Amphistegina d’Orbigny 1826

Schönfeld, Joachim & Lübbers, Julia, 2020, Checklist, assemblage composition, and biogeographic assessment of Recent benthic foraminifera (Protista, Rhizaria) from São Vincente, Cape Verdes, Zootaxa 4731 (2), pp. 151-192 : 163

Genus Amphistegina d’Orbigny 1826

Amphistegina gibbosa d’Orbigny 1839b, p. 120 , pl. 8, figs. 1–3 [Plate 4, Figs. 15–17, Plate 5, Figs. 1 –3]. Crouch & Poag (1979), p. 91, pl. 1, figs 5, 8. Eichler et al. (2019), fig. 1. ” Amphistegina lessonii ” Bock (1971) , p. 58, pl. 21, fig. 10. Note: Amphistegina lessonii d’Orbigny 1826 occurs in the Pacific, and the slightly more compressed Amphistegina gibbosa d’Orbigny 1839b is confined to the Atlantic ( Larsen 1977). Amphistegina lessonii is sinistrally coiled and shows 8 chambers per whorl, while Amphistegina gibbosa is dextrally coiled and has on average 15 chambers per whorl ( Crouch & Poag 1979). In fact, 17 of 26 well preserved Amphistegina specimens of the dead assemblage from Sao Pedro are dextrally coiled and show 12 to 14 chambers. The Cape Verdean specimes show a high variability from plano-convex to biconvex shape, as it has been observed off Brazil ( Eichler et al. 2019). The thickness of most tests resembles the High Light morphotype of Hallock et al. (1986, there Figure 4).

Figures

FIGURE 1. Map with location of (a) the Cape Verde Archipelago and (b) sampling sites on São Vincente. CC: Canary Current, CUC: Canary Upwelling Current, CVC: Cape Verde Current, CVFZ: Cape Verde Frontal Zone, GD: Guinea Dome, NEC: North Equatorial Current, NECC: North Equatorial Counter Current (modified after Fiedler, 2012; Fernandes et al. 2015; Pelegrí & Peña-Izquierdo, 2015). Depth contours in (a) were given for the continental margin only. Colours and symbols in (b): light grey: volcanic or volcanoclastic rocks, yellow: sedimentary deposits (redrawn after Ancochea et al. 2010), orange: beach sands, dark grey and circles: urban areas and villages (after satellite images and observations during the geological excursion), arrows: sampling sites. The geographical coordinates are given in Appendix Table 1.