Amatholedonta bimunita ( Connolly, 1939 ) Herbert, 2020

Herbert, David G., 2020, Revision of the aperturally dentate Charopidae (Gastropoda: Stylommatophora) of southern Africa - genus Afrodonta s. lat., with description of five new genera, twelve new species and one new subspecies, European Journal of Taxonomy 629, pp. 1-55 : 21-24

Amatholedonta bimunita ( Connolly, 1939) gen. et comb. nov.

Figs 8 A–D, 9, 18C–D

Afrodonta bimunita Connolly, 1939: 256 , text-fig. 19(10), pl. 6, figs 1–4.

Afrodonta bimunita – Solem 1970: 363.

Diagnosis

Shell relatively large, deeply biconcave; protoconch with globose apical cap, smooth (diameter ±305 μm); teleoconch sculptured by distinct, close-set, compound axial riblets; intervals between riblets with numerous fine intermediary axial threads; spiral sculpture of indistinct microscopic spiral threads, usually strongest in umbilicus. Aperture narrowly lunate; parietal dentition lacking; palatal region with 1–3 axially aligned rows of small denticles set back ⅛ to ⅓ whorl behind outer lip, outermost row sometimes visible through aperture, other rows apparent only through translucent shell; each row with up to 5 denticles, with an additional small baso-columellar denticle (easily overlooked); number of denticles and position of rows somewhat variable and related to degree of development; those below periphery more elongate, those above more rounded. Shell translucent, honey-brown when fresh; diameter up to 2.0 mm.

Material examined

Holotype

SOUTH AFRICA • E. Cape, Amatola [Amathole] Mtns, Hogsback; R.F. Lawrence leg.; SAMC MB- A008142.

Paratype

SOUTH AFRICA • 1 specimen; same collection data as for holotype; NHMUK 1937.12.30.2726 .

Other material

SOUTH AFRICA – E. Cape • 14 specimens; Hogsback, environs of Madonna and Child waterfall ; 32.60703° S, 26.96268° E; 1075 m a.s.l.; 25 Jan. 2002; D.G. Herbert, M. Bursey and G. Redman leg.; indigenous forest, under log; NMSA V9795 • 1 specimen; Hogsback, Madonna and Child Falls walk ; 32.60701° S, 26.96257° E; 1075 m a.s.l.; 6 Apr. 2014; D.G. Herbert, L.S. Davis and M. Cole leg.; station 14-02, southern mistbelt forest, in leaf-litter; NMSA W9740 • 5 specimens; Hogsback, Madonna and Child area ; 32.60611° S, 26.96250° E; 1075 m a.s.l.; 31 Dec. 2008; indigenous forest; M. and K. Cole leg.; NMSA W6658 • 3 specimens; same collection data as preceding; ELM D16119 • 2 specimens; Hogsback Forest Reserve ; 32.60° S, 26.93° E; 1300 m a.s.l.; 19 Feb. 1997; D. Barraclough and S. James leg.; indigenous forest, sorted from dried leaf-litter sample; NMSA V4876 • 1 specimen; Hogsback, Hobbiton Forest ; 32.59658° S, 26.95749° E; 1180 m a.s.l.; 6 Apr. 2014; D.G. Herbert, M. Cole and L.S. Davis leg.; station 14-01, southern mistbelt forest, in leaf-litter; NMSA W9751 • 4 specimens; Hogsback ; 32.58935° S, 26.93563° E; 1220 m a.s.l.; 21 Jan. 2005; A. Moussalli and D. Stuart-Fox leg.; indigenous forest, in leaf-litter; NMSA W2841 • 1 specimen; same collection data as preceding; NMSA W4464 • 6 specimens; Stutterheim, Kologha Forest , waterfall walk from picnic site; 32.53387° S, 27.43083° E; 22 Dec. 2009; M. Cole leg.; ELM D16196 • 5 specimens; Stutterheim, Kologha Forest, forest drive near Protea Hill ; 32.5558° S, 27.3175° E; 26 Jan. 2009; M. Cole leg.; ELM D16161 .

Distribution and conservation

A narrow-range endemic ( Fig. 9 ), known only from the Hogsback to Stutterheim area in the Amathole Mountains, E. Cape, at 1075–1300 m a.s.l.; in leaf-litter of southern mistbelt forest. Both the Hogsback and Kologha forests are formally protected areas.

Remarks

Resembles its congener Amatholedonta fordycei gen. et sp. nov.; however, in the latter the axial sculpture is finer and there are only three denticles in each of the rows of palatal teeth. Biomphalodonta forticostata gen. et sp. nov. has a similarly shaped shell, but the axial sculpture is much coarser, the rows of palatal denticles are more distinctly C-shaped and the minute denticle at the junction of the basal and columellar lips is lacking. In addition, the protoconch of B. forticostata gen. et sp. nov. has distinct axial sculpture.

Whereas Connolly (1939) cited six palatal denticles per row in Am. bimunita gen. et comb. nov., Solem (1970) cited only five. This discrepancy indicates either that Solem overlooked the minute basocolumellar denticle or that the NHMUK specimen he examined had fewer denticles than the holotype described by Connolly (this is sometimes the case). Since Solem described the lowest denticle as being the most posterior and the middle two the most anterior, this would suggest that he overlooked the basocolumellar denticle, which is slightly anterior to the lowest palatal denticle.

Figures

Fig. 8. Shells of Amatholedonta gen. nov. and Biomphalodonta gen. nov. species. A–D. Amatholedonta bimunita (Connolly, 1939) gen. et comb. nov., Hogsback, E. Cape, diameter 2.0 mm (NMSA W6658). E–H. Am. fordycei gen. et sp. nov., holotype, diameter 1.84 mm (NMSA W6668/T4270). I–L. Biomphalodonta forticostata gen. et sp. nov., holotype, diameter 2.13 mm (NMSA V6949/T4261). M–O. B. forticostata gen. et sp. nov., paratype, large specimen, diameter 2.7 mm (NMSA V4886/T4262).

Fig. 9. Distribution of Amatholedonta bimunita (Connolly, 1939) gen. et comb. nov. (green circles), Am. fordycei gen. et sp. nov. (blue circles) and Biomphalodonta forticostata gen. et sp. nov. (orange squares). Contour at 1000 m.