Sokolowia Böhm, 1933

Hadi, Mehdi, Salahi, Amir, Nasiri, Yaghub & Mosaddegh, Hossein, 2019, Sokolowia Horizon Of The Ziarat Formation (Eastern Alborz, Iran): Biostratigraphic And Paleogeographic Implications, Acta Palaeontologica Romaniae 15 (2), pp. 15-27 : 18

Genus Sokolowia Böhm, 1933

Type species: Gryphaea buhsii Grewingk, 1853 Sokolowia buhsii, Grewingk, 1853 Figure 3 a-j

* 1853 Grypheae buhsii, Grewingk , p. 210, Fig.-t. 1871 Gryphaea esterhazy, Pavay , p. 375, pl. 8, Fig.2 ; pl. 10, Fig.3 .

1937 Gryphaea esterhazy, Vialov , p. 20, pl. XI

1938 Fatina esterhazy, Vialov , p. 16.

1948 Fatina (Sokolowia) esterhazy, Vialov , p. 73, pl. 2- 32.

1970 Fatina (Sokolowia) esterhazyi esterhazyi, Berizzi Quarto di Palo , p. 188, pl. 29, Figs. 1- 2 , pl. 30, Fig. 1 .

1971 Sokolowia, Stenzel , p. 1147, Figs. J121-J122.

2004 Sokolowia esterhazyi, Rusu et al. , p. 451, pl. 1, Figs. 1-2

2011 Sokolowia buhsii - Salahi & Vahidinia, p. 56, pl. 1, Fig. 4

2014 Sokolowia buhsii - Bosboom et al., p. 110, Fig. 6 . 9.

2016 Sokolowia buhsii - Bougeois et al., p. 613, Fig. 1 . iii.

Material: eighteen left valves, twelve right valves, MASSH 0001 - MASSH 0030 .

Stratigraphic occurrence in the Alborz Basin : Ziarat Formation , Kalateh Section : Horizon 1 at 26.5 m from the base; horizon 2 at 27.5 m from the base; horizon 3 at 29m from the base. Dimensions; (left valve): length (L) 54 mm, height (H) 79 mm, shell thickness 46 mm, (right valve): length (L) 32 mm, height (H) 43 mm, shell thickness 11 mm .

Description: Our Sokolowia specimens are characterized by well-preserved, medium to large sized, inflated, subequilateral, thick walled shells, homeomorphous with Gryphaea (gryph shaped). The left valve is strongly convex with a narrow, high and recurved umbo. The ligament area is oblique, the interior shell surface smooth. In the ovoid internal cavity the reniform and semicircular muscle scar is placed near its center. The right valve is inequilateral, flattened, concave and triangular in outline, without ribs, but with fine concentric growth lines. The left valve is covered partially or fully with weak to strong radial ribs; they are slender and densely spaced. In the umbonal region, they are a lot and in short distance, but almost disappear toward ventral margin part and only concentric lamellae can be visible.

Remarks: Ornamentations of the Sokolowia buhsii morph. Buhsii is present in the left valve from the umbonal region up to the ventral margin, whilst in the Sokolowia buhsii morph. Esterhazyi they are limited to the umbonal region, almost disappearing toward the ventral margin where concentric lamellae become prominent ( Fig. 3 ). Note, that also Stenzel (1971) considered latter differences as morphological variation of the same species.

Figures

Fig. 3 a-f Sokolowia buhsii morph. Buhsii; g-j Sokolowiabuhsii morph. esterhazyi from Kalateh section (Eastern Alborz region).

Fig. 2 Stratigraphic distribution of larger foraminiferal species and other fossil groups in the Kalateh section, eastern Alborz zone. Modified after Hadi et al. (2019)

Fig. 1 a Tethys mountain ranges (simplified from Okay, 1989 and Özcan et al., 2015) and location of studied region in eastern Alborz zone. b Modified sketch map of Iran showing geologic provinces (adapted from Stöcklin, 1968 and Aghanabati, 2004). c Simplified geological map from eastern Alborz region (after General geological map of Iran, 1:250000 from Sharabi, 1990). Modified after Hadi et al. (2019).

Fig. 4 Biostratigraphically significant larger foraminifera taxa: a-e Equatorial and axial sections of both megalospheric and microspheric form Nummulites lyelli (D'Archiac & Haime). a-b microspheric form, equatorial section, sample N59- N60, c microspheric form, axial section, sample N61, d megalospheric form, equatorial section, sample N55, e external view, f-g Equatorial sections of megalospheric form Orbitoclypeus zitteli (Checchia-Rispoli), sample O25 & O45, h-i Equatorial sections of megalospheric form Asterocyclina stella stella (Gümbel), sample O32. Modified after Hadi et al. (2019).

Fig. 6 a Outcrop view of the Khangiran Formation and Neogene red beds in the Yaghol section (Kopet-Dagh region). b Panoramic view of the Ziarat Formation, Karaj Formation and Neogene red beds in the Kalateh section (Alborz region). c Close-up view of the Nummulites tests in the Kalateh section. d-e Sokolowia samples of the calcareous marl deposits in the Kalateh section.