Plectofrondicularia sp. B

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 13

Plectofrondicularia sp. B

Pl. 2, figs. 1–2

Description: The test wall is calcareous. The test is flat with a keeled periphery and biserial in the early stage, becoming uniserial as chambers are added. The later chambers are chevron-shaped. The side abruptly widens and curves where it narrows towards the apertural end. The initial stage protrudes more than the later stage chambers. The sutures are limbate and the aperture terminal, radial with projecting laminae fusing centrally.

Remarks: The tests are large in size (up to 1 mm in width and 3 mm in length), in trace abundances (<1%) in all three cores.

The tests range between narrow (pl. 2, fig. 1) and broad (pl. 2, fig. 2). The tests are mostly broken and resemble Frondicularia sagittula in Jones (1994; pl. 65, fig. 23) and Plectofrondicularia vaughani in Holbourn et al. (2013, p. 422), but with a peripheral keel and the absence of a basal spine. In this study, the specimens have been classified as Plectofrondicularia based on the presence of a keeled margin ( Loeblich & Tappan, 1988). The specimens in this study were not assigned to P. vaughani , because of its broader peripheral keel and thicker, more pronounced proloculus.

Life strategy: Plectofrondicularia spp. have been documented to occur as infaunal and under suboxic conditions ( Pezelj et al., 2013 and references therein).

Regional occurrence: This species occurs in middle Miocene sediments from the northern Namibian outer continental shelf, south of the Kunene River mouth (this study). Wefer et al. (1998) recorded minor occurrences of Plectofrondicularia spp. ( Plectofrondicularia cf. inaequalis , Plectofrondicularia cf. raricosta and Plectofrondicularia cf. semicosta ) in late Miocene to Pleistocene-aged sediments along the Namibian and southwestern South African slope. The highest abundances (<10%) were recorded along the northern Namibian slope ( Wefer et al., 1998).