Lenticulina calcar

Lenticulina calcar (Linnaeus, 1758) Pl. 2, figs. 4-5

Nautilus calcar Linnaeus, 1758, p. 709, pl. 14, fig. 14; Linnaeus, 1767, p. 1162, 272.

Lenticulina calcar De Blainville, 1825, p. 390; Barker, 1960, p. 146, pl. 70, figs. 9–12; LeRoy & Levinson, 1974, p. 7, pl. 3, fig. 12; Martin, 1981, p. 32, pl. 8, fig. 6; Kohl, 1985, p. 47, pl. 10, figs. 4–5; Papp & Schmid, 1985, pl. 30, figs. 1–3; Lowry, 1987, p. 165, pl. 9, fig. 4; Bolli et al., 1994, p. 294, pl. 294, pl. 77, fig. 5; Kender et al., 2008, p. 510, pl. 14, fig. 14.

Robulina calcar d’Orbigny, 1846, p. 99, pl. 4, figs. 18–20; Renz, 1948, pl. 3, fig. 6.

Cristellaria calcar Parker et al., 1871, p. 241, pl. 10, figs. 91–94; Brady, 1884, p. 551, pl. 7, figs. 9–12; Nuttall, 1928, pl. 5, fig. 8; Macfayden, 1930, pl. 3, fig. 17.

Robulus calcar Cushman, 1923b, p. 115, pl. 30, fig. 7, pl. 31, figs. 4–5; Bandy, 1956, p. 197, pl. 30, fig. 11; Braga, 1960, p. 101, pl. 10, fig. 4.

Description: The test wall is smooth and calcareous. The large test is involute, planispiral, biconvex with a keeled periphery. Tests have three to four spines extending from alternating chambers. There are up to seven limbate chambers visible in the final whorl, increasing gradually in size toward the apertural end. The sutures are slightly curved. The aperture is terminal and radiate.

Remarks: Lenticulina calcar generally occurs in low relative abundances (<1%) in this study. LeRoy & Levinson (1974) reported a maximum diameter of 0.85 mm. Tests in this study are slightly larger with diameters of up to 1 mm.

This species is distinguished from the other Lenticulina spp. through its spines that extend from the keeled margin of the test. The sutures of this species is also more raised compared to others in this genus.

Life strategy: This species is recorded to live unattached, epifaunal (Corliss and Chen, 1988) and under oxic (Pezelj et al., 2013 and references therein) to suboxic conditions (Kaiho, 1994), preferring muddy substrates (Murray, 1991) on the shelf to middle slope (Gallagher et al., 2001).

Global stratigraphic range: Lenticulina calcar is documented as an extant species, occurring in Miocene to Recent strata (Jones, 1994).

Regional occurrence: The distribution of L. calcar is widespread chronostratigraphically in late Cenozoic strata and spatially along the margin of southern Africa. This species occurs in Miocene strata in the Congo Basin (Kender et al., 2008) to south of the Kunene River mouth (this study). Wefer et al. (1998) do not distinguish between the different species, but recorded minor relative abundances for Lenticulina spp. of less than 5% along the Namibian slope from the late Miocene to Pleistocene. The occurrence of Lenticulina calcar has also been recorded along the entire coastline of South Africa in surface sediments (Martin, 1981; Lowry, 1987).