Globorotalia archeomenardii Bolli 1957

Globorotalia archeomenardii Bolli, 1957 Pl. 7, figs. 4a–c

Globorotalia archeomenardii Bolli, 1957, p. 119, pl. 28, fig. 11; Bolli et al., 1985, p. 223, pl. 32, fig. 6; Kender et al., 2008, p. 521.

Description: The wall surface is smooth and macroperforate. The test has a keeled margin, is compressed, unequally biconvex, with up to five crescent-shaped chambers visible on the umbilical side, rapidly increasing toward the apertural end. The chambers increase in size toward the terminal end. Earlier chambers are slightly pustulose on the umbilical side opposite the apertural opening. The sutures are depressed, oblique, radial and slightly curved. The aperture is an extra-umbilical slit.

Remarks: Specimens of G. archeomenardii are not very abundant and only occur as trace in some of the samples. The tests are moderate in size, measuring 0.4 mm in width and 0.65 mm in length.

This species is placed within the Globorotalia menardii group or ‘ Menardella’ lineage and identified as G. archeomenardii based on its keeled margin, chamber arrangement, outline and test structure. G. archeomenardii differs from its descendent G. praemenardii in being smaller and has a more biconvex outline in side view and equatorial section. Its spiral side is also more curved. This species differs from G. menardii in generally being smaller, more lobate and having a less developed or thinner keel (Kennett & Srinivasan, 1983). G. menardii is more rounded in outline and has more chambers in its last whorl, usually up to six or six and a half.

G. archeomenardii is considered to have evolved from Globorotalia praescitula in tropical conditions during the early Miocene (Kennett & Srinivasan, 1983).

Global stratigraphic range: This species has been recorded to occur in the Miocene from the Burdigalian to the Serravalian (Kennett & Srinivasan, 1983; Wade et al., 2011; BouDagher-Fadel, 2015).

Environmental preferences: G. archeomenardii is recorded to occur in subtropical to tropical waters (BouDagher-Fadel, 2015).

Regional occurrence: This species occurs in middle Miocene strata from the Congo Basin (Kender et al., 2008) to the outer continental shelf of Namibia, south of the Kunene River mouth (this study).