Bolivina alata ( Seguenza, 1862 )

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 21

Bolivina alata ( Seguenza, 1862)

Pl. 4, fig. 7

Vulvulina alata Seguenza, 1862, p. 115 , pl. 2, fig. 5.

Bolivina alata Cushman, 1937, p. 106 , pl. 13, figs. 3–11; Cushman & Todd, 1945, p. 42, pl. 6, fig. 25; Renz, 1948, p. 116, pl. 6, fig. 26; pl. 12, fig. 12; Lowry, 1987, p. 280, pl. 18, figs. 3a–b; Bolli et al., 1994, p. 339, figs. 78.4–78.5.

Brizalina alata van Marle, 1991, p. 166 , pl. 17, figs. 1–2; Jones, 1994, p. 58, pl. 53, figs. 2–4; Yassini & Jones, 1995, p. 131, figs. 516–517; Robertson, 1998, p. 120, pl. 47, figs. 1–2; Holbourn et al., 2013, p. 76.

Description: The test wall is calcareous and coarsely perforate. The test is small, elongate, biserial, strongly compressed and elliptical in cross-section. The chambers increase rapidly and become more inflated towards the apertural end, slightly overlapping the previous chambers. Chambers have a downward pointing spine located at the base, giving a serrated edge to the test margin. A peripheral keel surrounds the test. The sutures are slightly depressed and curved. The aperture is loop-shaped and extends up the terminal chamber.

Remarks: Specimens were moderately abundant (<10%) in all cores discussed in this study. The tests are small, measuring 0.2 mm in width and 0.6 mm in length.

Life strategy: The genus Bolivina is infaunal, unattached and prefers muddy sediments in dysoxic conditions ( Kaminski et al., 2002). The species Bolivina alata has a shelf distribution ( Holbourn et al., 2013).

Global stratigraphic range: This species occurs from the Miocene to Recent ( Jones, 1994).

Regional occurrence: Bolivina alata is recorded in middle Miocene sediments on the Namibian outer continental shelf, south of the Kunene River mouth (this study) and in surface sediments on the southwestern continental shelf of Africa, north of the Orange River mouth ( Lowry, 1987).