| Gastornithiformes | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Superorder: | Galloanserae |
| Order: | †Gastornithiformes Stejneger, 1885 |
| Subgroups | |
Gastornithiformes are an extinct order of giant flightlessfowl with fossils found inNorth America,Eurasia, possiblyAustralia.[1] Members ofGastornithidae were long considered to be a part of the orderGruiformes. However, the traditional concept of Gruiformes has since been shown to bepolyphyletic.
Beginning in the late 1980s and the first phylogenetic analysis of gastornithid relationships, consensus began to grow that they were close relatives of the lineage that includeswaterfowl andscreamers, theAnseriformes.[2] Recognizing the apparent close relationship betweenGastornis and waterfowl, some researchers even classify them within the anseriform group itself.[3] Others restrict the name Anseriformes only to the crown group formed by all modern species, and label the larger group including extinct relatives of anseriformes in the cladeAnserimorphae (which this article and related pages have adopted).[4] While the order is generally considered to be monotypic, a 2017 paper concerning the evolution and phylogeny of giant fowl by Worthy and colleagues have found phylogenetic support in finding the mihirungs (Dromornithidae) to be the sister taxon to theGastornis.[1]
The mihirungs are also another family of giant flightless birds that have been classified as anserimorphs either as crown anseriforms closely related to the screamers (Anhimidae)[5] or the sister taxon to Anseriformes.[3] Worthy et al. (2017) incorporated several new taxa and character traits into existing matrices ofGalloanserae resulted in several of their phylogenies to support this grouping.[1] The authors did note the bootstrap support is weakly supported and one of their phylogenies even found gastornithiforms to bestem-galliforms instead.[1] These were also weakly supported.[1] Below is a simplified phylogeny showing their one phylogeny supporting gastornithiforms as anserimorphs.[1]
| Anserimorphae |
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However, McInerny et al. (2024) instead recovered mihirungs as crown-group members ofAnseriformes related to modernscreamers, while recovering gastornithids as members of theGalliformes. They also found weak support for theSylviornithidae (another enigmatic family of giant birds fromOceania that also went extinct during theQuaternary) potentially being a sister group to Gastornithidae. The lineage containing these two families was found to alternatively represent a group of stem-Galliformes, or a group of crown-group Galliformes more derived than themegapodes but basal to all other members of the group.[6]
In a 2021 paper by Agnolin found the enigmatic Argentinian genusBrontornis from theMiocene deposits, often considered to be aterror bird, found to a gastornithiform sister to the mihirungs.[7]
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