Orbitolina concava (Lamarck) var. sefini, Bidgood & Schlagintweit & Simmons, 2024

Bidgood, Michael, Schlagintweit, Felix & Simmons, Michael, 2024, The Genus Orbitolina D’Orbigny, 1850 (Larger Benthic Foraminifera) And Its Constituent Species: Notes On Identity And Stratigraphic Ranges, Acta Palaeontologica Romaniae 20 (2), pp. 33-59 : 39-40

Orbitolina sefini Henson, 1948

T 1948 Orbitolina concava (Lamarck) var. sefini var. nov. – Henson, p. 64-65; pl. 5, fig. 1-2 (non 3-4 = Conicorbitolina conica fide Schroeder in Schroeder & Neumann, 1985) “Cenomanian”, Iraq. Could be late Albian.

? 1962 Orbitolina (Orbitolina) concava qatarica – Schroeder, p. 191-193, pl. 20, fig. 11; pl. 21, fig. 2. Early Cenomanian, Spain.

1985 Orbitolina (Orbitolina) sefini - Schroeder in Schroeder & Neumann, pl. 30, fig. 1-3 “Cenomanian”, Iraq. Could be late Albian.

Non 1985 Orbitolina (Orbitolina) sefini – Schroeder in Schroeder & Neumann, p. 66-68, pl. 30, fig. 4 -8. Probably Orbitolina hensoni .

Non 1992 Orbitolina sefini – Simmons & Williams, pl. 1, fig. 3-5. Probably O. hensoni .

?1999 Orbitolina sefini Henson – Cherchi & Schroeder, p. 20, pl. 2, figs. 1-8, pl. 3, figs. 1-3. Early Cenomanian, Spain.

2000 Orbitolina sefini – Simmons et al., p. 423, pl. 1, fig. 8; pl. 2, figs. 3-5; pl. 4, fig. 10. “Cenomanian”, Iraq. Could be late Albian.

Non 2004 Orbitolina sefini – Schulze et al., text-fig. 10b. Indeterminate orbitolinid, but not Orbitolina sp.

Non 2013 Orbitolina sefini – Ghanem & Kuss, pl. 14, fig 5-6 (= Conicorbitolina sp. ), 7 (= Cuneolina or Dicyclina sp. ), 9 (= indeterminate orbitolinid)

Diagnostic features: An Orbitolina with a proloculus of max diameter c. 0.25mm and an embryonic apparatus diameter of 0.45 – 0.60mm. The supra-embryonic zone is highly subdivided. Sub-embryonic zone thin. Radial zone chamber passages are initially triangular in section, becoming rectangular in later chambers. This variation is also observed in different generations (triangular in macrospheric, elliptical/subrectangular in microspheric).

Remarks: First defined as a variety (= subspecies) of O. concava by Henson (1948) based on material from Sefin Dagh in NE Iraq. As noted by a number of workers (e.g., Schroeder in Schroeder & Neumann, 1985; Simmons et al., 2000) the original description and illustration of the species included a variety of taxa recognised using modern concepts of Orbitolininae , further amplified by assessment of material in the F.R.S. Henson and Associates Collection in the Natural History Museum, London. Nonetheless, Schroeder in Schroeder & Neumann (1985), Schroeder et al. (1986) and Cherchi & Schroeder (1999) in a revaluation of the species considered that the type material included an Orbitolina distinct from O. concava by virtue of a smaller embryonic apparatus and exclusively triangular chamber passages (in megalospheric forms). The exclusively triangular nature of the chamber passages was refuted by Simmons et al. (2000) who considered that the chamber passages are initially triangular but become rectangular in later adult chamber layers. This is still distinct from O. concava and O. qatarica that have exclusively rectangular chamber passages. Simmons et al. (2000) introduced Orbitolina hensoni for material that has only triangular chamber passages based on “ Orbitolina cf. concava” sensu Henson (1948) .

Despite the work of Schroeder in Schroeder & Neumann (1985), Schroeder et al., (1986), Cherchi & Schroeder (1999) and Simmons et al. (2000) identification of O. sefini remains challenging, not least because the syntypes of Henson (1948) only include poor or somewhat oblique sections through the embryonic apparatus as illustrated by Simmons et al. (2000) ( Henson, 1948 illustrated none). Schroeder in Schroeder & Neumann (1985) and Schroeder et al. (1986) illustrated axial sections of the embryonic apparatus based on material from western Europe thought to be O. sefini , but now might be better attributable to O. hensoni following Simmons et al. (2000).

