Cibicidoides crebbsi ( Hedberg, 1937 )

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 26

Cibicidoides crebbsi ( Hedberg, 1937)

Pl. 5, figs. 7a–c

Eponides crebbsi Hedberg, 1937, p. 679 , pl. 92, fig. 1; Bolli et al. 1994, p. 240, pl. 55, figs 16–17, p. 298, pl. 79, fig. 8.

Truncatulina floridana Nuttall, 1928, p. 98 , pl. 7, figs. 14, 16.

Cibicidoides crebbsi van Morkhoven et al., 1986, p. 139 , pl. 45; Katz & Miller, 1993a, pl. 2, fig. 5; Kender et al., 2008, p. 516, pl. 20, figs. 4–5; Holbourn et al., 2013, p. 168 –169.

Description:The test wall is calcareous and macroperforate.The test is slightly inflated, trochospiral and planoconvex to unequally biconvex in side view and in cross-section. Approximately ten chambers are visible in the final whorl. The chambers gradually increase in size toward the terminal apertural end. The chambers are separated by flush, less perforate sutures. The sutures on the spiral side are oblique, whereas sutures on the umbilical side are more radial and irregular. The aperture is an interio-marginal basal slit.

Remarks: The relative abundances for Cibicidoides crebbsi decrease toward deeper depths, forming minor (<10%) components in the samples of all three cores. Tests are relatively moderate to large in size, measuring up to 1 mm in diameter.

Life strategy: Species of the genus Cibicidoides are generally unattached, epifaunal to shallow infaunal under oxic conditions ( Pezelj et al., 2013 and references therein), preferring muddy substrates ( Murray, 1991). The species C. crebbsi has a slope distribution ( Holbourn et al., 2013).

Global stratigraphic range: This species occurs from the early Oligocene to early Pliocene ( Holbourn et al., 2013).

Regional occurrence: Cibicidoides crebbsi is documented to occur in middle Miocene strata on the outer continental shelf of Namibia, south of the Kunene River mouth (this study) and in the Congo Basin ( Kender et al., 2008).