Understanding the response of calcareous nannoplankton to past environmental perturbations is critical for assessing the impact of paleoenvironmental changes on marine calcifiers. Here, we analyze the size, morphotype distribution, and abundance of Eprolithus floralis across Oceanic Anoxic Event (OAE) 2 at Clot Chevalier (SE France), Novara di Sicilia (S Italy), and Tarfaya (Morocco), and compare them with Eastbourne (UK) to distinguish supra-regional from local environmental controls.Mean total diameter differs by ∼1 μm between northern and southern sections and decreases from pre-OAE 2 to OAE 2, with minimum mean values generally reached around peak B of the carbon-isotope excursion. The magnitude of this decrease varies among sections, reflecting different regional baseline conditions. Rounded specimens are on average ∼0.58 μm smaller than spiky specimens, and their increased relative abundance during OAE 2 contributes to the observed size decrease. Specimens with lowest size (3.2–3.5 μm) are extremely rare, suggesting a possible minimum size for the species. The magnitude of the morphometric response differs among sections, with the largest size reductions during OAE 2 at Clot Chevalier (16%) and Tarfaya (10%) and most complete post-OAE 2 recovery recorded at the northern localities, which also display the largest pre-OAE 2 average size. Neither temperature nor nutrient availability explains the common morphometric evolution observed across the four localities. Instead, the temporal correspondence between volcanism, atmospheric CO2 increase and the onset, maximum size decrease and recovery, suggests that perturbations of the marine carbonate system exerted a control on coccolithophore calcification.
The Cretaceous/Paleogene boundary records one of the key events in history of life, but not all clades were affected similarly. Albanerpetontidae, an extinct group of lissamphibians, appears to have been little impacted, yet their patchy Upper Cretaceous record in Europe, concentrated in the Santonian to the Maastrichtian, limits our understanding. For the last 20 years, the Ibero-Armorican Island has been one of the key areas for studying these stages; but despite several occurrences of albanerpetontids, none has been described in detail. Here we report a new albanerpetontid species from the upper Maastrichtian Blasi 2B locality (Huesca, Spain), based on disarticulated cranial and postcranial bones. Synorerpeton ribagorzana gen. et sp. nov. represents the first formally described Upper Cretaceous European albanerpetontid species. It is characterized by the orbital margin of the frontal located anterior to the anteroposterior midpoint of the bone, subrectangular atlas cotyles, a weakly curved posterior edge of the maxillary nasal process, and a large palatal foramen in the premaxillae. The latter trait is shared with ‘Albanerpeton’ galaktion from the Campanian of North America. Synorerpeton shows affinities with other Ibero-Armorican material but differs from eastern European taxa, suggesting two distinct albanerpetontid populations coexisted during the Late Cretaceous of Europe. Our results also support that Albanerpeton is polyphyletic. We recommend restricting the genus to a subset of species containing the type species A. inexpectatum and all species more closely related to it than to ‘A.’ nexuosum; thus, containing for now only both European Cenozoic species A. inexpectatum and A. pannonicum.
