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.

Appendices include input files in nexus format (i.e., data matrices, executable commands, and constraint trees) for phylogenetic parsimony analysis (including bootstrap) and Kishino-Hasegawa tests in PAUP and Bayesian phylogenetic anlysis in MrBayes. Appendices also include output files (i.e., results) of these analyses and .tre files that can be opened with Figtree. Also included are Appendices of shared characters and apomorphies for each of seven datasets.

All included files can be opened with MSword or any text editor. Many of these are executable files that can be opened and run in PAUP, MrBayes, and Figtree.