Globigerina bulloides d'Orbigny 1826

Globigerina bulloides d’Orbigny, 1826 Pl. 7, figs. 5–6

Globigerina bulloides d’Orbigny, 1826, p. 277; Lowry, 1987, p. 354, pl. 24, figs. 1a–c; Banner & Blow, 1960, p. 3, pl. 1, figs. 1a–c; Bé & Hamlin, 1967, p. 98, fig. 8; Hayward, 1983, p. 64, figs. 2C–E; Bolli et al., 1985, p. 321, figs. 4.1–2; Spezzaferri et al., 2018a, p. 183, pl. 6.2, figs.1–16.

Description: The test wall is calcareous and macroperforate, with the test being covered with short bases from which spines of the living form would extend between pores. The chambers are globular in shape and trochospirally arranged. There are four spherical enlarging chambers in the final whorl, with the terminal chamber being the largest. The sutures between chambers on all sides are depressed. One large aperture is formed in an asymmetric arch in the final chamber and is umbilically positioned.

Remarks: This species is a major component (<80% of the planktic assemblage) in samples of all three cores. The tests are up to 0.5 mm in diameter.

This species might be confused with those of Globigerinella when viewed from the umbilical angle, but there are differences among the various species. Globigerina bulloides is different from its Globigerinella counterparts by the location of its aperture, trochospire and pore density. In G. bulloides, the large aperture is located more centrally or umbilical, compared to Globigerinella obesa and Globigerinella siphonifera. The trochospire in Globigerinella spp. is also lower compared to G. bulloides. This species also has a higher pore density and the final chamber is less inflated compared to that of Globigerinella. The terminal chamber is also closer in size to the preceding chambers, whereas the chambers increase in size more rapidly in G. obesa. G. bulloides also has one less chamber in the final whorl compared to Globigerinella praesiphonifera. G. bulloides and Globigerinella, however, form different phylogenetic lineages (Spezzaferri et al., 2018a).

Environmental preferences: G. bulloides is a good indicator of upwelling conditions, particularly along the fringes of upwelling centers (Giraudeau, 1993). This species also occurs in transitional to temperate ocean waters (Kucera, 2007).

Global stratigraphic range: This species has a long stratigraphic time range, having been documented to occur from the upper Oligocene to Recent (Kennett & Srinivasan, 1983; Bolli et al., 1985).

Regional occurrence: This is an abundant species ranging from the Neogene to Quaternary along the continental margin of northern Namibia (this study) and South Africa (Lowry, 1987; Giraudeau, 1993; Wefer et al., 1998; Rau, 2002; Rau et al., 2002).