Praeorbitolina cormyi Schroeder, 1964

SCHLAGINTWEIT, FELIX, 2021, Orbitolinids And Other Larger Benthic Foraminifera From The Aptian-Albian Of Tibet: Critical Discussion Of Some Recently Published Data, Acta Palaeontologica Romaniae 18 (1), pp. 17-23 : 18

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.

Figures

Fig. 2. A-B, Praeorbitolina cormyi Schroeder fide BouDagher-Fadel et al. (2017, fig. 9.6 and 9.5), Lower Cretaceous of Tibet. C-D, Paleodictoyconus actinostoma Arnaud-Vanneau & Schroeder, early Aptian of Central Iran. E, Praeorbitolina cf. wienandsi Schroeder fide BouDagher-Fadel et al. (2107, fig. 12.1). F-G, juvenile specimens of Paleodictyoconus sp., (?P. actinostoma Arnaud-Vanneau & Schroeder), early Aptian of Central Iran. H, Pseudochoffatella cuvillieri Deloffre fide Bou- Dagher-Fadel et al. (2017, fig. 12.7). I-K, unknown lituolid, early Aptian Taft Formation of Central Iran. Figures without scale.