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Vegaviidae; Temporal range: Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N Uncertain Campanian and Paleocene records
	Life restoration of Vegavis iaai
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	†Vegaviiformes; Worthy et al., 2017
Family:	†Vegaviidae; Agnolín et al., 2017
Genera
	†Antarcticavis?; †Australornis?; †Maaqwi?; †Neogaeornis?; †Polarornis; †Vegavis;

Vegaviidae is an extinct family of birds of uncertain phylogenetic placement, which existed during the Late Cretaceous and possibly the Paleocene. Definitive fossils attributed to the family have only been found in Antarctica, though other fossils from the Southern Hemisphere including Chile and New Zealand may represent this group.^[1]^[2] The putative Campanian vegaviid from Canada known as Maaqwi,^[3] more likely belongs to the Procellariformes.^[2]

Previously the genera Neogaeornis and Polarornis were classified as stem-loons based on the similarities in the anatomy of the leg structure.^[4]^[5]^[6] However, there were some criticism to these assertions as the material are from incomplete specimens from Antarctica lacking several important loon characteristics.^[7]^[8]

In 2017 Agnolín and colleagues performed a phylogenetic analysis of these genera in addition to the newly discovered Australornis and Vegavis, the latter genus of which a more complete specimen had been found.^[9] This allowed the team to do anatomical comparisons between these genera.^[1] They found support for them making up a family of birds showing specializations to diving, classified as the sister taxon to crown Anseriformes.^[1] This was interpreted as evidence that some families of modern birds crossed the K–Pg boundary unaffected by the extinction event that occurred.^[1] The authors also stated this is further evidence of Gondwana having an important role for the evolution of modern birds.^[1]

Another 2017 paper by Worthy et al. focusing on the evolution and phylogenetic relationships of giant fowl found weak support for Vegaviidae being the sister taxon to Gastornithiformes (the clade including Gastornithidae and the mihirungs).^[10] The description and phylogenetic placement of Maaqwi by McLachlan et al. (2017) found an alternative position for vegaviids as stem-birds in the more inclusive clade Ornithurae.^[3]

Mayr et al. (2018) did a review of vegaviid systematics stating that while Vegavis and Polarornis are likely sister genera based on overall similarities in their femur and tibiotarsal bones, the inclusion of other taxa, particularly Australornis, is poorly supported.^[11] Furthermore, they argued that comparison of the plesiomorphic traits of the pterygoid and the mandible does not seem to firmly establish anseriform or galloanserine affinities for Vegaviidae, and commented that to try to classify all southern hemisphere birds into a single clade is premature as it may not illustrate the complex relationships and the convergent evolution birds have undergone.^[11] He also suggested that it is uncertain whether Neogaeornis belongs to the family since the specimen shows traits of other bird groups including those of podicipediform and gaviiform,^[11] but if it were true, then both Neogaeornis and possibly the closely related Antarcticavis might represent vegaviids.^[2]

Field et al. (2020) considered Vegavis to be either a sister taxon to the Neornithes outside the crown group birds, or as a taxon at the base of Neognathae with an unresolved position.^[12] While other researchers have recovered Vegavis as a neornithine, they did not consider it to be a member of Anseriformes or Galloanserae, since they cannot find any diagnostic traits of those clades.^[13]^[14] In contrast, Vegavis was recovered as a sister taxon of Anatidae or Anseriformes based on phylogenetic analyses in 2024.^[15]^[16]

