but not as slender as that of Natalina, running beside spermoviduct rather than within its coils; bursa copulatrix thin-walled, more or less ovate, situated posterior to pericardium. Spermoviduct relatively short, the lower half convoluted; hermaphrodite duct highly convoluted; ovotestis comprising a loose assemblage of slender acini, embedded in apical whorl of digestive gland.

Spermatophore (Figs 10A, 76): A single allospermatophore was found in a specimen of Capitina calcicola sp. n. collected in early October. It was in good condition, suggesting recent copulation and thus that mating occurs in spring, at least. Spermatophore tadpoleshaped (straightened length 8.2 mm) and situated in swollen, thick-walled, lower portion of free oviduct. Head of spermatophore foremost, lying close to origin of free oviduct from spermoviduct, tail curving downward into opening of bursa duct. Spermatophore head pale orange-pink and hard, with numerous irregular, sometimes sinuous, longitudinal ridges; underside of the head concave, corresponding to tongue-like pilaster in epiphallus; internal contents of spermatophore head whitish; tail considerably thinner and without pink coloration or internal contents. No obvious vent evident, but central portion of concave underside of head thin-walled and possibly representing rupture site.

[FIGURE 74 OMITTED]

[FIGURE 75 OMITTED]

[FIGURE 76 OMITTED]

Notes: The phylogenetic analysis of morphological characters and DNA sequence data published by Moussalli et al. (2009) has shown that Capitina represents a highly distinctive lineage within Natalina s. l. As a result, we have proposed that the taxon be ranked as a genus in its own right. In terms of shell features, Capitina is characterised by the brown spiral lines on the adapical surface, wrinkled sculpture and thickened apertural lip of the adult. In addition, Capitina exhibits a number of distinct anatomical character states associated with the mantle edge, radula and distal genitalia which clearly distinguish it from Natalina and Afrorhytida.

The distribution of the genus is confined to the southern part of the south-western Cape and appears not to overlap with that of either Natalina (2) or Afrorhytida. It is the only genus of relatively large rhytidids known from the south-western Cape, west of 20[degrees]E. This, combined with the basal split between Capitina and (Natalina + Afrorhytida) (Moussalli et al. 2009) suggests that Capitina stems from an early divergence event which divided the ancestral Natalina s. l. stock into western and eastern lineages. Using a conservative mutation rate of 5 % pairwise, mtDNA sequence data places this basal split in the mid-Miocene (Moussalli et al. 2009). However, Spencer et al. (2006) suggested an even slower rate for COI evolution within the New Zealand rhytidid radiation, and there is thus a possibility that the initial split within Natalina s.l. may date from as far back as the early Miocene (Moussalli et al. 2009). It is interesting to note here in terms of an ancestral reconstruction, that the radula of Capitina is closer to that of the Australian Strangesta Iredale, 1933 (Smith 1979) and New Zealand Schizoglossa Hedley, 1892 (Powell 1930) than it is to either Natalina or Afrorhytida. However, such similarities may be diet-related homoplasies and need to be interpreted with caution.

When proposing Capitina as a new taxon, Watson (1934) included in it only 'Natalina' schaerfiae, but noted the existence of light coloured specimens which Layard (in Benson 1864) had suggested were simply pale varieties or bleached specimens of the same species. Watson, however, observed additional differences in sculpture, shell proportions and protoconch size, and speculated that these specimens may ultimately prove to belong to a second and unnamed taxon. With considerably more material available and accurate locality data we are able to confirm Watson's observations and here describe this paler lineage as a new species.

The Agulhas Plain, to which this new species is limited, has experienced repeated Neogene marine transgressions of up to 200 m, with sea levels retreating to present levels only as recently as 2 Mya (Siesser & Dingle 1981; Linder 2003). Such transgressions may have constituted an effective isolating mechanism, restricting ancestral Capitina populations to refugial foci in the Riviersonderendberge and at higher elevations on the Agulhas Plain, facilitating divergence within the ancestral stock. This is consistent with a Late Pliocene estimate for the divergence of the two lineages based on COI sequence data (unpubl. data).
Key to species of Capitina

1  Shell brown with darker brown spiral lines; periostracum
   well-developed; apex low (H:D=0.48-0.53) and shell thin; protoconch
   diameter 6.0-7.0 mm; radula with ca 30 teeth per half row.
   Riviersonderendberge                                  C. schaerfiae

-- Shell typically pale usually with bold, darker brown spiral
   lines; periostracum weakly developed; apex higher (H:D=0.58-0.70)
   and shell somewhat thicker; protoconch diameter 4.0-5.3 mm; radula
   with ca 20 teeth per half row. Agulhas Plain    C. calcicola sp. n.


Capitina schaerfiae (Pfeiffer, 1861)

Figs 4C, 7C, 9C, 11A, 73A, B, 77, 78A, 79, 81

Helix scharfiae: Pfeiffer 1861: 73, pl. 2, figs 1-3; 1868: 242; Benson 1864: 494. Type loc.: Bredas Bosch, near Genadendal, W. Cape [Madame Scharfj. [scharfiae emended to schaerfiae following ICZN (1999), Art. 32.5.2.1]

Macrocyclis schaerfiae: Pfeiffer 1878 in 1878-81: 62.

Helix (Ampelita) schaerfiae: Pfeiffer 1879 in 1878-81: 184.

Helix schaerfiae: Kobelt 1886 in 1877-97: 615, pl. 178, figs 1-6.

