Sphaeroidina bulloides d’Orbigny, 1826

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 25

Sphaeroidina bulloides d’Orbigny in Deshayes 1828

Pl. 5, figs. 3a–b

Sphaeroidina bulloides d’Orbigny, 1826, p. 267 ; LeRoy & Levinson, 1974, p. 8, pl. 5, fig. 2; Martin, 1981, p. 36, pl. 10, fig. 5; Papp & Schmid, 1985, p. 96, pl. 90, figs. 7–12; Lowry, 1987, p. 379, pl. 27, figs. 7a–c; Jones, 1994, p. 91, pl. 84, figs. 1–2; Yassini & Jones, 1995, p. 160, figs. 936–937; Robertson, 1998, p. 196, pl. 74, fig. 4; Kender et al., 2008, p. 516, pl. 20, fig. 3; Holbourn et al., 2013, p. 520.

Sphaeroidina austriaca d’Orbigny, 1846, p. 284 , pl. 20, figs. 19–21.

Description: The test wall is calcareous, imperforate and its surface is smooth. The test is subglobular, with globular chambers separated by slightly depressed sutures. The last whorl contains three chambers. The aperture is located near the junction between three chambers and is crescentic in shape, with a bordering lip (pl. 5, fig. 3b).

Remarks: The relative abundances of Sphaeroidina bulloides in this study decrease toward the deeper cores. In core 2658, S. bulloides formed one of the major species in some of the samples (<20%), and in cores 2670 and 2682, minor (<5%).

The test sizes of Sphaeroidina bulloides in general are variable. Diameters in LeRoy & Levinson (1974) range between 0.23 and 1.15 mm. The diameter measured for specimens in this study is ~ 0.5 mm.

Life strategy: This species is infaunal under suboxic ( Kaiho, 1994) to dysoxic conditions ( Pezelj et al., 2013 and references therein). Its bathymetric distribution stretches from the slope to abyssal depths ( Holbourn et al., 2013).

Global stratigraphic range: Sphaeroidina bulloides occurs from the Oligocene to Recent ( Jones, 1994; Holbourn et al., 2013).

Regional occurrence: This species occurs in Miocene-aged strata, stretching from the Congo Basin ( Kender et al., 2008) to the outer continental shelf of Namibia, south of the Kunene River mouth (this study) and the southwestern shelf of South Africa ( Compton et al., 2004). Hay et al. (1984) reported the occurrence of Sphaeroidina bulloides in late Miocene to Pleistocene sediments on the slope off the Walvis Ridge. Low relative abundances (<1%) of this species occur along the slope of Namibia during the late Miocene , with higher abundances off the Orange River to the south (<15%). Wefer et al. (1998) recorded high relative abundances of this species (<80%) along the slope off the Walvis Ridge during the Pliocene, decreasing in abundance towards the south. Low relative abundances (<1%) of this species have been recorded to occur along the Namibian slope and minor abundances (<10%) along the southwestern slope of South Africa during the Pleistocene ( Wefer et al., 1998). Lowry (1987) documented Sphaeroidina bulloides in surface sediments on the continental shelf between Lüderitz, Namibia and Cape Agulhas, South Africa.