Palorbitolinoides hedini Cherchi & Schroeder, 1980

SCHLAGINTWEIT, FELIX, 2023, Annular Chambers In Cretaceous Orbitolinidae (Larger Benthic Foraminifera): An Overview, Acta Palaeontologica Romaniae 19 (1), pp. 45-52 : 46-47

Palorbitolinoides hedini Cherchi & Schroeder, 1980

Fig. 2 a-d

*1980 Palorbitolinoides hedini n. gen., n. sp. – Cherchi & Schroeder, p. 385, pl. 1, figs. 1-5.

Remarks: The following statements refer to the type-species Palorbitolinoides hedini Cherchi & Schroeder, 1980 , first described from lower Albian strata of Tibet, but known to range younger ( Schlagintweit et al., 2022). The genus is defined exclusively on the structure of the megalospheric embryo ( Cherchi & Schroeder, 1980). As in other orbitolinids, gross external test morphology is variable in P. hedini and is therefore not of taxonomic significance ( Figure 2 ). The specimens studied herein are from distinctive beds of the middle Albian Kazhdumi Formation of southwestern Iran (Zagros Zone) ( Schlagintweit et al., 2022). Morphologically, they are mostly low-conical to almost discoidal, corresponding to the convexo-concave and conico-concave types with or without reflexed chamber margins ( Henson, 1948, fig. 12). In some specimens, the large-sized apical embryo is followed by a few uniserial chambers with distinct convex apertural faces due to the embracement of the embryo ( Figure 2a, d ). The rest of the test consists of annular chambers (compare Fig. 1j ). However, there are also specimens where the embryo is immediately followed by annular chambers ( Figure 2b–c ). In these mostly flat discoidal specimens, the base of the embryo corresponds to the base of the test. The test of the holotype specimen of P. hedini shown in pl. 1, fig. 5 of Cherchi & Schroeder (1980) is comparably thick (about 2.5 times the height of the embryo) with numerous chambers with convex apertural faces in most chambers. In the latest part, the chambers are sigmoseptal ( Figure 1e ), and the presence of any annular chambers is not discernible and unclear.

Figures

Fig. 2 Annular chambers in Palorbitolinoides hedini Cherchi & Schroeder from the middle Albian Kazhdumi Formation of southwestern Iran. a Reflexed conico-concave test (Henson, 1948, fig. 12k–l). Early uniserial post-embryonic chambers marked in orange. b–c Low conico-concave test (Henson, 1948, fig. 12i–j) completely formed by annular post-embryonic chambers, so that the embryo base marks the test base. d High covexo-concave test (Henson, 1948, fig. 12r); compare to the specimen of Pseudorbitolina schroederi Luger shown in Fig. 3d.

Fig. 1 Examples for the terminology of chamber morphology (modified from Rat, 1963). Annular chambers in f-g and j are marked in gray.