Helix (Ampelita) schaerfiae: Pilsbry 1890 in 1890-91: 43, pl. 7, figs 95-97, 1, 2.

Rhytida schaerfiae: Melvill & Ponsonby 1898: 170.

Macrocyclis schaerfiae: Sturany 1898: 33.

Natalina schaerfiae: Connolly 1912: 96 (in part); 1939: 116, pl. 4, figs 6-8, text-fig. 10 (in part); Barnard 1951: 142, pl. xxi, fig. 8.

Tulbaghiniaschaerfiae: Connolly 1915: 174.

Natalina (Capitina) schaerfiae: Watson 1934: 153, pl. 19, figs 1-4.

Etymology: Named for 'Madame Sophie Scharf', perhaps connected with the Moravian Mission at Genadendal (Barnard 1965).

[FIGURE 77 OMITTED]

Identification: More depressed and thinner-shelled than Capitina calcicola sp. n., and with a larger protoconch; umbilicus not obscured to any appreciable extent by reflected columella lip; periostracum darker and more obvious; spiral colour pattern usually less bold.

Description (Fig. 77): Shell lenticular to discoidal, spire low; comprising up to 4.5 whorls, last adult whorl expanding relatively rapidly and descending noticeably prior to aperture; apical surface lustreless, base glossy. Protoconch diameter 6.0-7.0 mm; sculptured primarily by close-set axial riblets (Fig. 4C), strongest adapically, but traces of spiral threads may also be present, particularly near periphery. Teleoconch sculptured initially by close-set axial riblets, these becoming less distinct with growth and tending to anastomose, producing a pitted or wrinkled sculpture; this sculpture evanescing at periphery, base smoother and more glossy with only weak growth-lines and fine spiral lirae. Aperture obliquely ovate-reniform; outer lip weakly, but distinctly thickened, white; basal lip almost straight in basal view; umbilicus of moderate width, not appreciably obscured by reflected upper part of columella lip.

Ground colour yellowish brown to mid brown with darker brown spiral lines, one line just above periphery usually more distinct; lines finer on base and usually absent in peri-umbilical area; periostracum relatively well developed, but not extending beyond aperture lip at maturity, honey-brown in fresh shells, though appearing darker in living specimens.

Dimensions: Largest specimen (NMSA B0031, Oubos), diameter 31.6 mm, H:D of adults 0.48-0.53 (N=6).

Living animal (Fig. 78A): Head-foot grey or brown to dark grey-brown, sometimes paler laterally and beneath shell; pedal margin tinged with or distinctly orange, orange colour usually more extensive on tail; tentacles generally greyish; paler longitudinal bands on neck not evident; mantle edge a darker shade of main body colour.

Radula (Figs 73A, B): See generic description; formula 1+--30 (N=2).

Type material: Originally in Szczecin (Stettin) Museum [H. Dohrn collection], Poland (Connolly 1912). Although Dance (1986) stated that the Dohrn collection was totally destroyed in the Second World War, we have established through Furth et al. (1994), that some entomological material from

the Stettin Museum was transferred to the Museum and Institute of Zoology, Polish Academy of Sciences, Warsaw. Further enquiries have led to the discovery of a specimen labelled 'Helix scharfiae' at the latter institution. This almost certainly represents a shell from the original sample and indicates that some Stettin Museum molluscan material was transferred to the Institute of Zoology and is still extant. We designate this specimen as lectotype (Figs 77A, B).

[FIGURE 78 OMITTED]

Material examined: SOUTH AFRICA: W. Cape: Riviersonderendberge, Oubos (Oudebosch) (NMSA B0031 ex SAMC, BMNH 1937.12.30.1309-10); ditto (34.07702[degrees]S:19.82884[degrees]E), 370 m, Afrotemperate forest, in leaf-litter and under logs, D. Herbert & L. Davis, 11/x/2007 (NMSA W5672); 'Swellendam' ex E.L. Layard, purchased from Sowerby & Fulton, 1919 (NMSA 3125).

Distribution (Fig. 79): A narrow-range W. Cape endemic, known only from the southern slopes of the Riviersonderendberge. We consider records from Swellendam to be highly dubious. They relate to old specimens purchased from Sowerby & Fulton and the provenance given may simply refer to a then more well-known locality in the general area of occurrence. Records from the Bredasdorp area (Connolly 1912, 1939) refer to the following species.

Habitat: Capitina schaerfiae has been found only in patches of southern Afrotemperate forest in valleys on the south-facing slopes of the Riviersonderendberge. At Oubos [Oudebosch], where the material studied by Connolly and Watson originated, the species remains common, living under logs and forest floor debris (altitude 350-400 m).

Notes: In addition to being thinner-shelled, more depressed and generally less boldly marked than Capitina calcicola sp. n., in the present species the protoconch is larger, the head-foot darker and the radula has more teeth per row. Further comparative details are given under C. calcicola.

Conservation: The available data suggest that the distribution of Capitina schaerfiae is both fragmented and highly restricted. Its range in the Riviersonderendberge is essentially linear, and covers a west-east distance of only approx. 65 km. Even within this it evidently occurs only in forest fragments. The only locality at which it has been recorded within the last 50 years is at Oubos, where, for a moderately large predatory species, it seems to be relatively common. More field surveys are needed in order to clarify the current extent of its range, but it seems probable that other populations remain in forested valleys elsewhere on the southern slopes of these mountains. The area is not well sampled.

