Biconcava bentori Hamaoui, 1965

SIMMONS, MICHAEL & BIDGOOD, MICHAEL, 2023, “ Larger ” Benthic Foraminifera Of The Cenomanian. A Review Of The Identity And The Stratigraphic And Palaeogeographic Distribution Of Non-Fusiform Planispiral (Or Near-Planispiral) Forms, Acta Palaeontologica Romaniae 19 (2), pp. 39-169 : 53-56

Biconcava bentori Hamaoui, 1965 emended Hamaoui & Saint-Marc, 1970

Reference Illustration & Description

Hamaoui (in Schroeder & Neumann, 1985), Pl. 13, figs. 1-7, p. 34.

The valid source of the original description of the genus Biconcava and its type species B. bentori has been disputed. They were described and illustrated (in a limited way) as a new genus and species by Hamaoui (1965) in a report for the Israel Geological Survey on the type Hazera Formation (Cenomanian) (see also Arkin et al., 1965; Hamaoui, 1966; Arkin & Hamaoui, 1967; Lipson-Benitah, 2009). However, Hamaoui & Saint-Marc (1970) presented additional description and illustrations (Plates 18-21) and regarded this as the type description (see also Hamaoui in Schroeder & Neumann, 1985). Nonetheless, as noted by Loeblich & Tappan (1988), the 1965 citation by Hamaoui is valid, thus we adopt the type designation as “ Hamaoui, 1965 emended Hamaoui & Saint-Marc, 1970 ” for both genus and species.

The illustrations and description in Hamaoui in Schroeder & Neumann (1985) are adequate for reference purposes and mostly derive from Hamaoui & Saint-Marc (1970) and Saint-Marc (1974a). See the Species Key Chart (Appendix) for diagnostic and other characteristics.

A biumbilicate form with up to 24 chambers in the final whorl, and about three and a half whorls (up to 4) in adult specimens, it is superficially similar to Biplanata peneropliformis . B. bentori has a more lenticular test (i.e., is less flattened than B. peneropliformis ), a slower rate of chamber size increase, and possesses a characteristic Vshaped chamber cross-section which B. peneropliformis lacks. The internal dental plate in Biconcava as mentioned by Hamaoui & Saint-Marc (1970 p. 302) is simply bifurcated but becomes complete and occupies the medial plane of the chamber in Biplanata . The plate is very small and is shown and annotated in Hamaoui & Saint-Marc on one figure only (1970, plate 21 figure 1). However, its presence is disputed by Loeblich & Tappan (1988). Biconcava can be distinguished from other planispiral taxa such as Daxia (which is less evolute and has no internal dental plate) and Charentia (which has a pseudokeriothecal test structure and no internal dental plate).

Biconcava is also distinguished from Daxia in minor apertural details (an opening in a vertical groove rather than a single opening just above the base of the apertural face) but these are almost impossible to distinguish in thin-section.

A new species described as Biconcava ribbata by Shahin & Elbaz (2013) from the late Cenomanian in two sections from Sinai, Egypt appears to conform externally to the generic concept of Biconcava but is not supported by internal views or comments about the dental plate (if present). It does not appear to have been recorded subsequently and the “ribbed” appearance is most likely a taphonomic effect on B. bentori specimens (Dr Lorenzo Consorti, pers. comm., 2023).

Records by Sinanoglu & Erdem, 2016; Sinanoglu et al., 2020 and Sinanoglu, 2021, of occurrences of B. bentori (along with other mid Cretaceous taxa) together with demonstrably Maastrichtian taxa in the Garzan Formation of Turkey are intriguing. Some appear superficially similar to B. bentori , but the assigned age is clearly anomalous and an approximate 30 My age-range for a single species would seem unusual. Additional illustrations of her specimens kindly provided by Dr. Sinanoglu to the authors suggests that these specimens may be of a Biconcava , but if so, probably not B. bentori sensu Hamaoui & Saint-Marc (1970) and Saint-Marc (1974a). In equatorial section, the type B. bentori has between 18-24 chambers in the final whorl (the Turkish specimens have no more than 12) and the chambers of typical B. bentori are short and high when viewed from the side compared with the equi-dimensional, almost “square” chambers of the Turkish material. The possibility of mid Cretaceous homeomorphs in the Maastrichtian has been considered ( Schlagintweit & Yazdi-Moghadam, 2022a, who recognise the genus Neodubrovnikella in the Cenomanian and Maastrichtian with a ‘ghost range’ in between) and this may be an example of that.

