Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf
Author
Bergh, Eugene W.
0000-0002-0765-4141
Marine Research Institute and Department of Geological Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa. & Department of Environmental and Geographical Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa; & Invertebrate palaeontology and Geology, Iziko South African Museum, P. O. Box 61, Cape Town 8000, South Africa. john. compton @ uct. ac. za; https: // orcid. org / 0000 - 0002 - 0765 - 4141
john.compton@uct.ac.za
Author
Compton, John S.
Marine Research Institute and Department of Geological Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa.
text
Zootaxa
2022
2022-01-12
5091
1
1
55
journal article
2636
10.11646/zootaxa.5091.1.1
51b42715-ddb1-4b4a-aad4-8be0f600a287
1175-5326
5840434
ABC8AF70-F691-4D07-8F20-70934642C8BC
Globigerinella obesa
(Bolli, 1957)
Pl. 7, figs. 9–10
Globorotalia obesa
Bolli, 1957, p. 119
, pl. 29, figs 2–3.
Globigerina praebulloides
Blow, 1959
, pl. 8, fig. 47;
Kender, 2007
, p. 202
, pl. 49, fig. 7.
Globigerinella obesa
Bolli
et al.
, 1985
, p. 206
, fig. 26.44;
Kennett & Srinivasan, 1983
, p. 234
, pl. 59, figs 2–5;
Kender
et al
., 2008
, p. 202
, pl. 29, fig. 4;
Spezzaferri et al., 2018a
, p. 198
, pl. 6.1, figs. 14–17; pl. 6.8, figs. 1–23.
Description
: The wall surface is cancellate-spinose. The test is trochospirally arranged with the chambers globular in shape, which rapidly enlarge towards the terminal end. Four chambers are visible in the final whorl in umbilical view, with straight depressed sutures. The test is biconvex in marginal view and has a lobate outline in umbilical view.A thin imperforate lip may border the apertural arch. The aperture extends from the umbilical to extra-umbilical region, forming an arched shape visible in the peripheral margin view.
Remarks:
The relative abundance of
G. obesa
in this study is trace (<1%) in samples of all three cores. The tests are relatively moderate in size, measuring up to
0.5 mm
in diameter.
G. obesa
is ancestral to
Globigerinella siphonifera
, which later gave rise to
Globigerinella calida
. This species evolved from
G. archaeobulloides
and is different from that species in its aperture, which is more umbilical to extraumbilical towards the margin of the test. It also differs from
G. bulloides
in this way and has a more inflated terminal chamber compared to its initial chambers.
G. obesa
is different from
G. praesiphonifera
in having four chambers in the last whorl, whereas
G. praesiphonifera
has five (
Spezzaferri
et al
., 2018a
).
Globigerina praebulloides
is synonymised and now accepted as
G. obesa
.
Environmental preferences:
G. obesa
has been identified as a warm to temperate species (
Bicchi
et al
., 2003
).
Global stratigraphic range:
G. obesa
has been recorded in Oligocene to lower Pliocene strata (
Kennett & Srinivasan, 1983
).
Regional occurrence:
This species has been recorded to occur in middle 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).