Trilobatus sicanus ( de Stefani, 1952 )

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 34-35

Trilobatus sicanus ( de Stefani, 1952)

Pl. 8, fig. 4

Globigerinoides conglobata Cushman & Stainforth, 1945 , pl. 13, fig. 6. (Not Gs. conglobatus ).

Globigerinoides sicana de Stefani, 1952, p.9 .

Praeorbulina sicana Bolli et al., 1985, p. 199 , fig. 24.7; Kender et al., 2008, p. 522, pl. 27, fig. 6.

Description: The test surface is macroperforate and cancellate. The test is globular and circular in cross section. The chambers are rounded, with slit-like apertures separating the chambers. Approximately half of the test is enveloped by the final chamber. The primary aperture appears as a narrow slit-like opening and supplementary apertures form along sutures on the spiral side of the test.

Remarks: The relative abundances of G. bisphericus is trace (<1%) in samples of all three cores. The tests are small, measuring 0.3 mm in diameter.

The likely ancestor of T. sicanus is T. bisphericus ( Spezzaferri et al., 2015) . This species differs from its ancestor in its more enveloping final chamber, with more of the umbilicus being covered. Trilobatus sicanus is also considered to be intermediate between T. bisphericus and Praeorbulina curva ( Bolli et al., 1985) .

Environmental preferences: T. sicanus is identified as a subtropical to tropical species ( BouDagher-Fadel, 2015).

Global stratigraphic range: This species is an indicator species for the Miocene – Burdigalian to Langhian ( Wade et al., 2011; BouDagher-Fadel, 2015).

Regional occurrence: T. sicanus has been identified in Miocene strata from the Congo Basin ( Kender et al., 2008) to the northern Namibian outer continental shelf, south of the Kunene River mouth (this study).