[FIGURE 79 OMITTED]

Large parts of the Riviersonderendberge fall within conservation areas (Greyton Nat. Res., Riviersonderend Provincial Nat. Res. and Riviersonderend Mountain Catchment Area) and are thus afforded some degree of protection.

Capitina calcicola sp. n.

Figs 6B, 8C, 10A, 73C, D, 74, 76, 78B, 79-81

Natalina schaerfiae [non Pfeiffer, 1861]: Connolly 1912: 96 (in part); 1939: 116 (in part), pl. 4, figs 9-11. Natalina (Capitina) schaerfiae: Watson 1934: 153 (in part); Schileyko 2000: fig. 972A.

Etymology: From Latin calx (lime) and cola (an inhabitant); referring to its occurrence in calcium-rich habitats.

Identification (Fig. 80): Capitina calcicola is a distinctive taxon easily separated from C. schaerfiae by its paler, more elevated, thicker shell, frequently with a bolder spiral colour pattern. In addition, the sculpture is somewhat coarser, the protoconch smaller (diameter 4.0-5.3 mm), the head-foot coloration more orange and the radula has fewer teeth per transverse row.

Description: Shell subglobose to lenticular, spire low; comprising 4.5-5.0 whorls when adult; last adult whorl descending prior to aperture; apical surface lustreless, base glossy. Protoconch diameter 4.0-5.3 mm, sculptured by axial riblets, strongest below suture, and increasing in strength toward end of final whorl; one or more weak incised spiral lines may be present just above abapical suture/periphery, but these sometimes scarcely evident. Teleoconch with similar axial riblets, these interacting with irregular spiral elements to produce a pitted or wrinkled sculpture; this sculpture evanescing at periphery and base smoother and more glossy with only weak growth-lines and fine spiral lirae. Aperture variable in shape, generally obliquely ovate-reniform; outer lip weakly, but distinctly thickened, white; interior of aperture sometimes with a thickened subsutural spiral ridge set back some distance behind outer lip, a second similar ridge present on upper part of parietal lip, the two delimiting a distinct groove underlying the suture (this feature present only in adult specimens and then only in some individuals); umbilicus of moderate width, partially obscured by upper, reflected portion of columella lip. In sub-adult specimens (Fig. 80J) the basal and columella lips show some thickening, but the upper outer lip remains thin and descends only slightly, the thickening of the columella lip is also not completed and the umbilicus is therefore less obstructed.

Shell whitish, overlain by a pale straw-brown to light honey-brown periostracum; apical surface patterned with spiral lines of differing width, in various shades of brown, one or two lines just above periphery usually more distinct; lines weaker on base and usually absent in peri-umbilical area; periostracum not extending over aperture lip at maturity.

Dimensions: Holotype: diameter 28.0 mm, height 17.2 mm; largest specimen (NMSA W5670/T2265, Grootbos Nat. Res.), diameter 33.6 mm; H:D of adults 0.58-0.70 (N=22).

Living animal (Fig. 78B): Head-foot pale apricot to bright orange or brown, usually paler laterally and beneath shell; pedal margin and tail often slightly more intensely coloured; tentacles somewhat paler or more greyish; no pale longitudinal bands evident on neck; mantle edge darker orange-brown.

Radula (Figs 73C, D): See generic description; formula 1+~20 (N=3) in adult, juveniles with fewer teeth in lateromarginal series.

Holotype (Figs 80A-C): SOUTH AFRICA: W. Cape: Die Dam region (34.7487[degrees]S:19.6708[degrees]E), coastal fynbos, A. Moussalli & D. Stuart-Fox, 14/ii/2005 (NMSA W6265/T2262).

Paratypes: SOUTH AFRICA: W. Cape: same data as holotype (NMSA W3354/T2276, 1 specimen; W3355/ T2264, 5 specimens); Gansbaai (34.5794[degrees]S:19.3442[degrees]E), coastal dune scrub, dormant, buried in sand under vegetation, A. Moussalli & D. Stuart-Fox, 13/ii/2005 (NMSA W3201/T2269, 4 specimens; W3368/T2263, 1 specimen; W3369/T2268, 1 specimen); Gansbaai area, Grootbos Nat. Res. (34.53402[degrees]S:19.43480[degrees]E), 330 m, limestone fynbos, under vegetation beside rocks, D. Herbert & L. Davis, 08/x/2007 (ELM D15856, 2 specimens; BMNH 20100127, 1 specimen; NMSA W5670/T2265, 29 specimens; RMNH.MOL.121374, 1 specimen); Pearly Beach area, Bantamsklip (34.674772[degrees]S:19.590264[degrees]E), limestone hills, at base of or in restios, M. Picker, 29/ix/2007 (NMSA W5998/T2266, 3 specimens); Cape Agulhas (34.8293[degrees]S:19.9854[degrees]E), coastal dune scrub, buried deep in sand under small bush, A. Moussalli & D. Stuart-Fox, 14/ii/2005 (MVM F167491, 1 specimen; NMSA W3360/T2270, 1 specimen; W3365/T2267, 8 specimens); Cape Agulhas, V. Fitzsimons, x/1940, ex Transvaal Museum (NMSA 3978/T2271, 1 specimen); Bredasdorp, E.L. Layard (BMNH 1937.12.30.1311-13, 3 specimens).