The specimens identified as Biconcava sp. by Tasli et al. (2006) from the Coniacian-Santonian of the Cehennemdere Formation of southern Turkey ( Fig. 7 ; A & B internal views) would appear superficially at least to conform to the generic concept, but in thin-section the number of chambers in the final whorl is fewer than in the type description and illustration for B. bentori .

Stratigraphic Distribution

Early - late Cenomanian.

B. bentori was regarded by Hamaoui (in Schroeder & Neumann, 1985) as ranging from the middle Cenomanian to the Cenomanian-Turonian boundary (see also Arnaud et al., 1981 with tentative extensions into the early Cenomanian and basal Turonian). Plausible illustrated records of B. bentori by Bravi et al. (2004) from central Italy, Ghanem et al. (2012) from Syria and Saint-Marc (1981) from Lebanon indicate the presence of this species in early Cenomanian sediments, as old as the base of the stage. This species is commonly recorded in the literature, but most records are not substantiated by illustration. Similarly, few records are supported by independent age verification, which hinders assessment of the true stratigraphic range. Overall, records are almost entirely confined to the Cenomanian although these are skewed towards the middle – late Cenomanian.

Rare, anomalously younger records (e.g., Ghaseminia et al., 2016 – Coniacian to Santonian; Luperto-Sinni, 1976; Luperto-Sinni & Richetti, 1978 – Santonian – Campanian; Šribar & Pleničar, 1990 – late Turonian; Velić, 2007 – early Cenomanian to early Campanian; Solak et al., 2015 – Turonian to Campanian) are not substantiated by plausible illustrations (see also remarks above concerning occurrences reported in the Maastrichtian by Sinanoglu and others).

Weidich & Al-Harithi (1990) illustrate a plausible form from Jordan, noting that the species has middle Albian to Cenomanian range there. This is the most viable evidence that the species ranges older than Cenomanian, but the specimen illustrated is actually from Cenomanian strata. An illustrated record from an interval of “latest Albian to early Cenomanian” age from the Sarvak Formation of the Iranian Zagros ( Mohseni & Javanmard, 2020) is not of B. bentori (instead a simple unrelated taxon). Thus, illustrated records from Albian strata are lacking.

Those references which are supported by definite (or at least plausible) illustrations mostly indicate a middle – late Cenomanian age (or at least general undifferentiated Cenomanian age). These include:

Morocco: Ettachfini & Andreu (2004) and Ettachfini (2006) illustrate a form attributed to Moncharmontia aff. apenninica from the late Cenomanian of Morocco, but which seems more compatible with B. bentori (see also unillustrated by Piuz & Meister, 2013).

Tunisia: Bismuth et al. (1981) (see also unillustrated by Touir et al., 2017)

Portugal: Berthou (1973)

Italy: Foglia (1992); Tentor et al. (1993); Tentor & Tentor (2007) and Chiocchini et al. (2012) (see also an uncertain illustration by Simone et al., 2012; and unillustrated by Chiocchini, 2008a; Chiocchini et al., 2008; Di Stefano & Ruberti, 2000; Borghi & Pignatti, 2006; Spalluto & Caffau, 2010; Spalluto, 2011; Consorti et al., 2015 and Frijia et al., 2015 - the latter reference is useful as the occurrences it describes are well-calibrated to ammonite zones and carbon isotope data as upper middle – late-but-not-latest Cenomanian)

Croatia: Velić & Vlahović (1994) (see also unillustrated by Husinec et al., 2009 and Korbar et al., 2012)

Serbia and Kosovo: Radoičić (1974a)

Greece: Fleury (1971), Charvet at al. (1976) (see also unillustrated by Fleury, 1980 and Zambetakis-Lekkas, 2006)

Southern Turkey: Tasli et al. (2006); Sari et al. (2009); Solak et al. (2019); Solak (2021) (see also uncertain records by Koç, 2017; Simmons et al., 2020 b and Solak et al., 2020)

Egypt / Sinai: Kerdany et al. (1973) as “ Peneroplis turonicus ”; El-Sheikh & Hewaidy (1998) (see also uncertain records by Samuel et al., 2009; Orabi et al., 2012 and Shahin & Elbaz, 2013; and unillustrated by Kuss, 1994; Ismail & Soliman, 1997; Bauer et al., 2001; Bachmann et al., 2003; Ismail et al., 2009; Cherif et al., 1989; Orabi & Hamad, 2018; El Baz & Khalil, 2019; El Baz & Kassem, 2020)

Iranian Zagros: Sartorio & Venturini (1988); Rahimpour-Bonab et al. (2012); Afghah et al. (2014); Ezampanah et al. (2020); Yazdi-Moghadam & Schlagintweit (2020, 2021) and Schlagintweit & Yazdi-Moghadam (2020, 2021) (see also unillustrated by Fourcade et al., 1997; Afghah & Fadaei, 2014; Omidvar et al., 2014a, b; Consorti et al., 2015; Dehghanian & Afghah, 2021; Omidi et al., 2021 and Mohajer, 2022a, 2022b).

