Amphicoryna scalaris (Batsch, 1791)

Pl. 3, figs. 5a–b

Nautilus (Ortoceras) scalaris Batsch, 1791, p. 2, pl. 2, figs. 4a–b.

Nodosaria scalaris Brady, 1884, p. 510, pl. 63, figs. 28–31.

Amphycorine falx Brady, 1884, p. 556, pl. 65, figs. 7–9.

Amphicoryna scalaris Loeblich and Tappan, 1988, p. 410, pl. 450, figs. 11–15; Jones, 1994, p. 77, pl. 65, figs. 7–9; Yassini & Jones, 1995, p. 136, fig. 724; Murray, 2003, p. 17, fig. 5.1; Milker and Schmiedl, 2012, p. 73, fig. 18.22–25.

Description: The test wall is calcareous and the surface covered with ridges running along most of the length of the chambers. The test is elongate and uniserial, circular in cross-section, with several inflated globular chambers, separated by deeply incised sutures. A maximum of approximately twenty ridges run along the terminal chamber. The ridges increase in number towards the terminal chamber and do not extend the full length of the chambers. The aperture is terminal at the end of a neck.

Remarks: Specimens are small to moderate in size, with the larger terminal chamber reaching ~ 0.15 mm and the test 0.6 mm in length. The relative abundance is generally low, forming minor components in some of the core samples.

Life strategy: The bathymetric range of Amphicoryna spp. is broad, from the shelf to abyssal depths. The preferred substrate is mud, under low oxygen (suboxic) (Rögl & Spezzaferri, 2002; Kaminski, 2012) to high oxygen conditions (Milker & Schmiedl, 2012).

Regional occurrence: Amphicoryna scalaris occurs in middle Miocene sediments on the Namibian outer continental shelf, south of the Kunene River mouth (this study).