[FIGURE 80 OMITTED]

Additional material examined (all NMSA unless otherwise indicated): W. Cape: Hermanus, Maanskynkop (SAMC A8174); Gansbaai, M. Picker, 06/ix/2003 (W4854); Gansbaai area, Grootbos Nat. Res. (34.54205[degrees]S: 19.41529[degrees]E), 215 m, milkwood forest, dead in leaf-litter, D. Herbert & L. Davis, 07/x/2007 (W5664); ditto (34.54063[degrees]S:19.41318[degrees]E), 217 m, milkwood forest, in sandy leaf-litter, A. Moussalli & D. Stuart-Fox, 13/ ii/2005 (W5421); ditto (34.54135[degrees]S:19.43871[degrees]E), 325 m, Afrotemperate forest, in leaf-litter and under logs, D. Herbert & L. Davis, 08/x/2007 (W5919); Bredasdorp area, Soetendalsvlei, ex Transvaal Museum (B7315); l'Agulhas, in macchia veld, J.S. Taylor, 22/viii/1964 (4122); Cape Agulhas (34.8293[degrees]S:19.9854[degrees]e), coastal dune scrub, buried deep in sand under small bush, A. Moussalli & D. Stuart-Fox, 14/ii/2005 (W3359); Bredasdorp District, Prof. de Villiers (BMNH 1937.12.30.1314-16).

Distribution (Fig. 79): Endemic to the Agulhas Plain, recorded only from the coastal region between Hermanus and Cape Agulhas, W. Cape. Records from Bredasdorp (e.g., Connolly 1939: pl. 4, figs 9-11), although perfectly plausible, require confirmation since all are early records and may simply cite the town due to its being the nearest well-known settlement. Recorded at altitudes from sea level to 330 m. Habitat: Occurs primarily in coastal fynbos habitats (Agulhas Limestone fynbos and western Overberg dune strandveld, sensu Musina & Rutherford 2006), and can be common in limestone areas. Dead shells have also been found in coastal milkwood (Sideroxylon) forest, but much less commonly so. In the dry season the animals bury themselves deeply in sandy soil/litter beneath shrubs, but can be found on the surface beneath plants during wetter periods.

Notes: Capitina calcicola differs clearly and consistently from C. schaerfiae. Its shell is paler and more elevated (H:D=0.58-0.70 compared with 0.48-0.53 in C. schaerfiae, see Fig. 81), and the spiral colour bands are generally darker and more pronounced (excepting occasional weakly patterned individuals). In addition, the protoconch is smaller (diameter 4.0-5.3 mm, compared with 6.0-7.0 mm in C. schaerfiae), the body coloration is paler and of a more orange hue, and the radula has fewer teeth (approx. 20 per half row compared to approx. 30 in C. schaerfiae). C. calcicola is also generally thickershelled (perhaps due to the presence of environmental limestone) and the periostracal layer is paler and thinner, tending to flake off after death; it is however certainly present in living specimens (cf. Connolly 1939).

[FIGURE 81 OMITTED]

Since these differences are considerable and include features of the protoconch, teleoconch and radula, we believe they are sufficient to warrant recognition of the two taxa as separate species. Molecular data likewise separate the two taxa (Moussalli et al. 2009), although at present, the level of genetic divergence between the two is difficult to assess given the limited number of specimens sequenced to date. This remains a topic needing to be investigated more thoroughly through the collection and sequencing of further samples of both species from additional localities, particularly for C. schaerfiae.

Conservation: Although not as narrowly endemic as C. schaerfiae, C. calcicola sp. n. too is evidently a species of restricted range. The known extent of occurrence is approx. 2500 km2. It is recorded from or likely to occur in several formally protected areas and private nature reserves (Cape Agulhas National Park, Walker Bay Provincial Nat. Res. and Grootbos Private Nat. Res.). The continued preservation of pristine limestone fynbos habitats in the western Agulhas Plain is crucial to the on-going survival of this taxon. In this regard, habitat transformation resulting from the invasion of exotic Acacia species represents a potential threat.

BIOGEOGRAPHIC SUMMARY

Rhytidid snails represent a characteristic element of the palaeogenic invertebrate fauna of southern Africa (Stuckenberg 1962). The family is thought to be of Gondwanan origin and part of what Solem (1959) termed the 'southern relict fauna'. However, the Rhytididae has a somewhat restricted distribution within fragmented Gondwana, with representatives occurring only in southern Africa, Australasia and islands in the southwestern Pacific (supposed rhytidids occurring in E. Africa, the Seychelles and Madagascar belong to other families, see Introduction). Strangely, they are absent from that part of Gondwana with which Africa had its most recent contact, namely South America (although their relationship to the South American Systrophiidae, which are also often included in the Rhytidoidea, needs to be further explored). A similar Gondwanan distribution that excludes South America is evident in sphaerotheriid millipedes and suggests an origin in eastern Gondwana (Wesener & VandenSpiegel 2009). However, sphaerotheriid millipedes are also known from India, Madagascar and south-east Asia, whereas rhytidid snails are not. The absence of rhytidids from the latter regions implies that their pre-fragmentation distribution in eastern Gondwana did not include those parts of the African plate abutting the Indo-Malagasy plate. This is consistent with the fact that, within Africa, rhytidids are [remain] restricted to the extreme south and southeast of the continent. The African distribution of peripatopsid Onychophora is similarly confined to this region, and they are also absent from India-Madagascar and south-east Asia, but unlike rhytidids and sphaerotheriids, the peripatopsids also occur in South America. Although the present-day global distribution of each of these low-vagility, Gondwanan invertebrate groups comprises a different assemblage of Gondwanan continental fragments, this does not detract from their hypothesised Gondwanan origins and probably strongly relates to the distribution of respective groups in pre-fragmentation Gondwana.

