Orbitolina qatarica Henson, 1948

Orbitolina qatarica Henson, 1948 View in CoL

T 1948 Orbitolina concava (Lamarck) var. qatarica – Henson, p. 66-67, pl. 5, fig. 7-10 (non fig. 11 = Mesorbitolina aperta ), text-fig. 10. “Cenomanian”, subsurface Qatar, but more likely late Albian (see text).

Non 1969 Orbitolina concava (Lamarck) qatarica Henson – Sampò, pl. 39, figs. 16-17, 19-21 (= Palorbitolinoides hedini Cherchi & Schroeder fide Schlagintweit et al., 2022 ).

Non 1976 Orbitolina concava qatarica – Ho et al., p. 20, pl. 3, fig. 4, 1-16. (= Palorbitolina ultima or Palorbitolinoides fide Rao et al., 2017 ).

?1993 Orbitolina qatarica - Hewaidy & Al-Hitmi, p. 479, pl. 5, fig. 4-7. Late Albian, subsurface Qatar.

?1996 Orbitolina qatarica – Mohammed, p. 66-68, pl. 7, fig. 8-9; pl. 8, fig. 1-3. Late Albian, subsurface southern Iraq.

2000 Orbitolina qatarica – Simmons et al., p. 423-424, pl. 2, figs. 7-9. Most likely late Albian, subsurface Qatar (see text).

2018 Orbitolina qatarica – Luger, p. 75-77, pl. 8, fig. 11- 14, pl. 9, fig. 1-5. Early Cenomanian, Somalia.

Diagnostic features: An Orbitolina with a proloculus of max diameter c. 0.20mm, and which is often convex upwards with a flat base. The embryonic apparatus diameter is 0.72 – 0.75mm. The supra-embryonic zone is markedly conical, relatively thick and highly subdivided. The sub-embryonic zone is thin, convex and highly subdivided. Radial zone chamber passages are almost exclusively rectangular in section.

Remarks: Initially introduced as a variety of O. concava by Henson (1948), it was elevated to subspecies then species status by a number of workers (e.g., Schroeder, 1962, 1975; Simmons et al., 2000; Luger, 2018). In his review of O. concava and O. sefini, Schroeder in Schroeder & Neumann (1985) considered O. qatarica as morphologically intermediate between them. Simmons et al. (2000) considered it as a distinct species, that whilst having mostly rectangular chamber passages and a large embryonic apparatus (both typical of O. concava ), the embryonic apparatus was sufficiently distinct in subconical form and highly divided supra-embryonic and sub-embryonic zones. Luger (2018) independently came to similar conclusions, and emphasised the relationship to O. sefini , as opposed to O. concava , noting that some specimens could only be considered “ O. sefini / qatarica ”. Nonetheless, he recorded viable specimens from the early Cenomanian of Somalia (including an invalid lectotype – not from original syntypes).

Within the syntypes of Henson (1948) there is a specimen (pl. 5, fig. 11 therein) that has been regarded as aberrant ( Simmons et al., 2000; Luger, 2018). In fact, this specimen conforms to Mesorbitolina aperta (Erman) , highlighting the mixture of taxa that can occur in several syntypic series of Henson (1948) ( Simmons et al., 2000).

As with all species of Orbitolina , multiple, good quality axial and tangential sections are required to confirm identity, and as such, records of its stratigraphic range are hard to confirm. Misidentifications also occur, for example by Sampò (1969) from the Albian of the Iranian Zagros that include Palorbitolinoides hedini ( fide Schlagintweit et al., 2022 ). Older records (e.g., Schroeder, 1962; Berthou & Schroeder, 1978) might be better incorporated in the modern concept of O. sefini or O. hensoni .

Stratigraphic range: Latest Albian – early Cenomanian (confident but scarce), uncertain in middle Cenomanian. The type locality in the subsurface of Qatar was considered Cenomanian by Henson (1948), supported by the co-occurrence with Praealveolina tenuis . Although this is oft-cited, Le Blanc (2015) showed that the type material in fact comes from the Mauddud Formation (late Albian according to Bromhead et al., 2022) and that the P. tenuis records represent caving. See also effective topotypes illustrated by Hewaidy & Al-Hitmi (1993), although their identity is uncertain. It is also reported from the Mauddud of Qatar by El Beialy & Al-Hitmi (1994), but the illustrations cannot be identified. Hofker (1963) illustrated the embryonic apparatus of each of three specimens of what he termed “ Orbitolina lenticularis ” from the type locality (but not the type horizon?) of O. qatarica (pl. 17, fig. 11-13). Their identity is uncertain but seems unlikely to be Orbitolina sensu stricto.

Owen & Nasr (1958) and van Bellen et al. (1959) reported (without illustration) the species from the Rumaila Formation of southern Iraq. If correct, this would imply an age as young as middle Cenomanian (Bromhead et al., 2022). Many other records from southern Iraq are from the late Albian Mauddud Formation ( Noori et al, 2016; Ezzulddin & Ibrahim, 2022; Shakir & Mousa, 2023), although only those of Mohammed (1996) are potentially plausible, others indeterminate or being ascribable to Orbitolina spp. at best. This includes a record from the Mauddud in southern Iran ( Farsi et al., 2022), although the authors regard this as proof of a middle Cenomanian age, counter to regional evidence.

It was also recorded from the late Albian Qamchuqa Formation of N. Iraq (Ameen & Gharib, 2014), but the illustrations are uncertain.

Records from the early Cenomanian of Spain ( Ramirez del Pozo, 1972) and Tibet ( Ho et al., 1976; Yang et al., 1982; BouDagher-Fadel et al., 2017; Xu et al., 2019, 2021) are either not illustrated or misidentified. The records of Ho et al. (1976) from Tibet are considered to be of the Palorbitolina ultima - Palorbitolinoides hedini lineage by Rao et al. (2017).

In summary, the potential stratigraphic range is late Albian – early Cenomanian, possibly middle Cenomanian, although more work is needed to confirm this.

Palaeogeographic distribution: In common with other Orbitolina species, confirmed records of O. qatarica remain few and so far, restricted to Qatar and Somalia (southern Neotethys). Other possible occurrences are reported from southern Iraq.