DOI: 10.5061/dryad.n02v6wx3k
title: Cretaceous Antarctic bird skull elucidates early avian ecological diversity

description: 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, and the mandible lacked retroarticular processes.
 Together, these features comprise a feeding apparatus unlike any other
 known anseriform but like extant birds that capture prey underwater (e.g.,
 grebes, loons). The Cretaceous occurrence of Vegavis, with a feeding
 ecology unique among known extant Galloanserae (water- and landfowl), is
 further indication that the earliest anseriform divergences were marked by
 evolutionary experiments unrepresented in the extant diversity.
description: See main text and supplemental information.
description: # 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 in plain text format; readable by any
 text editor. .TRE files contain topological and (for MrBayes analyses)
 branch length data pertaining to the phylogenetic trees produced by
 phylogenetic analyses in nexus format. .CKP files contain checkpoint
 information from MrBayes analyses in nexus format. .LSTAT files contain
 marginal likelihoods estimated during MrBayes analyses in tab delimited
 text format.  .MCMC files contain run diagnostics from MrBayes analyses in
 tab delimited text format. .PARTS files contain tables of taxon
 bipartitions from MrBayes analyses in tab delimited text format. .TSTAT
 files contain summary statistics pertaining to the taxonomy bipartitions
 from MrBayes in tab delimited format. .PSTAT files contain parameter
 values for MrBayes analyses in tab delimited text format. .P files contain
 parameters for substitution models used in MrBayes analyses in tab
 delimited text files. .T and .TRPROBS files contain the topology and
 branch length data estimated by MrBayes analyses in nexus format. .VSTAT
 files contain statistics pertaining to branch and node parameters
 estimated by MrBayes analyses in tab delimited text format. Phylogenetic
 trees contained in nexus files are viewable using the freely available
 FigTree software (tree.bio.ed.ac.uk/software/figtree/). * **Subfolders
 SD02a-j** - outputs from our phylogenetic analyses using the character
 matrix focused on resolving relationships among Avialae (i.e.,
 SD01_Avialae_matrix.nex): * **SD02a** - PAUP analysis, including only
 previously-described Vegavis material (Extended Data Fig. 6d) * **SD02b**
 - MrBayes analysis, including only previously-described Vegavis material
 (Extended Data Fig. 6c) * **SD02c** - PAUP analysis, including only the
 new Vegavis specimen (Extended Data Fig. 6f) * **SD02d** - MrBayes
 analysis, including only the new Vegavis specimen (Extended Data Fig. 6e)
 * **SD02e** - PAUP analysis, including both previously-described and the
 new Vegavis specimen as separate tips (Extended Data Fig. 6h) * **SD02f**
 - MrBayes analysis, including both previously-described and the new
 Vegavis specimen as separate tips (Extended Data Fig. 6g) * **SD02g** -
 PAUP analysis, including both previously-described and the new Vegavis
 specimen as a combined tip (Extended Data Fig. 6b) * **SD02h** - MrBayes
 analysis, including both previously-described and the new Vegavis specimen
 as a combined tip (Extended Data Fig. 6a) * **SD02i** - PAUP analysis,
 including both previously-described and the new Vegavis specimen as a
 combined tip and including Gansus yumenensis (Extended Data Fig. 6i) *
 **SD02j** - MrBayes analysis, including both previously-described and the
 new Vegavis specimen as a combined tip and including Gansus yumenensis
 (Extended Data Fig. 6j) - **Subfolders SD02k-r** - outputs from our
 phylogenetic analyses using the character matrix focused on resolving
 relationships among Galloanserae (i.e., SD03_Galloanserae_matrix.nex) with
 the taxon Anachronornis excluded: * **SD02k** - PAUP analysis, including
 only previously-described Vegavis material (Extended Data Fig. 6d) *
 **SD02l** - MrBayes analysis, including only previously-described Vegavis
 material (Extended Data Fig. 6c) * **SD02m** - PAUP analysis, including
 only the new Vegavis specimen (Extended Data Fig. 6f) * **SD02n** -
 MrBayes analysis, including only the new Vegavis specimen (Extended Data
 Fig. 6e) * **SD02o** - PAUP analysis, including both previously-described
 and the new Vegavis specimen as separate tips (Extended Data Fig. 6h) *
 **SD02p** - MrBayes analysis, including both previously-described and the
 new Vegavis specimen as separate tips (Extended Data Fig. 6g * **SD02q** -
 PAUP analysis, including both previously-described and the new Vegavis
 specimen as a combined tip (Extended Data Fig. 6a) * **SD02r** - MrBayes
 analysis, including both previously-described and the new Vegavis specimen
 as a combined tip (Extended Data Fig. 6b) * **Subfolders SD02s-z** -
 outputs from our phylogenetic analyses using the character matrix focused
 on resolving relationships among Galloanserae (i.e.,
 SD03_Galloanserae_matrix.nex) with the taxon Anachronornis included: *
 **SD02s** - PAUP analysis, including only previously-described Vegavis
 material (Extended Data Fig. 6l) * **SD02t** - MrBayes analysis, including
 only previously-described Vegavis material (Extended Data Fig. 6k) *
 **SD02u** - PAUP analysis, including only the new Vegavis specimen
 (Extended Data Fig. 6n) * **SD02v** - MrBayes analysis, including only the
 new Vegavis specimen (Extended Data Fig. 6m) * **SD02w** - PAUP analysis,
 including both previously-described and the new Vegavis specimen as
 separate tips (Extended Data Fig. 6p) * **SD02x** - MrBayes analysis,
 including both previously-described and the new Vegavis specimen as
 separate tips (Extended Data Fig. 6o) * **SD02y** - PAUP analysis,
 including both previously-described and the new Vegavis specimen as a
 combined tip (Extended Data Fig. 6j) * **SD02z** - MrBayes analysis,
 including both previously-described and the new Vegavis specimen as a
 combined tip (Extended Data Fig. 6i) **SD03_Galloanserae_matrix.nex** -
 Our morphological character matrix in Nexus format (.NEX) focused on
 Galloanserae 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)).
