Pseudonummoloculina? cf. irregularis ( Decrouez & Radoičić, 1977 ) sensu Chiocchini et al. 2012 (Decrouez & Radoicic, 1977)

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 : 101

Pseudonummoloculina? cf. irregularis ( Decrouez & Radoičić, 1977) sensu Chiocchini et al. 2012

Reference Illustration & Description

Chiocchini et al. (2012), pl. 120, figs. 2-7.

N. irregularis was first described by Decrouez & Radoičić (1977) from Santonian -?Campanian rocks of Serbia. It is not, apparently, connected to the Recent form Biloculina irregularis d’Orbigny as apparently indicated in the World Foraminifera Database ( Hayward et al., 2020). There are, however, numerous records from the Quaternary of Nummoloculina irregularis (d’Orbigny) . If d’ Orbigny’s species is, in fact, a Nummoloculina , then the validity of Decrouez and Radoičić’s taxon would be questionable. See the Species Key Chart (Appendix) for diagnostic and other characteristics.

Chiocchini et al. (2012) recorded forms they assigned to Nummoloculina cf. irregularis from the Turonian (with a range up to the Santonian) but it is not clear why they chose the ‘cf.’ modifier as the illustrations look to be comparable with those of Decrouez and Radoičić (1977). The somewhat more ‘angular’ appearance of the periphery in equatorial view seems characteristic.

Solak et al. (2020) recorded forms they attributed to Pseudonummoloculina sp. from sediments just above the Cenomanian-Turonian boundary in Turkey. They stated that this taxon was “similar to Nummoloculina cf. irregularis of Chiocchini et al. (2012) ”. Their illustration of Pseudonummoloculina sp. is included within Figure 48 herein.

The illustrations of Chiocchini et al.’s (2012) and Solak et al.’s (2020) forms appear comparable and show a ‘nummoloculinid’ with a relatively large initial milioline coil and later coils which appear streptospiral and which may not achieve planispiral status until a very late growth stage.

For the practical reasons discussed above we have questionably assigned this taxon to Pseudonummoloculina . However, Schlagintweit & Rashidi (2016) note that N. irregularis sensu stricto is not atributable to Pseudonummoloculina and it is likely that a new genus will be needed to incorporate this species and others mentioned herein. Included in this revision could be Fischerina? carinata Peybernes , a distinctive simple biumblicate planispiral taxon described by Peybernes (1984) from the late Albian of Spain (Dr. Felix Schlagintweit, pers. comm., 2023). It is clear that much work needs to be undertaken to establish the taxonomy of the “nummoloculinids” sensu lato.

Stratigraphic Distribution

Cenomanian?/Turonian – earliest Santonian.

Chiocchini et al. (2012) record this taxon from the intra-early Turonian to the lower early Santonian of Italy (their illustrated specimens are from the Turonian). Solak et al. (2020) do not show the occurrence of this species on any range chart or section distribution chart, but their illustrated specimen (reproduced here) is attributed to their sample 206 which lies less than 1m above where they have placed the Cenomanian-Turonian boundary.

Records of “ Nummoloculina regularis ” from the Turonian uppermost Sarvak Formation of the Iranian Zagros ( Rahimpour-Bonab et al., 2013; Omidvar et al., 2014a) may well be P? cf. irregularis sensu Chioccini et al. 2012 , and provide support for the Turonian age assignment of these strata.

However, the specimen illustrated by Hottinger et al. (1989) as P. heimi (pl. 22, fig. 6, bottom right) from the Cenomanian of Mexico (see Fig. 44 (right) herein) is somewhat more similar to the illustration of P? cf. irregularis sensu Chiocchini et al. 2012 herein ( Fig. 48b ) and, if confirmed, suggests an older FAD for this taxon. This is a different viewpoint to Piuz & Vicedo (2020) who place the same Mexico specimen in tentative synonymy with their species Nummoloculinodonta akhdarensis from Oman (see below). This is an example of the difficulties in separating ‘nummoloculinid’ species in random thin section.

Cenomanian Paleogeographic Distribution

Central America?

Whilst this taxa is known from the Mediterranean in post-Cenomanian stratigraphy, the only possible Cenomanian record is from Mexico (see above).

Figures

Fig. 48 Representative illustrations of Pseudonummoloculina? cf. irregularis: a Subequatorial section, Chiocchini et al. (2012, pl. 1, fig. 3, Italy); b Subaxial section, Chiocchini et al. (2012, pl. 120,fig. 2, Italy); c Subequatorial section, Chiocchini et al. (2012, pl. 120, fig. 4, Italy); d Pseudonummoloculina sp. sensu Solak et al. (2020, fig. 14V, Turkey).

Fig. 44 Pseudonummoloculina heimi (Bonet) left – after De Castro (1987: fig. 3-2) and right –after Hottinger et al. (1989: pl. 22, fig. 6-part). Both specimens purported to show notched apertures. Neither specimen can, however, be attributed to heimi based on the criteria established by Piuz & Vicedo (2020, see text). Those authors place both specimens in tentative synonymy with their new species Nummoloculinodonta akhdarensis.