Within south-east Africa, the larger rhytidids are limited to those regions south and east of the Great Escarpment (Fig. 82) and the same is true for the smaller species (Nata s. l.), although new distribution data indicate that the latter penetrate further inland than indicated in the map provided by Bruggen (1978), further even than Natalina s. l. (unpubl. data). The north-eastern family boundary is defined by the low-lying Limpopo Valley, a geomorphic feature already in existence in the Cretaceous (Partridge & Maud 1987) and an effective biogeographic barrier since the early Tertiary (Stuckenberg 1962). Only at the coast has the family crossed this barrier, and then only marginally so. The range of the related chlamydephorid slugs and the African peripatopsid Onychophora is similarly restricted by the Great Escarpment (Hamer et al. 1997; Herbert 1997), but unlike the peripatopsids and rhytidids, the distribution of the chlamydephorids extends to the eastern highlands of Zimbabwe. African sphaerotheriid millipedes, though also largely confined to south-eastern Africa, range still further north, reaching Malawi (Wesener & Van den Spiegel 2009). It is possible that the restriction of these groups to the south and east of southern Africa is linked to the distribution of forests, but while this may have been true historically, it is not currently the case for either rhytidids or chlamydephorids as representatives of both occur in non-forest habitats such as open thicket and savannah, and even fynbos in the case of rhytidids.

Molecular evidence suggests that cladogenesis within Natalina s. l. probably predates the Pliocene (Moussalli et al. 2009) and may have been associated with major drying, contraction and fragmentation of mesic habitat in sub-Saharan Africa commencing in the mid-Miocene and extending into the Plio-Pleistocene, a phenomenon known to have had important evolutionary implications for many components of the regional biota (Mucina & Rutherford 2006; Tolley et al. 2008, 2009). The first lineage divergence appears to have split the ancestral stock into western (Capitina) and eastern lineages (Afrorhytida and Natalina). The boundary between the two is coincident with that between western (winter rainfall) and eastern (year-round rainfall) components of the Cape Floristic Region (CFR), in the region of the Breede River (Cowling & Richardson 1995) (Fig. 83), although the range of one Afrorhytida subspecies (A. kraussi oraria) lies just within the western CFR. Based on the present-day distribution of Capitina, this western lineage appears not to have crossed the Hottentots-Hollands Mountains (a sub-boundary within the western CFR), unlike Nata s.l., the other southern African rhytidid radiation. Capitina remains an isolated lineage restricted to the AgulhasOverberg region (the Bredasdorp Centre of plant endemism). Its distribution does not overlap with either Afrorhytida or Natalina. In contrast, the current distributions of Afrorhytida and Natalina overlap extensively (Fig. 82) and each has undergone moderate radiation in the year-round and summer rainfall regions south and east of the Great Escarpment.

[FIGURE 82 OMITTED]

Afrorhytida occurs only in the southern and eastern Cape, and the dominant biogeographic pattern is one of an west-east species turnover (Fig. 83). Afrorhytida kraussi occurs in the eastern CFR, reaching its easternmost limit just west of Port Elizabeth. East of this it is replaced by A. knysnaensis, the turnover zone being more or less coincident with the boundary between the Fynbos and Albany Thicket biomes (Mucina & Rutherford 2006), in the region of the Uitenhage Basin. A. knysnaensis is the sister taxon of A. kraussi from which it may have diverged due to selection pressures associated with the increasingly open and drier habitats emerging during the Plio-Pleistocene aridification. Certainly, A. knysnaensis is now more tolerant of drier conditions than is A. kraussi, and its distribution extends a considerable distance further inland, essentially tracking the Albany Thicket biome, a recognised centre of endemism for plants (van Wyk & Smith 2001), molluscs (Govender 2007) and millipedes (Hamer & Slotow 2002).

To the east, A. burseyae replaces A. knysnaensis at the boundary between the Albany Thicket and the southern parts of the Grassland and Savannah biomes. Their distributions coincide also with river catchments, A. knysnaensis occurring in the Sundays and Great Fish catchments and A. burseyae, largely in the Kei and Mbashe catchments. It appears therefore that for these two non-forest species, it is the catchment boundaries that may be the limiting biogeographical features in this instance. Although these two taxa are not sister species and the boundary between the Great Fish and Kei catchments therefore not a vicariant feature contributing to speciation, it may well now limit dispersal and maintain the allopatry of these lineages. The high altitude, open grassy habitats of the Winterberge and Amathole Mountains could be an effective barrier to dispersal in the inland region. Although river catchments often define species boundaries in freshwater groups, they are rarely cited as being significant for fully terrestrial taxa, but Price et al. (2007) have postulated similar catchment-delimited boundaries between lineages of the cicada Platypleura stridula (L., 1758) in the south-western Cape. Relative to the preceding Afrorhytida species, A. trimeni has a more restricted range, limited to the coastal region of the Albany Thicket. It is not, however, a thicket species, occurring instead in forest patches within the broader thicket biome and thus its distribution is limited to the higher rainfall coastal regions suitable for forest persistence.

