The oldest member of what is, unfortunately, officially* called Aves is not the late Maastrichtian
Vegavis and not the end-Maastrichtian
Asteriornis. Most likely it is the presbyornithid stem-anserimorph
Teviornis, which is from somewhere low in the Nemegt Formation. That seems to mean it's from the very beginning of the Maastrichtian or older. (For the meaning of "seems", watch
this space.) If you read the so-called supplementary information** of the
Asteriornis paper, you'll find the authors were aware of
Teviornis and didn't even try to argue that it wasn't a member of Aves.
The latest phylogenetic analyses have found Vegaviidae outside Aves. But if it's inside after all, keep in mind that the oldest known vegaviid is probably not
Vegavis (or
Polarornis or
Neogaeornis, all late Maastrichtian) but
Maaqwi, which is end-Campanian (so about the same age as
Teviornis).
*In Phylonyms, the starting point of regulated phylogenetic nomenclature; its registration number is 113. Go
here, click on the search result, then click on "Definition".
**
Always read the supplementary information. That's
particularly important in Nature, Science and PNAS, where the "paper" is just an
extended abstract and the "supplementary information" is
the actual paper.
Asteriornis deservedly came out in Nature.
Gesendet: Dienstag, 27. April 2021 um 21:41 Uhr
Von: "Meig Dickson" <mdickso2@uic.edu>
Alternatively, we go the *fun* route and say all members of Pan-Aves are Birds (since they're more bird than anything else), and then, well, there was some sort of avemeta-thing in Poland in the Early Triassic...
Not that I know of. Are you thinking of the stem-archosauromorph Osmolskina?