 **SD04_scan_data_volume_details.csv** - Details about how the positions of
 the CT scan datasets used in this study were transformed/rotated for
 alignment to a reference CT scan dataset (i.e., the 2018 scan of Block A
 of AMNH FARB 30899). See Supplemental Information for how we aligned these
 datasets. Columns: * SCAN REFERENCE - the name of the CT scan dataset
 being transformed * MORPHOSOURCE VOLUME FILE MEDIA ID - the ID number
 corresponding to the CT scan dataset on
 [www.MorphoSource.org](http://www.MorphoSource.org) * MORPHOSOURCE MEDIA
 URL - the URL address for the CT scan dataset on
 [www.MorphoSource.org](http://www.MorphoSource.org) * TRANSLATION X -
 translational adjustment along the X axis (in mm) * TRANSLATION Y -
 translational adjustment along the Y axis (in mm) * TRANSLATION X -
 translational adjustment along the Z axis (in mm) * ROTATIONAL DEGREES -
 total rotation (in degrees) * ROTATION X - rotational adjustment about the
 X axis (in degrees) * ROTATION Y - rotational adjustment about the Y axis
 (in degrees) * ROTATION Z - rotational adjustment about the Z axis (in
 degrees) **SD05_polygon_details.csv** - Details about how the positions of
 mesh files corresponding to independent skeletal elements (included in
 SD08_surface_files_full_reconstruction.zip) were adjusted for alignment to
 the reference CT scan dataset (i.e., the 2018 scan of Block A of AMNH FARB
 30899). Columns: * POLYGON REFERENCE - the element being transformed *
 CATEGORY - the type of element being transformed (Bone = skeletal element;
 Impression or Void = negative space corresponding to inferred skeletal
 element; Matrix = non-skeletal region of the dataset corresponding to
 rock) * MORPHOSOURCE MEDIA ID - the ID number corresponding to the CT scan
 dataset on [www.MorphoSource.org](http://www.MorphoSource.org) *
 MORPHOSOURCE MEDIA URL - the URL address for the CT scan dataset on
 [www.MorphoSource.org](http://www.MorphoSource.org) * VOLUME FILE
 REFERENCE - the CT scan dataset from which the mesh file was derived *
 LABEL FILE REFERENCE - the label file derived from the CT scan dataset
 that includes the mesh file * SMOOTHING PROTOCOL - the settings in the
 segmentation editing software Avizo (FEI) used when smoothing the surface
 contour of the mesh * TRANSLATION X - translational adjustment along the X
 axis (in mm) * TRANSLATION Y - translational adjustment along the Y axis
 (in mm) * TRANSLATION X - translational adjustment along the Z axis (in
 mm) * ROTATIONAL DEGREES - total rotation (in degrees) * ROTATION X -
 rotational adjustment about the X axis (in degrees) * ROTATION Y -
 rotational adjustment about the Y axis (in degrees) * ROTATION Z -
 rotational adjustment about the Z axis (in degrees)
 **SD06_taphonomic_data_reconstruction.mp4** - A video file cut-through of
 our 3D realignment of scan data showing a, uCT XY slice reconstruction of
 the 2014 Block A and Block B data in unified coordinate space, and b,
 slice reconstruction with polygons of segmented cranial elements. Scale
 bars = 2 cm. **SD07_taphonomic_reconstruction.pdf** - 3D PDF of realigned
 CT scan data and surface files (see Supplemental Information).
 **SD08_surface_files_original_material_only.zip** - Compressed folder of
 polygon files (.PLY) of only originally preserved elements (Fig. 1,
 Extended Data Figs. 2-4). Spatial positioning is preserved relative to
 surface files in SD09_surface_files_full_reconstruction.zip. Files can be
 opened using the open source program Meshlab (https://www.meshlab.net).
 **SD09_surface_files_full_reconstruction.zip** - Compressed folder of
 polygon files (.PLY) of reconstructed skull with mirrored elements
 (Extended Data Fig. 5) Spatial positioning is preserved relative to
 surface files in SD08_surface_files_original_material_only.zip. Files can
 be opened using the open source program Meshlab (https://www.meshlab.net).
 **SD10_original_material.blend** - A Blender file of only originally
 preserved elements (Fig. 1, Extended Data Figs. 2-4). Blender is a free,
 open-source program that can be downloaded at
 [https://www.blender.org](https://www.blender.org).
 **SD11_retro_deformation.blend** - A Blender file of reconstructed skull
 with mirrored elements (Extended Data Fig. 5). Blender is a free,
 open-source program that can be downloaded at
 [https://www.blender.org](https://www.blender.org). ### Sharing/Access
 Information Related data are available on MorphoSource
 ([https://www.morphosource.org/concern/biological_specimens/000553312](https://www.morphosource.org/concern/biological_specimens/000553312))