Planinummoloculina gnosi Piuz & Vicendo, 2020

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 : 101-104

Planinummoloculina gnosi Piuz & Vicendo, 2020

Reference Illustration & Description

Piuz & Vicedo (2020), fig. 3(A-U), p. 11-13.

P. gnosi is characterised by planispiral (occasionally slightly oscillating) coiling throughout, rather than having a distinctly milioline nepionic stage cf. Pseudonummoloculina? heimi and P. aurigerica . Apertural notches/crenulations similar to those seen in P. aurigerica are visible from the 5 th whorl onwards.

Piuz & Vicedo (2020) describe an adult test of 10-11 whorls with 3-4 chambers per whorl, but do not illustrate an equatorial view of their specimens. The test of P. gnosi is also reported as being larger (up to 3mm diameter) than both P. aurigerica and P? heimi . Axial/subaxial views show that P. gnosi has an axial profile broader to those of P? heimi and P? regularis , or tending towards that of P. aurigerica but does not appear to be biconcave (cf. P? heimi ) or have a depressed umbilicus (cf. P. aurigerica ). See the Species Key Chart (Appendix) for diagnostic and other characteristics.

Stratigraphic Distribution

Close to middle/late Cenomanian boundary.

So far only confidently described from the Cenomanian (unit B of the Natih Formation) of the Oman Mountains. Regarded as middle Cenomanian by Piuz & Vicedo (2020), this unit most likely contains the middle/late Cenomanian boundary ( Bromhead et al., 2022). Piuz & Vicedo (2020) regard specimens identified as Nummoloculina regularis by Afghah et al. (2014) from the Sarvak Formation of the Iranian Zagros as possibly attributable to this species. This occurrence, if valid, might be middle Cenomanian in age but requires a complete re-evaluation of the associated microfauna ( Schlagintweit & Simmons, 2022). Dr Felix Schlagintweit (pers.comm., 2023) believes he has specimens of this species from the Sarvak Formation.

Cenomanian Paleogeographic Distribution

Arabian Plate.

So far described only from the Cenomanian of the Oman Mountains and the Iranian Zagros ( Piuz & Vicedo, 2020 and Dr Felix Schlagintweit pers. comm., 2023).