References

^ ^a ^b ^c ^d ^e Agnolín, F.L.; Egli, F.B.; Chatterjee, S.; Marsà, J.A.G (2017). "Vegaviidae, a new clade of southern diving birds that survived the K/T boundary". The Science of Nature. 104 (87): 87. Bibcode:2017SciNa.104...87A. doi:10.1007/s00114-017-1508-y. PMID 28988276. S2CID 13246547.
^ ^a ^b ^c Mayr, G. (2022). "Basic Terminology and the Broader Phylogenetic and Geological Framework)". Paleogene Fossil Birds. Springer Cham. pp. 3–27. doi:10.1007/978-3-030-87645-6_2.
^ ^a ^b Sandy M. S. McLachlan; Gary W. Kaiser; Nicholas R. Longrich (2017). "Maaqwi cascadensis: A large, marine diving bird (Avialae: Ornithurae) from the Upper Cretaceous of British Columbia, Canada". PLOS ONE. 12 (12): e0189473. Bibcode:2017PLoSO..1289473M. doi:10.1371/journal.pone.0189473. PMC 5722380. PMID 29220405.
^ Olson, S (1992). "Neogaeornis wetzeli Lambrecht, a Cretaceous loon from Chile (Aves, Gaviidae)". Journal of Vertebrate Paleontology. 12 (1): 122–124. doi:10.1080/02724634.1992.10011438.
^ Hope, S. (2002). "The Mesozoic radiation of Neornithes." Pp. 339-388 in Chiappe, L.M. and Witmer, L. (eds.), Mesozoic Birds: Above the Heads of Dinosaurs.
^ Carolina Acosta Hospitaleche, Javier N. Gelfo, New Antarctic findings of Upper Cretaceous and lower Eocene loons (Aves: Gaviiformes), Annales de Paléontologie Volume 101, Issue 4, October–December 2015, Pages 315–324
^ Feduccia, A. (1999). The Origin and Evolution of Birds. 2nd edition. Yale University Press.
^ Mayr, G (2004). "A partial skeleton of a new fossil loon (Aves, Gaviiformes) from the early Oligocene of Germany with preserved stomach content" (PDF). Journal of Ornithology. 145 (4): 281–286. doi:10.1007/s10336-004-0050-9. S2CID 1070943.
^ Clarke, J.A.; Chatterjee, S.; Li, Z.; Riede, T.; Agnolin, F.; Goller, F.; Isasi, M.P.; Martinioni, D.R.; Mussel, F.J.; Novas, F.E. (2016). "Fossil evidence of the avian vocal organ from the Mesozoic". Nature. 538 (7626): 502–505. Bibcode:2016Natur.538..502C. doi:10.1038/nature19852. PMID 27732575. S2CID 4389926.
^ Worthy, T.H.; Degrange, F.J.; Handley, W.D.; Lee, M.S.Y. (2017). "The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)". Royal Society Open Science. 11 (10): 170975. Bibcode:2017RSOS....470975W. doi:10.1098/rsos.170975. PMC 5666277. PMID 29134094.
^ ^a ^b ^c Mayr, G.; De Pietri, V.L.; Scofield, R.P.; Worthy, T.H. (2018). "On the taxonomic composition and phylogenetic affinities of the recently proposed clade Vegaviidae Agnolín et al., 2017 ‒ neornithine birds from the Upper Cretaceous of the Southern Hemisphere)". Cretaceous Research. 86: 178–185. doi:10.1016/j.cretres.2018.02.013. hdl:2328/37887. S2CID 134876425.
^ Field, Daniel J.; Benito, Juan; Chen, Albert; Jagt, John W. M.; Ksepka, Daniel T. (18 March 2020). "Late Cretaceous neornithine from Europe illuminates the origins of crown birds". Nature. 579 (7799): 397–401. doi:10.1038/s41586-020-2096-0. ISSN 1476-4687. PMID 32188952. S2CID 212937591.
^ Acosta Hospitaleche C, Worthy TH (2021). "New data on the Vegavis iaai holotype from the Maastrichtian of Antarctica". Cretaceous Research. 124. 104818. Bibcode:2021CrRes.12404818A. doi:10.1016/j.cretres.2021.104818. S2CID 233703816.
^ Álvarez-Herrera, G. P.; Rozadilla, S.; Agnolín, F. L.; Novas, F. E. (2024). "Jaw anatomy of Vegavis iaai (Clarke et al., 2005) from the Late Cretaceous Antarctica, and its phylogenetic implications". Geobios. 83: 11–20. doi:10.1016/j.geobios.2023.03.004. S2CID 259955013.
^ Musser, G.; Clarke, J. A. (2024). "A new Paleogene fossil and a new dataset for waterfowl (Aves: Anseriformes) clarify phylogeny, ecological evolution, and avian evolution at the K-Pg Boundary". PLOS ONE. 19 (7). e0278737. doi:10.1371/journal.pone.0278737. PMC 11288464. PMID 39078833.
^ Crane, A.; Benito, J.; Chen, A.; Musser, G.; Torres, C. R.; Clarke, J. A.; Lautenschlager, S.; Ksepka, D. T.; Field, D. J. "Taphonomic damage obfuscates interpretation of the retroarticular region of the Asteriornis mandible". Geobios. doi:10.1016/j.geobios.2024.03.003.