Phylogenetic diversity within Afrorhytida is evidently considerable, as indicated by the relatively deep divergence of the major clades and long branch lengths subtending the terminal taxa in all lineages except A. trimeni (Fig. 1). This suggests that the lineages are relatively old, and that gene flow within them has been historically interrupted (less so in A. trimeni), in which case phylogeographical substructure should be evident (e.g., A. kraussi). Alternatively, high within-clade diversity without obvious geographical substructure (A. knysnaensis) may result from the persistence of a single large or several well connected populations combined with the retention of ancestral polymorphisms. Additional fine-scaled molecular analysis with greater specimen representation is needed to resolve these competing hypothesis.

The distribution of Natalina overlaps extensively with that of Afrorhytida in Eastern Cape, but extends much further to the north-east, reaching the Limpopo River valley in southern Mozambique. The most basal divergence is that of the morphologically distinct N. (Tongalina) wesseliana, the only Natalina lineage occurring in the subtropical north-eastern coastal region (Fig. 84). Its distribution closely matches that of the Maputaland centre of endemism (van Wyk & Smith 2001). However, whereas most species endemic to this centre are of Afrotropical origin (van Wyk & Smith 2001), N. wesseliana is clearly derived from southern stock. Since the forests of the Indian Ocean Belt are thought to have expanded in to this region only after the last Glacial Maximum (Eeley et al. 1999; Lawes et al. 2007), it seems probable that N. wesseliana, a largely forest-dependent species, persisted as relict populations along the coastal scarp in northern Zululand during the last hypothermal, expanding northwards and coastwards as forest cover increased. Although represented by relatively few individuals in our molecular phylogeny, there is some geographic substructure within this clade which, combined with the comparatively long branch lengths, suggests some historical interruption in gene flow and fragmentation of the refugial population.

Subsequent cladogenesis within Natalina (i.e. within Natalina s. s.) resulted in the evolution of two distinct lineages, the small-shelled N. quekettiana complex and the large-shelled N. cafra-beyrichi clade. The distribution of the former is tied to the forest biome along the north-eastern section of the Great Escarpment, extending to lower altitude mist-belt and scarp forests (Fig. 84), and mirrors a pattern evident in the forest-dependent dwarf chameleons (Bradypodion spp.) of KwaZulu-Natal and the northern Drakensberg (Tolley et al. 2004, 2006). The basal divergence of the two montane lineages in this clade (Fig. 1) might be taken to suggest that the complex as a whole originated at high altitudes, with subsequent dispersal into mist-belt and scarp forests. However, the idea that the geographical location of the basal taxon within a clade reflects the centre of origin of that clade is controversial. Sequential localised differentiation within a widespread ancestral population may achieve a similar result (Heads 2009). In this case, dispersal from montane forests to mist-belt and scarp forest would run counter to the general pattern evident in eastern South Africa, i.e. post-Last Glacial Maximum (LGM) dispersal from scarp forest refugia into higher altitude forests (Lawes et al. 2007). Although, under such a scenario one might expect the lineages in the lower altitude forests to be basal. In fact, given the considerable genetic divergence evident within this clade, it seems likely that the early divergence of both montane lineages considerably predates the LGM (estimated to date from the Pliocene based on the conservative 5 % mutation rate for mtDNA used here--see Moussalli et al. (2009) for further detail). Thus the branching pattern evident in this group probably reflects sequential vicariant cladogenic events resulting from repeated expansion and contraction of Afrotemperate forests during the Plio-Pleistocene, perhaps from lower altitude scarp forest refugia. Evidently the forests in the Cathedral Peak-Injasuthi area have persisted through these climatic fluctuations, retaining lineages from previous interglacial expansions. The fact that these forests also contain narrow-range, forest-dependent chameleons (Tolley & Burger 2007), spiders (Griswold 1985) and achatinid snails (Bruggen 1965) provides further support for their long term persistence. Millipedes of the genus Doratogonus Attems, 1914, show similar narrow-range endemism associated with high altitude forests in the KwaZulu-Natal Drakensberg (Hamer 2000), although it is not clear whether the species concerned constitute a monophyletic lineage.

[FIGURE 83 OMITTED]

[FIGURE 84 OMITTED]

With regard to the Natalina cafra-beyrichi complex, the low levels of phylogenetic diversity evident in this clade point to relatively recent radiation (Moussalli et al. 2009 and Fig. 1). The primary divergence within this complex relates to a cladogenic event in the north-eastern E. Cape, separating well-supported, north-eastern (KwaZulu-Natal) and southern (E. Cape) lineages (Fig. 1). N. beyrichi then diverged from the main E. Cape lineage in the Pondoland region (Fig. 84), an area known to be rich in neoendemics of Cape origin (van Wyk & Smith 2001) and a focus of endemism in other molluscan genera (Bursey & Herbert 2004; Govender 2007; Cole & Herbert 2009). Subsequently, the remaining E. Cape N. cafra stock has diverged in to three further lineages. One is an ecologically tolerant form that is broadly distributed in the more mesic southern parts of the Albany Thicket (N. cafra cafra), whereas the other two are generally (though not exclusively in the case of N. cafra eumacta) associated with forest habitats in the Amathole Mountains (N. cafra amathole) and the East London-southern Transkei coastal belt (N. cafra eumacta). The forests in the Amathole region are known to contain additional narrowly endemic, forest-dependent taxa belonging to other low-vagility groups, e.g., forest floor spiders (Microstigmata amatola Griswold, 1985) and frogs (Anhydrophryne rattrayi Hewitt, 1919). These forests straddle the catchment boundary between the Kei River on the one hand and the Great Fish River and smaller coastal catchments (Keiskamma and Buffalo) on the other. Griswold (1985) considered the deep, relatively arid and thicket-filled valleys of these two large drainage systems to be important barriers, isolating the forests and forest-associated animals of the Amathole Mountains. Significantly, his work on the spider genus Microstigmata (Griswold 1985) revealed a similar spatio-temporal pattern of cladogenic events, with the KZN species occupying basal positions relative to a younger radiation in E. Cape, which in turn has foci of distribution west of the Great Fish River, in the Amathole Mountains, and in Transkei. Given these concordant patterns, it is possible that the basally divergent N. cafra natalensis represents a separate, highly cryptic species.

