Abstract

We revisit recently described putative anseriform birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). Phylogenetically relevant skeletal elements of Danielsavis nazensis Houde et al., 2023 are reported that were omitted from the original description, including the pterygoids and palatines. We detail that anseriform affinities of D. nazensis are not strongly supported and that the species shares presumably derived characteristics with the Galliformes. Actually, it is not straightforward to determine whether Danielsavis is a galliform-like stem group anseriform or whether it represents an anseriform-like stem group galliform, and our re-analysis of an emended data matrix from the original description supported galliform affinities. If D. nazensis is an anseriform bird, it is the phylogenetically earliest-diverging currently known, and in view of its morphological distinctness, the species is here assigned to a new taxon (Danielsavidae, fam. nov.). Among the material that was previously likened to Danielsavis are various fossils, which are not from galloanserine birds. Some of these have cervical vertebrae with an unusual tuberculate surface and are assigned to Perplexicervix Mayr, 2010, within the new taxon Perplexicervicidae, fam. nov. A new species, P. paucituberculata, is described and postcranial elements that are tentatively referred to this species show a resemblance to the Otidiformes (bustards). If a classification into the Otidiformes is corroborated by future studies, the fossils would constitute the first formally described Paleogene record of this Old World group of birds.