Lenticulina iota ( Cushman, 1923a ), Barker, 1960

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 15

Lenticulina iota ( Cushman, 1923a)

Pl. 2, figs. 9a–b

Cristellaria cultrata Brady, 1884, p. 550 , pl. 70, fig. 4–6.

Cristellaria iota Cushman, 1923a , p. 111, pl. 29, fig. 2; pl. 30, fig. 1.

Lenticulina iota Barker, 1960 , pl. 70, fig. 4–6; Thomas, 1988, p. 74, pl. 1, fig. 10; Jones, 1994, p. 81, pl. 70, fig. 4–6; Holbourn et al., 2013, p. 336.

Description: The test wall is calcareous, smooth and finely perforate. The test is planispiral, involute and biconvex in side view. A keel surrounds the test margin. The keel is initially broad, narrowing towards the terminal end. The chambers gradually increase in size. The sutures are flush and curved. The aperture is radiate and terminal.

Remarks: Specimens are relatively large, measuring up to 1 mm in diameter.The relative abundance is generally low, forming minor components (<1%) in some of the core samples.

Similar to most other species in this genus, L. iota is rounded, but is distinguished from the other Lenticulina spp. by its broad and thin, near transparent or translucent keel around the margin of the test. The umbilical pillar is also thicker and more pronounced, compared to other species, e.g., L. cultrata .

Life strategy: Species of the genus Lenticulina are generally epifaunal ( Corliss and Chen, 1988) under oxic ( Pezelj et al., 2013 and references therein) to suboxic conditions ( Kaiho, 1994). The bathymetric range of Lenticulina iota is given as shelf to upper slope ( Holbourn et al., 2013).

Global stratigraphic range: This species is extant and occurs from the Miocene to Recent ( Thomas, 1988).

Regional occurrence: This study documents L. iota to occur in middle Miocene sediments on the outer Namibian continental shelf, south of the Kunene River mouth (this study). Lowry (1987) recorded this species from the continental shelf in surface sediments off Cape Agulhas, South Africa.