Siphopfenderina Gen. Nov. (Type-Species Arenobulimina Geyikensis Solak, 2022), a Primitive Pfenderinid Foraminifera From the Cretaceous of Neotethys

A key but challenging task for biostratigraphers is to provide a biozonal/bioevent framework for geological correlation. Species of Larger Benthic Foraminifera (LBF) are important biostratigraphic markers in depositional environments where classical biostratigraphic fossils such as planktonic micro- and macrofossils are rare or absent – e.g., tropical-subtropical shallow water platforms. However, a lack of taxonomic rigour in identifying some LBF species, together with a lack of good age-calibration of their occurrences, has given rise to artificially extended biostratigraphic and paleogeographic ranges for many taxa, diluting their usefulness. In this study, the occurrences of Cenomanian LBF belonging to a “planispiral morphogroup”, both agglutinated and calcareous, have been critically evaluated to determine (i) identity; (ii) stratigraphic range; and (iii) palaeogeographic distribution. Since the last major review of the group in 1985, a voluminous literature has appeared reporting occurrences and adding new taxa. An extensive review of some 600+ published items on Cenomanian planispiral LBF – mostly published after 1985 – and a critical review of the confidence in species identification and age-calibrations therein, has led us to identify 39 taxa (three in “open” status) which appear to have distinct identity. The vast majority of these records are from Neotethys although some also occur in (or are endemic to) the Caribbean/West Atlantic and the Eastern Pacific. The quality of the published taxonomic data is variable and many published records based on identity can be discounted or termed “unconfirmed”. Likewise, many records (confirmed or otherwise) are poorly age-calibrated due to lack of corroborating biostratigraphy or chemostratigraphy, or by using circular reasoning. We summarise and illustrate the main defining characteristics of each taxon and their possible confusion species, including new taxa described since the mid-1980s. We publish new, more confident, age-ranges for these taxa – confirmed by identity and/or age-calibration – and identify where published range data may be unreliable. Paleogeographic distribution maps for each taxon are also provided. Particular stratigraphic issues around the Cenomanian- Turonian boundary are observed due to the difficulty of identifying that boundary, or its preservation, in shallow marine carbonate settings. Although most Cenomanian planispiral LBF are somewhat long-ranging, an increase in diversity throughout the middle – late Cenomanian has shown potential for biostratigraphic resolution to at least substage level using this group. Integration of the planispiral taxa with other LBF morphogroups, after similar treatment, will yield even higher biostratigraphic resolution of Cenomanian LBF and provide a sound basis for biozonation (both local and global), correlation, and age calibration.

“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

Simmons¹,

Bidgood²

2023

Challenges in Orbitolinid Identification and Biostratigraphic Consequences: An Aptian Example

SCHLAGINTWEIT

2024

The much-cited importance of Orbitolinidae in biostratigraphy depends on the species and time-interval under consideration. In any case, correct species identification is of primary importance as the basis for drawing conclusions. This task is best achieved in an assemblage where centered sections (axial and transverse) showing all details of the complex megalospheric embryo are available. Difficulties in the correct interpretation of oblique sections is exemplified by an example from the Aptian of Turkey, respectively Praeorbitolina versus Mesorbitolina. Resulting differences in species determination not only has an impact on age interpretation, but also associated geologic-tectonic conclusions, as well as basic taxonomic data (e.g., stratigraphic ranges, statistics on stage diversities).

A Review of the Identity and Biostratigraphy of Cenomanian “Larger” Benthic Foraminifera: Part 1 – The Nezzazatoidea

Simmons,

Bidgood,

Consorti

et al. 2024

The Nezzazatoidea (“nezzazatoids” herein) is a superfamily of “larger” benthic foraminifera (LBF) that are common in the Cretaceous (especially mid-Cretaceous) neritic carbonate successions of Neotethys. They are encountered in suitable rocks in a broad belt centred around Central America, the Mediterranean region, the Middle East, and the Himalayas. To improve their stratigraphic utility, the identities and distribution of 15 species are critically reviewed based on published records, these taxa having at least possible occurrences in Cenomanian strata. It is shown that misidentifications have erroneously overextended the ranges of some taxa. However, there are indeed species that have long ranges, suggesting some nezzazatoids form part of a group of environmentally tolerant LBF that were able to recover from palaeoceanographic events such as widespread anoxia or sea-level change. Some of these taxa have short ranges within the Cenomanian that mark them out as potential species to be used, alongside species from other LBF groups, in the development of a biozonation/bioevent scheme for Cenomanian LBF. As with almost all mid-Cretaceous LBF, work on taxonomy/identity of nezzazatoids is an ongoing task requiring access to pristine material, including topotypes.