The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)

Abstract

The extinct dromornithids, gastornithids and phorusrhacids are among the most spectacular birds to have ever lived, with some giants exceeding 500 kg. The affinities and evolution of these and other related extinct birds remain contentious, with previous phylogenetic analyses being affected by widespread convergence and limited taxon sampling. We address these problems using both parsimony and tip-dated Bayesian approaches on an expansive taxon set that includes all key extinct flightless and flighted (e.g. Vegavis and lithornithids) forms, an extensive array of extant fowl (Galloanseres), representative Neoaves and palaeognaths. The Paleogene volant Lithornithidae are recovered as stem palaeognaths in the Bayesian analyses. The Galloanseres comprise four clades inferred to have diverged in the Late Cretaceous on Gondwana. In addition to Anseriformes and Galliformes, we recognize a robust new clade (Gastornithiformes) for the giant flightless Dromornithidae (Australia) and Gastornithidae (Eurasia, North America). This clade exhibits parallels to ratite palaeognaths in that flight presumably was lost and giant size attained multiple times. A fourth clade is represented by the Cretaceous Vegavis (Antarctica), which was strongly excluded from Anseriformes; thus, a crucial molecular calibration point needs to be reconsidered. The presbyornithids Wilaru (Australia) and Presbyornis (Northern Hemisphere) are robustly found to be the sister group to Anatoidea (Anseranatidae + Anatidae), a relatively more basal position than hitherto recognized. South America's largest bird, Brontornis, is not a galloansere, but a member of Neoaves related to Cariamiformes; therefore, giant Galloanseres remain unknown from this continent. Trait analyses showed that while gigantism and flightlessness evolved repeatedly in groups, diet is constrained by phylogeny: all giant Galloanseres and palaeognaths are herbivores or mainly herbivorous, and giant neoavians are zoophagous or omnivorous.

Bayesian Tip-dated Phylogenetics: Topological Effects, Stratigraphic Fit and the Early Evolution of Mammals

“…can sometimes be misleading, a fact becoming increasingly apparent with the availability of 449 increasing amounts of molecular data (Lee and Palci 2015). Stratigraphic data provides an 450 opportunity to identify probable convergent evolution in clades widely separated by time, a point 451 that has already been demonstrated in tip-dated phylogenetic analyses of palaeognath birds 452 (Worthy et al 2017) and gharials (Lee and Yates 2018). 453…”

Total-Evidence Framework Reveals Complex Morphological Evolution in Nightbirds (Strisores)

“…Mayr [2] previously noted that few osteological similarities are shared between Steatornithidae and Nyctibiidae, despite recent molecular analyses suggesting a close relationship between these two groups. In some cases, such as the absence of the distal interosseous canal of the tarsometatarsus (the sole morphological synapomorphy identified for a (Podargidae + Daedalornithes) clade), potential synapomorphies characterizing deep divergences in Strisores are also widespread among other crown-birds [2,79] and cannot be considered uniquely diagnostic of the clades recovered by our analyses. Furthermore, some synapomorphies of Strisores identified by our and previous studies (such as the very short bill and the deep transverse sulcus of the humerus) [80,81] are not present in podargids, as previously pointed out by Mayr [4].…”

The middle Miocene duck Chenoanas (Aves, Anatidae): new species, phylogeny and geographical range

“…The codings for newly‐added outgroup taxa Megapodius reinwardt and Lithornis promiscuus were prepared generally using Houde () and Worthy et al . (), but comparative skeletal collection of PIN and fossil material stored in USNM were also consulted.…”

“…We added additional primitive taxa Lithornis promiscuus and Megapodius reinwardt (see Worthy et al . ; ) in order to better polarize character states. Lithornis promiscuus was used as the outgroup.…”