Moncharmontia apenninica (De Castro, 1966)

Reference Illustration & Description

[Note: also misspelled as Montcharmontia in several publications]

De Castro (1966), Figs. 5-6, Pls. I-V (not pl. III, figs. 4- 8), p. 328-333.

The original comprehensive description (De Castro, 1966, 1967) of the genus and two species (Moncharmontia apenninica (type species) and Moncharmontia compressa De Castro) describes a planispiral (though the final whorl may be slightly irregular compared to the initial planispiral coiling), involute and biumbilicate test with a wall that consists of “one calcareous microgranular layer, apparently perforate” (i.e., pseudokeriothecal) (see also Tešović et al., 2001). The aperture is cribrate with numerous small circular openings in the middle and lower parts of the apertural face – well illustrated in thin-section examples by Chiocchini et al. (2012) and Arriaga et al. (2016). Up to ten chambers can be present in the final whorl, with up to two and half whorls present. In equatorial section, the chambers have a trapezoidal shape, and the septa are straight to slightly convex. On average, the equatorial diameter of shells with two entire whorls is 0.47 mm and the maximum thickness is 0.27 mm (Arriaga et al., 2016). See the Species Key Chart (Appendix) for diagnostic and other characteristics.

The genus Fleuryana is very similar but differs in by having slightly fewer chambers in the final whorl (8 cf. 9- 10), thinner walls and a single, basal aperture (Solak et al., 2020, see Appendix).

Stratigraphic Distribution

Upper middle Cenomanian – Maastrichtian.

The FAD of M. apenninica has long been considered (e.g., Sartorio & Venturini, 1988; Loeblich & Tappan, 1988; Moro & Jelaska, 1994; Koch et al., 1998; Korbar & Husinec, 2003; Velić, 2007; Sari et al., 2009; Chiocchini et al., 2012; Frijia et al., 2015; Arriaga, 2016; Arriaga et al., 2016; Özkan & Altiner, 2019; Solak et al., 2020) to represent the appearance of a new taxon in the Turonian and has been related to faunal renewal after the largescale extinction event that occurred towards the end of the Cenomanian, linked to OAE2 and calibrated to the geslinianum ammonite zone (Parente et al., 2008).

Nonetheless, a plausible specimen of M. apenninica was illustrated by Bignot & Poisson (1974) from undoubted Cenomanian strata in the Turkish Taurides. Moreover, plausible illustrated occurrences in Cenomanian strata were recently recorded by Schlagintweit & Yazdi-Moghadam (2021) from the Cenomanian part of the Sarvak Formation of the Iranian Zagros. Co-occurrence with Chrysalidina gradata, Cisalveolina fraasi and Simplalveolina simplex (Reichel) clearly points to a Cenomanian age. Also, Mohajer et al. (2021a) illustrated possible M. apenninica from the late Cenomanian part of the Sarvak Formation (and note its occurrence in the Turonian part), whilst Rikhtegarzadeh et al. (2017) mention Moncharmontia sp. from the Cenomanian part of the Sarvak, but provide no illustration.

Therefore, Schlagintweit & Yazdi-Moghadam (2021) have suggested the FAD of M. apenninica occurs “somewhere in the upper part of the middle Cenomanian”. They also pointed out Cenomanian occurrences in Mexico (Omaña et al. (2012, 2013) but these are not supported by illustration - see also Aguilera-Franco et al., 2001; Aguilera-Franco & Romano, 2004; Aguilera-Franco & Allison, 2004). There is also an illustrated, but misidentified record (possibly Biconcava bentori) (Aguilera-Franco, 2003).

Koç (2017) mention M. apenninica in association with a clearly Cenomanian foraminiferal assemblage from the Turkish Taurides. Plausible specimens are illustrated, but these may be from younger stratigraphy (the caption is unclear). Also, from the Taurides, Solak et al. (2020) describes “ Moncharmontia? sp.” from the uppermost Cenomanian (see also Sağaltici & Koç (2021) unillustrated). The specimens are almost certainly this genus, but species identification is not possible. Shanin & Elbaz (2013) record the species from the Cenomanian of Sinai, but the disaggregated specimens illustrated cannot confidently be identified as this species. Another (but unillustrated) record from the Cenomanian comes from the Natih Formation of Oman by Piuz & Meister (2013). 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 Biconcava bentori.

Records from strata attributed to the Turonian should be checked for “circular reasoning” – i.e., a Turonian lower age limit is attributed to M. apenninica (and the strata it is found in). For example, the illustrations of M. apenninica from the upper Derdere Formation of Turkey attributed to the Turonian by Özcan & Altiner (2019) are reasonably plausible. However, these records co-occur with Cuneolina pavonia d’Orbigny, Nezzazata simplex Omara and Nezzazatinella picardi (Henson); all taxa that could be as old as Cenomanian (see Simmons et al., 2020b for further discussion on the age attribution of the Derdere Formation).

Similar arguments can be applied to the records by Rahimpour-Bonab et al. (2012, 2013) and Omidvar et al. (2014a, 2014b) from the Sarvak Formation in the Iranian Zagros where the presence of M. apenninica is used to infer a Turonian age. These records may be Turonian, but evidence other than the occurrence of Moncharmontia (plausibly illustrated by these authors) should be sought. Recent strontium isotope calibrated ages (Mehrabi et al., 2022a, 2022b) are helpful in this respect and suggest that some M. apenninica occurrences in the Iranian Zagros are indeed Turonian. Nonetheless, the statement by Omidvar et al. (2014a, 2014b) that M. apenninica is an index fossil for ages no older than Turonian in the Iranian Zagros is incorrect. On the other hand, there is little doubt that the local inception of M. apenninica (for example in the type area of the Italian Apennines) occurs within the Turonian (e.g., Frijia et al., 2015). It may be that as suggested by Schlagintweit & Yazdi-Moghadam (2021) the species arose elsewhere within the Cenomanian and migrated to the Mediterranean region in the Turonian, occupying palaeoecological niches vacant by the Cenomanian/Turonian boundary extinction event. Lack of comprehensive supporting data is an ever-present challenge to LBF biostratigraphy.

The youngest verifiable record of this species is Maastrichtian (Sinanoğlu et al., 2020; Sinanoğlu, 2021, from Turkey). However, such a long range for a single species seems unusual and there may be further study required. On the other hand, Moncharmontia may have been very well adapted to the inner platform niche in which it lived, and as a relatively simple form, persisted through environmental perturbations (see also Consorti & Rashidi, 2018, for a similar example in the genus Elazigina Sirel across the Cretaceous-Paleogene boundary).

Cenomanian Paleogeographic Distribution

Eastern Neotethys (and?Caribbean).

There are scattered records of M. apenninica from Cenomanian strata around Neotethys. However, the only proven occurrences are from the Turkish Taurides and the Iranian Zagros. Records from Sinai, Oman and south-east Turkey are unproven or of contentious age.

Records in strata younger than Cenomanian are numerous and widespread around Neotethys.