Praeorbitolina, 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 : 18-19

Extension of Praeorbitolina to the top of the Albian

( Fig 2E )

Referred illustration: Praeorbitolina cf. wienandsi , figure 12.1 in BouDagher-Fadel et al. (2017).

The comparably short range of Praeorbitolina in the upper lower Aptian (upper Bedoulian) has been recorded from all over the Tethysian realm since the description of the species in the sixties (e.g., Schroeder, 1964; Moullade et al. 1985; Cherchi et al., 1999; Schroeder et al., 2010; Schlagintweit et al., 2013). Its stratigraphic distribution has been questioned by BouDagher-Fadel et al. (2017) extending its range to the top of the Albian in the “Tibetian Platform”. This assumption is based on an axial section of an orbitolinid showing the megalospheric embryo at the beginning of a small eccentric spire. It shows a spherical embryo and one smaller chamber (deuteroconch or first post-embryonic chamber) partly enclosing the former; a subembryonic zone as typical for the genus is lacking. Comparable sections from the lower Aptian of Iran refer to juvenile specimens of Paleodictyoconus sp. (probably P. actinostoma ) ( Fig. 2 F-G). Thus, there is in my opinion no evidence that Praeorbitolina extends to the top of the Albian, thereby reinstating the lineage Praeorbitolina (late early Aptian)- Mesorbitolina (late Aptian-Albian) (e.g., Schroeder et al., 2010). Only recently the extension of Praeorbitolina into the top of the Aptian has been proposed (Gheiasvand et al., 2020) based on incorrect species identification of associated taxa (see Schlagintweit, 2022 for details). Last but not least, mention should be made that the presence of Paleodictyoconus actinostoma in Tibet fits with the northern Neotethysian orbitolinid assemblages. From the former southern margin of the Neotethys, P. actinostoma has far not been recorded.

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.