From the above biogeographic summary, it is evident that the spatial distribution of all the species and subspecies under consideration is correlated and congruent with the broader patterns of floristic endemism in the southern Africa, south and east of the Great Escarpment. Evidently, the historical evolutionary process that have shaped floral diversity in the region have had a similar influence on speciation in these carnivorous snails. Further studies need to focus on the more deeply divergent lineages such as Afrorhytida burseyae, A. knysnaensis, A. kraussi and the Natalina quekettiana complex, in order to improve sister-group resolution and to search for finer-level phylogeographic structuring and cryptic species. In addition, the patterns evident in Afrorhytida, Capitina and Natalina need to be compared with the growing body of information on other taxa of limited vagility (Griswold 1985; Hamer & Slotow 2000; Tolley et al. 2006; Daniels et al. 2009), so as to identify concordant spatial patterns across unrelated groups. It is these taxa with limited dispersal capacity that are likely to retain the strongest biogeographic signal reflecting historical evolutionary processes at a regional scale (Hugall et al. 2002, 2003). At a broader scale, the analysis of molecular data needs to be expanded to include a wider spectrum of genera from the broader Australasian region in order to explore Gondwanan relationships and to test whether the southern African rhytidid radiation is indeed monophyletic.

ACKNOWLEDGEMENTS

We are greatly indebted to Mary Cole (nee Bursey) (ELM) for her long-term and ongoing contribution to this research programme. For assistance in the field and provision of specimens we acknowledge in particular Linda Davis (NMSA) and Devi Stuart-Fox, as well as Adrian Armstrong (Ezemvelo KZN Wildlife), Wesley Berrington (Van Staden's N.R.), Richard Cowling, Michael Cunningham, Michelle Hamer, D-J. Hodgkinson, Johanna Horn, Amanda Lane, Caryl and Bart Logie, Georgio Lombardi (Vogelgat N.R.), Victor Ndibo (ELM), Brummer Olivier (Grootbos N.R.), Krystal Tolley (SANBi), Charmaine Uys, Mike Wigley and the South Africans Hidden Species project (Earthwatch Institute). For the loan of specimens and access to collections we thank Jon Ablett and Kathie Way (BMNH), Thierry Backeljau (ISNB), and Liz Hoensen (SAMC). For photographs of type specimens we are indebted to Ronald Janssen and Eike Neubert (SMFD), Barbara Buge and Virginie Heros (MNHN), Thomas von Rintelin and Lothar Maitas (MNHU) and Dominika Mierzwa (Museum and Institute of Zoology, Polish Academy of Sciences). Danuta Plisko (NMSA) provided identifications of earthworm material found in crop contents. We thank the University of KwaZulu-Natal for use of the facilities at its Centre for Electron Microscopy. Linda Davis skilfully prepared the anatomical illustrations from camera lucida drawings. For reviewing and commenting on the manuscript with thank Drs Gary Barker and John Stanisic.

Material was collected under the following permits: Cape Nature, W. Cape (L5628759 and AAA007-00021-0035); Department of Economic Affairs, Environment and Tourism, E. Cape; SA Department of Water Affairs and Forestry; Ezemvelo KZN Wildlife (4674); Mpumalanga Tourism and Parks (MPV. 5109/5174); SA National Parks. Many land owners and private nature reserves in E. Cape and W. Cape have also willingly granted permission to collect specimens. This research was supported by a research grant from the South African National Research Foundation (GUN 61261) to DH and a Claude Leon Foundation post-doctoral fellowship to AM.

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Index (valid species names in bold face)

Abbreviations                                          4, 6
Afrorhytida *                                            75

  Afrorhytida burseyae *                                 98
  Afrorhytida knysnaensis *                              81
  Afrorhytida kraussi *                                  89
  Afrorhytida kraussi kraussi *                          89
  Afrorhytida kraussi oraria *                           96
  Afrorhytida trimeni *                                 103
Biogeographical summary                                 119
Biological observations
  Ecology                                                 6
  Feeding                                                 7
  Predators                                              10
  Reproductive biology                                   10
Capitina *                                              108
  Capitina calcicola *                                  116
  Capitina schaerfiae *                                 113
Comparative morphological observations
  Distal reproductive tract                              17
  Head-foot                                              12
  Mantle edge                                            14
  Protoconch                                             11
  Pulmonary anatomy                                      14
  Radula                                                 15
  Spermatophores                                         18
  Suprapedal gland                                       21
Hvperrhytida                                             75

Introduction                                              1
Materials and methods                                     4
Natalina *                                               22
  Natalina arguta (= Afrorhytida trimeni)
  Natalina beyrichi *                                    47
  Natalina cafra *                                       29
  Natalina cafra amathole *                              36
  Natalina cafra cafra *                                 31
  Natalina cafra eumacta *                               39
  Natalina cafra natalensis *                            42
  Natalina coerneyensis (= Afrorhytida knysnaensis)
  Natalina compacta (= Natalina cafra cafra)
  Natalina inhluzana *                                   66
  Natalina insignis (= Afrorhytida knysnaensis)
  Natalina liliacea (= Afrorhytida kraussi)
  Natalina quekettiana complex *                         51
  Natalina quekettiana dracomontana *                    61
  Natalina quekettiana lucaris *                         59
  Natalina quekettiana montistempli *                    64
  Natalina quekettiana quekettiana *                     54
  Natalina reenenensis *                                 67
  Natalina sturmiana (= Afrorhytida kraussi)
  Natalina wesseliana *                                  70
Tongalina *                                              69

Note: Species names in bold face indicated with *.