Cherchi & Schroeder (1999) made an important observation in that in material considered by them to be O. sefini from the early Cenomanian of Spain, chamber passage shape varies between macrospheric and microspheric generations. In macrospheric forms they considered chamber passage shape to be exclusively triangular, but in microspheric forms to be elliptical to sub-rectangular (illustrations show some triangular passages as well). This complicates species determination, as care needs to be taken to assess the generation of specimens being observed. For example, in the type material of O. sefini from Iraq, it is not possible to determine the generation of specimens showing tangential sections and chamber passage shape. This is also true for O. hensoni , leading to the possibility that O. sefini and O. hensoni (sensu Simmons et al., 2000) represent different generations of the same taxon. This can only be resolved by study of more topotype material. Herein, we consider that the material of Cherchi & Schroeder (1999) is probably O. sefini but needs to be proven by comparison with additional type material.

Stratigraphic range: Very latest Albian – earliest Cenomanian (uncertain). Difficulties in the reliable identification of O. sefini challenge an assessment of its stratigraphic range. Henson (1948) considered the species to be Cenomanian, but this is partly due to the broad concept of the taxa he employed that might include other Cenomanian Orbitolininae (e.g., species of Conicorbitolina ). Furthermore, the Cenomanian age of the type locality at Sefin Dagh is unproven. It could certainly be late Albian. Schroeder in Schroeder & Neumann (1985) considered the species to be latest Albian – earliest Cenomanian and Schroeder et al (1986) recorded it from the late Albian of SW England supported by ammonite records. However, these records are now better assigned to O. hensoni .

Lopez-Horgue et al. (2009) consider that the range may extended to low in the late Albian of Spain (variscum Zone, binum subzone = approximately mid- pricei zone fig. 3 herein) because of ammonite co-occurrences, but confirmation of the identity of O. sefini is uncertain (= Orbitolina spp. herein). Specimens of “ Orbitolina (Orbitolina) concava qatarica ” illustrated by Schroeder (1962) from the early Cenomanian of Spain may be this species, given the embryonic apparatus dimensions (total diameter 0.68 mm and proloculus diameter 0.26 mm) and chamber passages that appear to grade from triangular to rectangular.

The species has been extensively reported from the Middle East, although many records are without illustration, or only supported by illustrations that are effectively inadequate to determine species. Simmons & Hart (1987) illustrated an uncertain specimen from the lower Natih Formation of Oman (latest Albian – earliest Cenomanian according to Bromhead et al., 2022). This is equivalent to the Mauddud Formation recognised in many parts of Arabia, and from which O. sefini is frequently reported, although seldom with supporting definitive illustration (see for example, Mohammed, 1996; Noori et al., 2016; Youssef et al., 2019; Navidtalab et al., 2020; Manhi & Alsultani, 2021; Shakir & Mousa, 2023 – all unconfirmed).

Al-Mamory & Al-Dulaimi (2020) Ameen & Gharib (2014) report the species from the Qamchuqa Formation of northern Iraq, but the illustrations are indeterminate.

The species has been reported from the early Cenomanian of Israel ( Frank et al., 2010), whilst illustrations by Hamaoui (1965) from Israel of “ Orbitolina cf. O. concava sefini ” are probably of Conicorbitolina . Records from the middle – base late Cenomanian of NW Syria ( Ghanem & Kuss, 2013) are also most likely of Conicorbitolina and can be discounted from an assessment of stratigraphic range. A record from the late Albian – early Cenomanian Naur Formation of Jordan ( Schulze et al., 2004) is not of Orbitolina as illustrated.

Xu et al. (2023) illustrate the species (as “cf.”) from the late Albian upper Khazdumi Formation of the Iranian Zagros, but the specimen is best considered as Orbitolina spp. as defined herein. Likewise, Luger (2018) confidently reports the species from the late Albian – early Cenomanian of Somalia, but the illustrations are probably better assigned to Orbitolina spp.

Palaeogeographic distribution: As with assessment of stratigraphic range, difficulties in the reliable identification of O. sefini challenge an assessment of its palaeogeographic distribution. Iraq remains the only area where its presence – poor definition notwithstanding – has been confirmed (southern Neotethys), with other possible occurrences in Oman and Spain.