Pseudotextulariella brevicamerata, SCHLAGINTWEIT & YAZDI-MOGHADAM, 2023

SCHLAGINTWEIT, FELIX & YAZDI-MOGHADAM, MOHSEN, 2023, Pseudocyclammina Sarvakensis Sp. Nov. And Pseudotextulariella Brevicamerata Sp. Nov.: Further Evidence For The Cenomanian Megadiversity Of Larger Benthic Foraminifera From The Sarvak Formation Of Sw Iran, Acta Palaeontologica Romaniae 19 (2), pp. 3-13 : 7-10

Pseudotextulariella brevicamerata sp. nov.

Fig. 5 a-i, k

Derivatio nominis: Prefix brevis (latin) = short combined with camerata = chamber.

Holotype: Specimen illustrated in Figure 5e , oblique axial section, sample RAP 188 .

Type-locality: Tang-e Darbast section, Interior Fars, Zagros Mountains ( Figs. 2-3 ) .

Type-horizon: Lower part of the middle Cenomanian of the Sarvak Formation.

Description: Conical to wedge-shaped test, slightly compressed, higher than wide and with a central depression at the base. The test exhibits a well developed biserial part with chambers of distinctly reduced height compared for example with the test diameter. The short initial triserial stage as typical for the genus ( Barnard, 1963) has not been observed due to inadequate sections. The biseriate chambers are subdivided by both horizontal and vertical (= radial) partitions. It appears that the horizontal partitions (rafters) are not present in the early part but appear later during ontogeny. In contrast hereto, the radial vertical partitions (up to three orders) seem to be present already in the early stage. The main vertical partitions (beams) stretch far into the test interior (length up to 0.2 mm in the middle part of the test), while the other orders (intercalary beams) are distinctly shorter. The rather short third order partitions (see ib in Fig. 5f ) reach up to 0.05 mm in length and are confined to the marginal part of the chamber.

Comparisons: Pseudotextulariella brevicamerata sp. nov. may exhibit the same number of biserial chambers, but within a test height half the size of the late Albian-Cenomanian P. cretosa ( Cushman, 1932) . This means, that the chamber height (= lumen) is distinctly reduced in the former. While the height of the chamber lumen often equals the thickness of the septa in P. brevicamerata sp. nov., it may be up to three times higher in P. cretosa . Also, the overall test dimensions (height, diameter) are larger in P. cretosa (Table 1). With its several orders of rafters (at least in the adult part), P. cretosa is structurally more complex than P. brevicamerata .

P. courtionensis Brönnimann, 1967 from the Valanginian of Switzerland exhibits an uncompressed test yielding rounded transverse sections ( Brönnimann, 1967, pl. 1, fig. 3, pl. 2, fig. 1). For all species of Pseudotextulariella however it appears that transverse sections through the juvenile part of the test are always subcircular and that a compression in the plane of biseriality appears throughout ontogeny. Like P. brevicamerata , the Swiss form also has only one order of rafters equally appearing in the adult part of the test. Note that in oblique sections, vertical partitions can be misidentified as rafters resulting in a (false) higher number of the latter ( Fig. 5l , left lower part). Exhibiting equivalent dimensions (height, diameter) compared with P. courtionensis , P. brevicamerata has more chambers due to reduced thickness of septa and chamber height (lumen). Last but not least, the different stratigraphy (late Berriasian-Valanginian vs. middle Cenomanian) as well as the different palaeogeographic locations (northern margin vs. southern margin, here Arabian Plate, of Neotethys) merits the differentiation of the new species described herein.

Remarks: The late Albian-Cenomanian Pseudotextulariella cretosa (Cushman) represents a typical taxon of the boreal realm (type-locality England; Germany, Frieg, 1989: Poland: Gawor-Biedowa, 1972) and the western part of the northern margin of Neotethys ( Romania: Bucur & Baltres, 2002).

Usually, it occurs in marly shelf lithologies (‘chalk facies’) delivering free, isolated specimens, but it may also be found in mixed siliciclastic-carbonate orbitolinid-bearing facies ( Bucur & Baltres, 2002). Pseudotextulariella brevicamerata sp. nov. instead occurs in foraminiferal wackestones-packstones of typical inner platform facies. The palaeogeographic setting of the Iranian Sarvak Formation refers its occurrence to the former southern margin of the Neotethys, i.e. the Arabian Plate (e.g., Ziegler, 2001). Both, Pseudocyclammina sarvakensis and Pseudotextulariella brevicamerata are further elements of the so-called ‘ Nezzazata -alveolinid’ assemblage zone sensu Wynd (1965) characterizing the late early to upper Cenomanian inner platform carbonates of the Sarvak Formation. For both taxa, the complete stratigraphic range could be modified by future new finds.

Figures

Fig. 5 Lower and Upper Cretaceous (Cenomanian) species of Pseudotextulariella Barnard, 1953. a-i, k Pseudotextulariella brevicamerata sp. nov., middle Cenomanian Sarvak Formation of SW Iran, Tang-e Darbast section (a-i) and Arman well-1 (k), thin-sections RAP 188 and AMN 3173.49 m. a, h-i Tangential sections. b, d-e, g Subaxial section, holotype specimen in e. c, k Oblique sections. f Fragmentary transverse section. j, l Pseudotextulariella courtionensis Brönnimann, 1967, Valanginian of Switzerland (from Brönnimann, 1967, pl. 1, figs. 1 and 5). m-n Pseudotextulariella cretosa (Cushman, 1932), transverse and axial sections (from Brönnimann, 1967, pl. 3, figs. 2 and 5). Abbreviations: b = beam, cha = chamber, fo = foramen, ib = intercalary beam, r = rafter, s = septum.

Fig. 2 a Simplified geological map of Iran (after Schlagintweit & Yazdi-Moghadam, 2021) showing the main tectonic subdivisions. b Road map of the Tang-e Darbast section (type-locality of Iraqia ultima Yazdi-Moghadam & Schlagintweit, 2022 and Simplorabanitina simplex Consorti, Schlagintweit, and Yazdi-Moghadam, 2022). c Road map of the Shahneshin section. d Position of Arman well-1. e Tectono-stratigraphic units of the Zagros belt (modified after Yazdi-Moghadam & Schlagintweit, 2021). The position of the studied sections is marked by an asterisk. Abbreviations: BF Balarud Fault, CEIM Central East Iran Microplate, HZF High Zagros Fault, KZF Kazerun Fault, MFF Mountain Front Fault, MZRF Main Zagros Revers Fault, MZT Main Zagros Thrust, SSZ Sanandaj-Sirjan Zone, UDMA Uromia Dokhtar Magmatic Arc, ZFTB Zagros Fold

Fig. 3 Lithostratigraphic log of the Tang-e Darbast section, the type locality of Pseudocyclammina sarvakensis sp. nov and Pseudotextulariella brevicamerata sp. nov., showing the distribution of some (larger) benthic foraminifera. a Neoiraqia insolita (Decrouez & Moullade), b Orbitolinopsis cenomaniensis Schlagintweit & Yazdi-Moghadam, c Conicorbitolina cf. conica (d’Archiac), d Mesorbitolina aperta (Erman), e Orbitolina ex gr. concava (Lamarck), f Rotorbinella mesogeensis (Tronchetti), g Nezzazata gr. gyra-conica (Smout), h Decastroia cf. serrakieli Vicedo & Piuz, i Myriastyla omanensis Piuz, Meister & Vicedo, j Chrysalidina gradata Orbigny, k Iraqia ultima Yazdi- Moghadam & Schlagintweit.