Dicyclina, MUNIER-CHALMAS, 1887

Schlagintweit, Felix & Rashidi, Koorosh, 2018, Suraqalatia Brasieri Görmuş, Lawa & Nuaimy, 2017 (Larger Benthic Foraminifera; Suraqalatiidae N. Fam.) From The Late Maastrichtian Of The Tarbur Formation (Zagros Fold-Thrust-Belt) And Remarks On Dicyclina Munier-Chalmas, 1887, Acta Palaeontologica Romaniae 14 (1), pp. 21-29 : 26

REMARKS ON DICYCLINA MUNIER-CHALMAS, 1887 , FROM THE UPPER CRETACEOUS OF IRAN

The genus Dicyclina Munier-Chalmas (Albian? Cenomanian-Maastrichtian) is represented by three species: the type-species D. schlumbergeri Munier-Chalmas, 1887 (Coniacian-Santonian of S-France), D. simplex Cherchi & Schroeder, 1990a (Middle Cenomanian of France), and D. sampoi Cherchi & Schroeder, 1990b (Cenomanian of Iran). These differ in the complexity of the embryo as an essential criterion, the chamber shape in axial sections, and the wall structure. Concerning the latter aspect, the European taxa ( D. schlumbergeri and D. simplex ) possess an agglutinated-keriothecal wall, lacking in the Middle East D. sampoi . As has been pointed out by Cherchi & Schroeder (1990b, p. 210), however, this might be due to a disappearance by diagenetic processes. The differences of the three species are mainly due to the size, position and complexity of their megalospheric embryonic apparatuses ( Cherchi & Schroeder 1990a, b, for details). For the two species occurring in the Upper Cretaceous of Iran, D. sampoi (Cenomanian of Sarvak Fm.; Fig. 6 ) and D. schlumbergeri (Maastrichtian Tarbur Fm.; Fig. 7 ), the difference mainly refers to the complexity of the embryonic apparatus. D. sampoi exhibits an irregularly ellipsoidal embryo with a complex supra- and subembryonic zone composed of main and intercalary partitions. The diameter of the embryonic apparatus of the specimen (slightly oblique axial section) shown in Figure 6 is 1.5 mm ( Cherchi & Schroeder, 1990b: up to 0.86 mm). The connection between the embryonic and post-embryonic chambers has not been evidenced in the original description. It is represented by pores (foramina) with a diameter of ~ 0.045 mm situated between the supra- and subembryonic zones. The protoconch has a diameter of ~ 1.2 mm and a height of ~ 0.55 mm. Dicyclina sampoi was described by Cherchi & Schroeder (1990b) from the middle-upper Cenomanian Sarvak Formation of the Zagros Range. From this formation it was erroneously reported in recent years as Dicyclina schlumbergeri Munier-Chalmas ( Afghah & Fadaei, 2014; Omvidar et al., 2014;

Figures

Fig. 6 Dicyclina sampoi Cherchi & Schroeder, from the Cenomanian of the Sarvak Formation, Zagros Zone, SW Iran, slightly oblique axial section (from Omidvar et al., 2014, fig. 3.10 as Dicyclina schlumbergeri). Megalospheric specimen showing embryonic apparatus and bilateral symmetric pores (foramina) enabling the communication with the first cyclic postembryonic chamber. These are located between the supra- (upper; in yellow) and subembryonic zones (below; in red) (arrows). Both zones are subdivided by primary (b = beams) and secondary partitions (ib = intercalary beams).

Fig. 7 Dicyclina schlumbergeri Munier-Chalmas, Late Maastrichtian Tarbur Formation of the Naghan section. a–b Oblique equatorial sections showing embryonic chamber, kidney-shaped in outline. Note the presence of primary partitions only (arrows). c Oblique section of a juvenile specimen. d, f Partial, slightly oblique axial sections. e Fragmentary equatorial section. Scale bars = 1 mm. Thin-sections: 2NG 191 (a), NG 83 (b), NG 13-1 (c), NG 34 (d), NG 49 (e), 2NG 34 big (f).