Orbitolinids And Other Larger Benthic Foraminifera From The Aptian-Albian Of Tibet: Critical Discussion Of Some Recently Published Data
Author
SCHLAGINTWEIT, FELIX
Lerchenauerstr. 167, 80935 Munich, Germany
felix.schlagintweit@gmx.de
text
Acta Palaeontologica Romaniae
2021
2021-09-09
18
1
17
23
http://dx.doi.org/10.35463/j.apr.2022.01.03
journal article
10.35463/j.apr.2022.01.03
1842-371x
10520845
Record of
Praeorbitolina cormyi
Schroeder, 1964
and
Praeorbitolina wienandsi
Schroeder, 1964
(
Fig. 2
A-B, E)
Referred illustrations:
Praeorbitolina cormyi
, figures
9.3 to 9.7 in
BouDagher-Fadel et al. (2017)
.
Praeorbitolina
cf.
wienandsi
, figure
12.1 in
BouDagher-Fadel et al. (2017)
.
The specimens of
P. cormyi
illustrated by
BouDagher-Fadel et al. (2017)
are low-conical with test diameter of up to
2.3 mm
(
Fig. 2
A-B). Although no detail of the embryo is provided, in my opinion, it is well discernible that a subapical simple embryo of one or two chambers (= protoconch and deuteroconch or first postembryonic chamber) that lacks a subembryonic zone is present. Such an embryo
type
is reported from the dictyoconid
Paleodictyoconus actinostoma
Arnaud-Vanneau & Schroeder. Examples
of comparable specimens from the early
Aptian
of
Iran
are shown in
Figure 2
C-D.
The
adult specimens illustrated by
BouDagher-Fadel et al. (2017
, fig. 9.5 and 9.6) show a low conico-concave test morphology (e.g.,
Henson, 1948
, fig. 12i) typical for
P. actinostoma
.
This
morphology results from sigmoseptal (in cases annular) adult chambers leading to a striking central depression at the cone base (
Arnaud-Vanneau & Schroeder, 1976
; Clavel in
Granier et al, 2013
,
2017
).
The
principal occurrence of
Praeorbitolina cormyi
in
lower Aptian
limestones of the
Tibetian area
is well recorded (e.g.,
Zhang, 1991
) but, in my opinion the specimens illustrated by
BouDagher-Fadel et al. (2017)
do not belong to this species.
The
specimen of
Praeorbitolina
cf.
wienandsi
(
BouDagher-Fadel et al., 2017
, fig. 12.1) shows a biloculine embryo (protoconch and deuteroconch) lacking a subembryonic zone in my opinion (
Fig. 2E
).
The
specimen from
Tibet
might belong to
Paleodictyoconus
sp.
(see
Fig. 2
F-G for comparison).
This
conclusion provides a revised basis interpretation for the provided biostratigraphic framework therein.