Palorbitolina lenticularis (Blumenbach, 1805)

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 : 19

Extension of Palorbitolina lenticularis into the latest late Aptian

An axial section of P. lenticularis with well developed peri-embryonic ring has been illustrated by BouDagher-Fadel et al. (2017) in fig. 9.1 therein from the upper lower Aptian. The specimen on the basis of which the extension into the latest Aptian and the resulting overlapping range with Mesorbitolina texana (see range chart, fig. 13 therein) has not been illustrated. In the orbitolinid biostratigraphic chart of Schroeder et al. (2010, Fig. 3) P. lenticularis has its LAD at the early-late Aptian (= Bedoulian-Gargasian boundary) while M. texana has its FAD in the late Gargasian. In the absence of illustration and reproducible data such as those of Granier et al. (2013, 2017) extending the FAD of P. lenticularis into the late early Barremian, the occurrence of Palorbitolina in the upper Aptian in Tibet is doubted herein. During the early Aptian the peri-embryonic ring of Palorbitolina lenticularis shifted more and more towards the base of the proloculus (> Palorbitolina ultima ) giving rise to the genus Palorbitolinoides with a subembryonic zone completely enveloping the former in the late early Aptian ( Cherchi & Schroeder, 1980; Schroeder et al., 2010). An occurrence of Palorbitolina in the late Aptian would counteract the phylogenetic lineages (see Schroeder et al., 2010, fig. 3).