All of southamerica (with one or two exceptions) and oceania animals should be there in base game.
Gonna have to second this. With both of these regions having pretty much the bare minimum right now I really don't want to have to wait to get even that again. Oceania's current roster is a solid one
to start off with, but I don't think it's one the game should
end having, and South America is just a trainwreck lol. I don't think you'd really have to pull these guys back to sell DLCs either once you start introducing flyers and aquatics, since both of these regions are jam-packed with iconic essentials that could easily sell, from the obvious macaws to lorikeets, cockatoos, harpy eagles, condors, birds of paradise, sirenians, South Pacific and Amazon river fish, hell maybe even vampire bats depending on how the system for animals that small works out.
Same goes for some taxonomic groups like birds and primates (with some exceptions for the latter). A good starting point, but I don't want to have to wait to get to it again.