D. G. Herbert [1,2] and A. Moussalli [2,3]

[1] Natal Museum, P. Bag 9070, Pietermaritzburg, 3200 South Africa; dherbert@nmsa.org.za

[2] School of Biological & Conservation Sciences, University of KwaZulu-Natal, Pietermaritzburg, 3206 South Africa

[3] Sciences Department, Museum of Victoria, Melbourne, Victoria, Australia;

amoussalli@museum.vic.gov.au

(1) Pilsbry (1889) illustrated a radula with 12 lateral teeth under the name Aerope knysnaensis, but the geographical origin of the specimen was not stated (see notes below).

(2) Juvenile specimens of Trigonephrus species occurring in the Agulhas area can deceptively resemble juvenile specimens of Natalina.
TABLE 1
Summary of information concerning the diet of southern
African rhytidid snails belonging to the genera Afrorhytida,
Capitina and Natalina.

               Prey item

Higher taxon          Genus / species

Mollusca (snails)
Gastropoda            unspecified
Cyclophoridae         Chondrocyclus sp.
Achatinidae           Achatina immaculata Lamarck, 1822
                      Cochlitoma granulata (Krauss, 1848)
                      Cochlitoma vestita (Pfeiffer, 1855)
                      Metachatina kraussi (Pfeiffer, 1846)
Subulinidae           unspecified

Cerastidae            Gittenedouardia carinifera
                      (Melvill & Ponsonby, 1897)
Streptaxidae          Ennea [= Gulella] spp.
Urocyclidae           Sheldonia spp.
Helicidae             Cornu aspersum (Miiller, 1774)

                      Helix pomatia Linnaeus, 1758
Mollusca (slugs)
Veronicellidae        Laevicaulis spp.
Chlamydephoridae      Chlamydephorus gibbonsi
                      Binney, 1879
Urocyclidae           Elisolimax flavescens
                      (Keferstein, 1866)
Oligochaeta
Microchaetidae        Microchaetus papillatus Benham, 1892
                      Proandricus sp.
                      Proandricus sp.

                      Microchaetus pondoanus
                      Michaelsen, 1913

Higher taxon          Predator

Mollusca (snails)
Gastropoda            Capitina schaerfiae
Cyclophoridae         Afrorhytida trimeni
Achatinidae           Natalina cafra natalensis
                      Natalina cafra natalensis
                      Natalina wesseliana
                      Natalina cafra natalensis
Subulinidae           Natalina wesseliana

Cerastidae            Natalina beyrichi

Streptaxidae          Natalina cafra
Urocyclidae           Natalina cafra natalensis
Helicidae             Natalina cafra cafra and N.
                      cafra natalensis
                      Natalina cafra
Mollusca (slugs)
Veronicellidae        Natalina cafra natalensis
Chlamydephoridae      Natalina wesseliana

Urocyclidae           Natalina cafra natalensis

Oligochaeta
Microchaetidae        Natalina cafra natalensis
                      Natalina cafra eumacta
                      Natalina quekettiana
                      montistempli
                      Natalina beyrichi

                      Reference

Higher taxon

Mollusca (snails)
Gastropoda            Layard in Benson 1864.
Cyclophoridae         herein
Achatinidae           herein
                      herein
                      herein
                      Bruggen 1969: 14.
Subulinidae           Bruggen & Appleton 1977: 33
                      (assumed).
Cerastidae            herein

Streptaxidae          Gibbons 1880.
Urocyclidae           Herbert 1991.
Helicidae             Woodward 1895, Bruton et al. 1988,
                      Herbert 1991, Appleton & Heeg 1999.
                      Woodward 1895.
Mollusca (slugs)
Veronicellidae        herein
Chlamydephoridae      herein (freshly ingested animal
                      found in crop)
Urocyclidae           Herbert 1991.

Oligochaeta
Microchaetidae        Herbert 1991.
                      herein (found in crop)
                      herein (found partially
                      digested in crop)
                      herein

TABLE 2. Afrorhytida species, inter-specific variation in radula
formula.

Species                   Radula formula

Afrorhytida knysnaensis   1 + (7-10) + (>17)
Afrorhytida kraussi       1 + (11-15) + (11-16)
Afrorhytida burseyae      1 + (12-14) + (7-9)
Afrorhytida trimeni       1 + (13-14) + (6-9)
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Title Annotation:Revision of the larger cannibal snails (Natalina s. l.) of southern Africa--Natalina s. s., Afrorhytida and Capitina (Mollusca: Gastropoda: Rhytididae)
Author:Herbert, D. G.; Moussalli, A.
Publication:African Invertebrates
Geographic Code:6SOUT
Date:May 1, 2010
Words:15217
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