Flyers and atmosphere

Dryornis by HodariNundu. Its been argued the disappearence of giant flying birds like it is related to the thinning of the atmosphere in the Pleistocene.

A recent study proposes that giant Cenozoic flying birds like pelagornithids, Argentavis, Dryornis and giant storks went extinct due to the thinning of our atmosphere in the late Pliocene/Pleistocene, disallowing them from powered flight.

This is not the first time atmosphere density has been proposed to have affected flying animals. A slightly earlier study suggests that the denser atmosphere of the Eocene allowed bats to develop powered flight, and the denser atmospheres of the Mesozoic have continuously been cited for larger sizes in pterosaurs (a notion paleontologist Mark Witton has continuously disagreed with).

I’m rather conflicted on this. On the one hand, it does seem convenient most large flying birds over 3 meter wingspans disappeared in the Pliocene/Pleistocene transition. On the other hand, the study ignores a recent study on Leptoptilos robustus, which showcases it was still a capable flyer despiste living in the mi/late Pleistocene.

I wonder if the pterosaurian quadrupedal launch would have negated the effects of atmospheric thinning. Certainly, flying machines orders of magnitude larger than any flying mammal still operate, some with relatively small wings.

Food for thought.