Pseudocyclammina sarvakensis, 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

Pseudocyclammina sarvakensis sp. nov.

Fig. 4 a-g

1969 Cyclammina sp. (?) – Sampò, pl. XLV, fig. 2.

2018 Pseudocyclammina rugosa – Omidi et al., pl. 2, fig. 5.

?2022 Pseudocyclammina rugose – Esfandyari et al., fig. 23l.

Derivatio nominis: The species name refers to the Sarvak Formation cropping out in southwestern Iran (Zagros Zone).

Holotype: Specimen illustrated in Figure 4b , equatorial section, sample RAP 181 .

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: Medium-sized (max. diameter 1.35 mm) species of Pseudocylammina with a planispiral, involute test displaying a rounded periphery. The spiral stage is well developed, and a tendency to uncoil in the final stage has not been observed. In subaxial sections, the test is slightly compressed (nautiloid morphology). Test surface as seen in equatorial section is smooth with much reduced to almost no sutural depressions. The chambers following the subspherical proloculus are arranged in 2.5 to 3.5 whorls displaying 14 to 16 chambers in the final whorl. The dimensions for the four measured proloculi diameters (0.110 mm, 0.125 mm, 0.140 mm and 0.300 mm) suggest a test dimorphism that needs further clarification. The early postembryonic chambers are subrhombohedric later with increasing width become recurved. The chamber lumen is markedly higher as the thickness of the septa and also of the wall. Multiple and tiny foramina (diameter 20-35 µm), with parallel arrangement in axial sections and septal spaces about twice the width of the former ( Fig. 4f ). Wall agglutinated, alveolar.

Comparisons: As can be deduced from the synonymy, the new species has been confounded with Pseudocyclammina rugosa (d’Orbigny, 1850) . These assignments however must have been made on the basis simplicity as P. rugosa represented the only species of the genus described (until now) from Cenomanian strata. However, with respect to the traditional specific criteria, P. sarvakensis nov. sp. and P. rugosa are by no means comparable. According to Maync (1952), P. rugosa attains 3.1 to 3.8 mm millimeters in length, displaying five to six large inflated chambers in the last whorl ( Fig. 4i ). It is worth mentioning that already Henson (1948, p. 10 and 15) mentioned that the wall structure of ‘ Lituola ’ rugosa d’Orbigny and Pseudocyclammina “ are essentially similar in construction ” and that “ separation of the two genera is somewhat uncertain ”. Another upper Cretaceous representative of Pseudocyclammina is P. massiliensis described by Maync (1959) from the Santonian of southeastern France ( Fig. 4h ). This is also a comparably large species commonly displaying uncoiled elongated tests (up to 2.3 mm) with five to seven chambers in the final whorl. So far no specimen of P. sarvakensis displaying uncoiled test has been observed. The number of chambers in the final whorl might differentiate P. sarvakensis from all other Upper Jurassic–Lower Cretaceous Pseudocyclammina species ( Maync, 1959, tab. 1 ; Banner & Whittaker, 1991). For example, the Upper Jurassic-Lower Cretaceous type-species Pseudocyclammina lituus ( Yokoyama, 1890) typically has 8 to 12 chambers in the last whorl ( Banner & Whittaker, 1991). The Lower Cretaceous (Aptian-Albian) P. hedbergi Maync, 1953 and P. vasconica , 1959 have 4-5 and 7-8 chambers in the final whorl. Pseudocyclammina sphaeroidea Gendrot, 1968 (= Mayncina sphaeroidea acc. to De Castro, 1991) described from the upper Santonian of southeastern France is distinctly smaller than P. sarvakensis with test length of 0.5 to 0.6 mm, often uncoiling ( Fig. 4 j-m). The youngest record of the genus Pseudocyclammina seems to be from the upper Campanian ( Parente, 1994, pl. 1, fig. 5, Pseudocyclammina sp. , in our opinion referable to P. massiliensis Maync ).

Figures

Fig. 4 Upper Cretaceous species of Pseudocyclammina Yabe & Hanzawa, 1926; note the different scales. a-g Pseudocyclammina sarvakensis sp. nov., middle Cenomanian Sarvak Formation of SW Iran, Tang-e Darbast section, thin-section RAP 181 (b, d-f), and Shahneshin section, thin-section AKHS 97 (c, g). a Equatorial section, microspheric specimen? (from Sampò,1969 illustrated as Cyclammina sp. (?) in pl. XLV, fig. 2). b Equatorial section, holotype. c, e Oblique sections. d Subaxial section. f Oblique tangential section. g Oblique equatorial section, megalospheric specimen? h Pseudocyclammina massiliensis Maync, early-middle Campanian of Brač Island, Croatia. i Pseudocylammina rugosa (Orbigny), equatorial section, Cenomanian of W France (from Maync, 1952, pl. 12, fig. 10). j-m Pseudocyclammina sphaeroidea Gendrot, Upper Cretaceous (?Coniacian) of Austria (from Schlagintweit, 1992, pl. 1, figs. 13-16). Subaxial section (j), equatorial section of a specimen with uncoiling final stage (k), equatorial section (l), equatorial section slightly oblique (m).

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.