Vegavis

Vegavis is a genus of extinct bird that lived in Antarctica during the Maastrichtian stage of the Late Cretaceous, around. The type species is Vegavis iaai. Vegavis was considered to be a member of Anseriformes within Galloanserae, but this claim has not been supported by recent studies.

Taxonomy
The genus name, Vegavis, is a combination of the name of Vega Island and "avis", the Latin word for bird, while the species name, "iaai", is after the acronym for Instituto Antartico Argentino (IAA), the Argentine scientific expedition to Antarctica. The holotype is held by the Museo de La Plata, Argentina. The specimen, cataloged as MLP 93-I-3-1, was found in 1993 from the López de Bertodano Formation at Cape Lamb on Vega Island, Antarctica, and was first thought to be an indeterminate presbyornithid. It was only described as a new species in 2005, because it consists of the very delicate remains of one bird embedded in a concretion, which had to be meticulously prepared for study. CT scans were utilized to gain a clearer picture of the bone structure without running danger of damaging or destroying the fossil.

A second specimen, MACN-PV 19.748 (formerly MLP 93-I-3-2), was found beside the holotype specimen. It was preserved in three dimensions, so CT scans were again utilized to visualize the intact syrinx of this specimen. The syrinx has an asymmetrical third segment, suggesting that Vegavis had two sources of sound in the neck and along with large soft-tissue resonating structures. This indicates that it was likely capable of honks as in ducks, geese, and other basal neognaths.

Classification
Vegavis has been previously thought to be a member of the stem-group Anseriformes within Galloanserae, indicating that representatives of some of the groups of modern birds lived in the Mesozoic. However, many paleontologists questioned its affinities to Galloanserae and even its classification as a neornithine bird. McLachlan et al. (2017) considered the family Vegaviidae to be stem group birds within Ornithurae. Mayr et al. (2018) claimed that comparison of the plesiomorphic traits of the pterygoid and the mandible does not seem to firmly establish anseriform or galloanserine affinities for Vegaviidae. 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. 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.

Paleobiology
Vegavis was a bird with a high metabolism, which allowed it to live at high latitudes in Antarctica. It also shows a degree of osteosclerosis, a condition shared with Polarornis. This different degrees of osteosclerosis could be related to variations in diving behaviour.