Southern Iraq: An illustration of Pseudorhapydionina laurinensis by Al-Dulaimy et al., (2022) from the late Cenomanian Mishrif Formation is probably B. bentori .

Saudi Arabia: Dr Wyn Hughes (pers. comm., 2022)

Other illustrated references include occurrences which are difficult to verify based on preservation or orientation of the thin-section cut. As such they are classed as “possible” B. bentori at best. These include Omaña et al. (2019) from Mexico (see also unillustrated by Hernández-Romano et al., 1997; Aguilera-Franco et al., 2001; Aguilera-Franco, 2003 (but a specimen illustrated as Moncharmontia apenninica may be B. bentori ); Aguilera-Franco & Hernández-Romano, 2004 and Aguilera-Franco & Allison, 2004); Andrade (2018) from Portugal; Božović (2016) from Montenegro; and Ghanem & Kuss (2013) from Syria (see also unillustrated by Mouty et al., 2003) from Syria. Most assigned ages are middle – late Cenomanian with occasional early Cenomanian.

Illustrated references which are not, in fact, of B. bentori include Decrouez (1978) from Greece (nothing compatible in photomicrograph); Velić & Sokač (1979) from the Dinarides (simple unrelated indeterminate form); Ghaseminia et al. (2016) (simple unrelated indeterminate form), Assadi et al. (2016) [= Praetaberina bingistani ], Kiarostami et al. (2019) (indeterminate, but not biconcave), Mohajer et al. (2021a) (indeterminate but not biconcave), Asghari et al., (2022) (indeterminate, but not biconcave) and Esfandyari et al. (2023) (indeterminate but incompatible with B. bentori : too few chambers) from the Iranian Zagros, and Ezzulddin & Ibrahim (2022) (simple, probably trochospiral foraminifera) from southern Iraq.

References which record B. bentori , but which are not substantiated by illustration are numerous – more than double those with definite, plausible and possible illustrations. The occurrences are, however, also predominantly assigned to a middle – late Cenomanian age with occasional early Cenomanian records, as well as some possible early Turonian records although the latter are questionable. Those not yet mentioned above include Diaz Otero et al. (2001) from Cuba; Berthou & Lauverjat (1979), Crosaz-Galletti (1979), Berthou (1984a, 1984b), Calonge et al. (2002, 2003), Cabral et al., (2008), Caus et al. (2009), Vicedo et al. (2011) and Consorti et al. (2016b) from Iberia; Deloffre & Hamaoui (1979) from France; Boix et al. (2009) from the Mediterranean or western Tethys; Schulze (2003) and Schulze et al. (2004) from Jordan; Mohammed (2007), Al-Dulaimy & Al-Sheikhly (2013), Al-Dulaimy et al. (2022) and Al-Salihi & Ibrahim (2023) from southern Iraq; Youssef et al. (2019) from Kuwait; Menegatti (2004) from Dubai; and Scott et al. (2000), Piuz & Meister (2013) and Piuz et al. (2014) from Oman.

Cenomanian Paleogeographic Distribution

Neotethys and?Caribbean.

The records mentioned above substantiate by illustration definite occurrences in the Zagros-Turkey-North Africa, Eastern and Western Mediterranean region. There are numerous additional records unverified by illustration that could, if proven by new data, further demonstrate the geographic distribution of this species and extend it much more widely. These additional records (west to east) include from Mexico, Cuba, Iberia, Iraq, Kuwait and Oman (see above for references).

Figures

Fig. 7 Representative illustrations of Daxia cenomana: a Equatorial section, Arnaud-Vanneau & Prestat in Schroeder & Neumann (1985, pl. 1, fig. 2, France); b Axial section, Arnaud-Vanneau & Prestat in Schroeder & Neumann (1985, pl. 1, fig.7, France).