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Despite making up one of the most ecologically diverse groups of living birds, comprising soaring, diving and giant flightless taxa, the evolutionary relationships and ecological evolution of Anseriformes (waterfowl) remain unresolved. Although Anseriformes have a comparatively rich, global Cretaceous and Paleogene fossil record, morphological datasets for this group that include extinct taxa report conflicting relationships for all known extinct taxa. Correct placement of extinct taxa is necessary to understand whether ancestral anseriform feeding ecology was more terrestrial or one of a set of diverse aquatic ecologies and to better understand avian evolution around the K-T boundary. Here, we present a new morphological dataset for Anseriformes that includes more extant and extinct taxa than any previous anseriform-focused dataset and describe a new anseriform species from the early Eocene Green River Formation of North America. The new taxon has a mediolaterally narrow bill which is rarely found in previously described anseriform fossils. The matrix created to assess the placement of this taxon comprises 41 taxa and 719 discrete morphological characters describing skeletal morphology, musculature, syringeal morphology, ecology, and behavior. We additionally combine the morphological dataset with published sequences using Bayesian methods and perform ancestral state reconstruction for select morphological, ecological and behavioral characters. We recover the new Eocene taxon as the sister taxon to (Anseranatidae+Anatidae) across all analyses, and find that the new taxon represents a novel ecology within known Anseriformes and the Green River taxa. Results provide insight into avian evolution during and following the K-Pg mass extinction and indicate that Anseriformes were likely ancestrally aquatic herbivores with rhamphothecal lamellae.. [ABSTRACT FROM AUTHOR]

Palaeontologists have long sought to explain the diversification of individual clades to whole biotas at global scales. Advances in our understanding of the spatial distribution of the fossil record through geological time, however, has demonstrated that global trends in biodiversity were a mosaic of regionally heterogeneous diversification processes. Drivers of diversification must presumably have also displayed regional variation to produce the spatial disparities observed in past taxonomic richness. Here, we analyse the fossil record of ammonoids, pelagic shelled cephalopods, through the Late Cretaceous, characterised by some palaeontologists as an interval of biotic decline prior to their total extinction at the Cretaceous-Paleogene boundary. We regionally subdivide this record to eliminate the impacts of spatial sampling biases and infer regional origination and extinction rates corrected for temporal sampling biases using Bayesian methods. We then model these rates using biotic and abiotic drivers commonly inferred to influence diversification. Ammonoid diversification dynamics and responses to this common set of diversity drivers were regionally heterogeneous, do not support ecological decline, and demonstrate that their global diversification signal is influenced by spatial disparities in sampling effort. These results call into question the feasibility of seeking drivers of diversity at global scales in the fossil record. Global trends in biodiversity are subject to regionally heterogeneous diversification processes. Here, the authors examine Late Cretaceous ammonoids, modelling the impact of sampling bias and potential biotic and abiotic drivers on our understanding of their biodiversity trends towards the Cretaceous-Paleogene boundary. [ABSTRACT FROM AUTHOR]

A silicite horizon corresponding to the global catastrophic event at the Cretaceous–Paleogene boundary was found for the first time in the flysch sequence of the Shapsug section on the southern slope of the Northwest Caucasus. Assemblages of radiolarians and planktonic foraminifers dating the host beds were identified. Mineralogical and analytical data support the presence of tectites, impact minerals, and increased iridium content in the boundary bed of the studied section. [ABSTRACT FROM AUTHOR]

This study reports elasmobranch remains from two fossil‐rich horizons in the earliest Danian Olching Formation at Waidach, Austria. These outer neritic assemblages complement previous fine‐scale bulk‐sampling of latest Maastrichtian horizons at Waidach and document a regional elasmobranch faunal turnover across the Cretaceous–Palaeogene (K–Pg) boundary. The Danian assemblages show homogeneity in species richness and are dominated by squaliforms. The fauna comprises 16 species belonging to 12 genera including several new taxa (Centrodeania rugosa gen. et sp. nov., Centrodeania annae gen. et sp. nov., Incognitorapax fernsebneri gen. et sp. nov., Scyliorhinus alaformis sp. nov.). Comparison with latest Maastrichtian assemblages from Waidach revealed a marked faunal turnover across the K–Pg boundary associated with an increase in species richness and shift in abundance from Squaliformes to Carcharhiniformes. This is associated with marked environmental changes from a deep marine, dysoxic setting in the Maastrichtian to a more oxygenated, shallower environment in the earliest Danian. The turnover was driven by environmentally induced regional changes in species geographic ranges. High diversity in the Danian fauna suggests that the habitability of the corresponding palaeoenvironment was preserved or recovered immediately after the K–Pg event. Comparison with other elasmobranch assemblages across the K–Pg boundary highlights a strong control of local palaeoenvironmental settings over the timing and magnitude of the turnover. Our study emphasizes the importance of successive sampling to disentangle local from general patterns of faunal turnover during the K–Pg event and to better assess the consequences of this extinction event over elasmobranch diversity. [ABSTRACT FROM AUTHOR]