Cretaceous Antarctic bird skull elucidates early avian ecological diversity

Fossils representing Cretaceous lineages of crown clade birds (Aves) are exceptionally rare but are crucial to elucidating changes in key anatomical systems across early avian divergences. Among the earliest known putative crown birds is Vegavis iaai, a foot-propelled diver from the latest Cretaceous (69.2–68.4 Ma) of Antarctica with controversial phylogenetic affinities. Initially reported as a stem anatid (ducks and closely related species), Vegavis has since been recovered as a stem member of Anseriformes (waterfowl) or outside Aves altogether. Here we report a new, nearly complete skull of Vegavis that preserves novel information on its feeding ecology and phylogenetic affinities. Vegavis exhibits a definitively avian beak (absence of teeth, reduced maxilla) and brain shape (hyperinflated cerebrum, ventrally shifted optic lobes). The temporal fossa is well excavated and expansive, indicating that this bird had hypertrophied jaw musculature. The beak was narrow and pointed,..., See main text and supplemental information., , # Cretaceous Antarctic bird skull elucidates early avian ecological diversity

Christopher R. Torres, Julia A. Clarke, Joseph R. Groenke, Matthew C. Lamanna, Ross D. E. MacPhee, Grace M. Musser, Eric M. Roberts & Patrick M. O'Connor. 2025. Nature 638 146-151.

This package includes our phylogenetic character matrices and the results of our phylogenetic analyses (SD01-SD03), details about how CT scan data were collected (SD04), and files derived from CT scan data (SD05-SD11).

### Contents

**SD01_Avialae_matrix.nex** - Our morphological character matrix in Nexus format (.NEX) focused on Avialae with PAUP and BAYES command blocks (see Supplemental Information for character descriptions). .NEX files can be viewed in a text editor or the Mesquite software ([www.mesquiteproject.org](http://www.mesquiteproject.org)).

**SD02_phylogenetic_analyses_outputs.zip** - Compressed folder of files output from our phylogenetic analyses. File types within: .TXT files contain the logs from PAUP analyses...,