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We describe nearly complete skeletons of basal Anseriformes from the Latest Paleocene to the early Eocene of North America and Europe. Collectively, these birds appear to be representative of anseriforms near the divergence of Anhimae and Anseres, but their exact positions relative to these clades remains uncertain. A new family, Anachronornithidae nov. fam., is erected on the basis of one of these, Anachronornis anhimops nov. gen., nov. gen. et sp., to which the others cannot be confidently assigned. The new fossils augment a growing collection of early Pan-Anseriformes, which in their diversity do not paint an unambiguous picture of phylogeny or character state evolution on the path to or within crown-Anseriformes. Anachronornis nov. gen. is similar in some aspects of both cranial and postcranial anatomy to other well-represented early Paleogene Anseriformes and members of Anseres, such as Presbyornis Wetmore, 1926. However, it exhibits a more landfowl-like bill, like that of Anhimae and unlike the spatulate bill of Anseres. Additional specimens of similar basal Anseriformes of uncertain affinities from the early Eocene of North America and Europe further complicate interpretation of character state polarity due to the mosaicism of primitive and derived characters they exhibit. [ABSTRACT FROM AUTHOR]

In contrast to the rich collections of articulated spiny-rayed fishes from early Late Cretaceous and Eocene Lagerstätten, similar skeletal remains are sparse in Maastrichtian-Paleocene strata. Here we coin this poorly understood span "Patterson's Gap" and review known articulated skeletons from it, summarizing available information on their phylogenetic affinities, age, and environmental context. Roughly fifty percent of taxa in both the Maastrichtian and Paleocene come from Europe and North America, with percomorphs representing around 60% of the skeletal acanthomorph taxa in each interval. This is higher than the only pre-Maastrichtian assemblage with a reasonable sample of percomorphs, but lower than most Eocene and younger sites. Fossils from Patterson's Gap show a steady accumulation of the principal lineages of spiny-rayed fishes. Material from Paleocene or older strata provides evidence for most of the roughly 20 major acanthomorph divisions recovered by molecular studies. Many fossils from Patterson's Gap remain undescribed and unnamed, and almost none have been included within formal phylogenetic analyses. Revision of existing material, combined with additional fieldwork, should be a priority for future efforts seeking to clarify this murky but significant interval in the evolutionary history of a major vertebrate radiation. [ABSTRACT FROM AUTHOR]

Metatherian mammals were the most diverse mammalian clade in North America through the Late Cretaceous, but they underwent a severe extinction at the Cretaceous–Palaeogene (K-Pg) boundary. In order to clarify the origin of Palaeogene metatherians and the pattern of metatherian survivorship across the K-Pg boundary we conducted an inclusive species-level phylogenetic analysis of Cretaceous and early Palaeogene metatherian taxa. This analysis includes information from new Palaeocene specimens from south-western North America. Both the phylogenetic topology and information from new specimens support the validity of the genus Thylacodon and justify the recognition of a new species, T. montanensis. Thylacodon is closely related to Swaindelphys and Herpetotheriidae, which must have diverged by the latest Cretaceous due to its close relationship with late Campanian Ectocentrocristus. Pediomyidae and ‘Peradectidae sensu lato’ together comprise a major metatherian clade. Maastrichtidelphys, from the Late Cretaceous of the Netherlands, is the oldest member of ‘Peradectidae sensu lato’, indicating a Cretaceous origination for this group. Therefore, the major groups Herpetotheriidae and ‘Peradectidae sensu lato’, represented almost completely by Palaeocene taxa, must have originated in the Late Cretaceous. The lineages leading to these clades include at least four lineages that must have crossed the K-Pg boundary and therefore confirm that the K-Pg boundary marked a profound extinction event for metatherians and suggests that Palaeogene taxa originated from only a few clades of Cretaceous species, all of which were relatively minor or very rare components of known Cretaceous mammalian faunas. [ABSTRACT FROM PUBLISHER]