Nummoloculinodonta akhdarensis Piuz & Vicedo, 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 : 104

Nummoloculinodonta akhdarensis Piuz & Vicedo, 2020

Reference Illustration & Description

Piuz & Vicedo (2020), fig. 4(A-I) & fig. 5(A-AB), p. 13- 14.

Originally described and recorded from the Cenomanian Natih Formation of the Oman Mountains. Piuz & Vicedo (2020) remark that the complex apertural features of this genus are still poorly understood (although a tooth seems to be present) and are seldom visible in random this sections. N. akhdarensis appears to be characterised by a well-developed milioline (mostly quinqueloculine) nepionic stage of up to 6 whorls followed by an adult planispiral stage which coils in another plane. This adult stage can show up to 4 whorls with a maximum of 4 chambers per whorl. Apertural notches/ribs are seen in the later (gerontic) stage and pillars or pillar-like structures can also be seen. The overall shape is probably the most broadly rounded biconvex or globular of all the Albian-Turonian ‘nummoloculinids’ though can approach an axial profile similar to that of Pseudonummoloculina aurigerica . See the Species Key Chart (Appendix) for diagnostic and other characteristics.

This new genus differs from Pseudonummoloculina in the posession of an apertural tooth and a general absence (except in gerontic forms) of apertural crenulations. However, Piuz & Vicedo (2020) also admit that the genus may correspond partially to the (invalid) genus Nummoloculina emend. Conkin & Conkin (1958) and that more work on the nature of the aperture is required.

N. akhdarensis differs from P. aurigerica in being somewhat more globular, by posessing an aperture with a complex tooth, fewer chambers (maximum 4 cf. 6-8) and posessing notches only within the last (gerontic) stage of development.

Stratigraphic Distribution

(Barremian) early -?middle Cenomanian (Santonian).

The type material is from unit E of the Natih Formation of the Oman Mountains ( Piuz & Vicedo, 2020). This is most likely early Cenomanian in age ( Bromhead et al., 2022), although extension into the middle Cenomanian cannot be completely excluded. However, Piuz & Vicedo (2020) include the following published occurrences in possible/probable synonymy with N. akhdarensis . These attributions are tentative as not all diagnostic details are visible:

Nummoloculina sp. in Arnaud-Vanneau (1980), France, which is recorded as Barremian in age.

Nummoloculina sp. in Arnaud-Vanneau & Darsac (1984), France, recorded as Barremian – Aptian in age.

Pseudonummoloculina n. sp. indet. in Hottinger et al. (1989), Mexico, recorded as late Santonian in age.

Pseudonummoloculina sp. cf. N. heimi in De Castro (1987) , Italy, recorded as Cenomanian in age.

Pseudonummoloculina sp. in Radoičić (1994), the Balkans, recorded as late Cenomanian in age.

Pseudonummoloculina heimi in Hottinger et al. (1989), Mexico, recorded as Cenomanian in age.

If confirmed, these would greatly extend the range of the species. However herein, only the confirmed range is shown.

Cenomanian Paleogeographic Distribution

(Caribbean/Neotethys?) Arabian Plate.

Confirmed Cenomanian occurrences are restricted to the type description from the Oman Mountains ( Piuz & Vicedo, 2020) but possible occurrences are recorded from Mexico, Italy, and the Balkans (see references above). Revisions to P.? ex. grp. heimi (see above) may extend the distribution further.