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Re: Island-dwelling dinosaurs (was Re: Gargantuavis neck vertebra)
Do we really know this?
Of course not. :-)
Especially for the ratites: how good is our timing of the origin of
flightlessness in this bunch?
The oldest rhea, *Diogenornis*, is Paleocene. Because it's recognizable
as a rhea, I suppose it's known to be flightless.
The ostriches may be related to some (particularly *Palaeotis*) or all
of the European Eocene and Paleocene (like *Eleutherornis*) supposed
The other ratites aren't known from that far back, but neither are
possible volant ancestors... except, as was presented at the conference
this week, there's now a kiwi from the Miocene of New Zealand that was
so small and so incompletely known that it might have been able to fly
(according to the presenter, Trevor Worthy).
The other large flightless birds (gastornithids, brontornithids,
dromornithids) reach down into the Eo- or Paleocene as well, and
likewise lack a fossil record before that.
Finally, this isn't my idea; IIRC, it comes from one of the big 2008
papers on neornithean phylogeny that found ratite paraphyly.
Furthermore, crocodylomorph and squamate terrestrial predators were
present on both Laurasia and Gondwana at this time.
Not clear how far down they reach, except for *Titanoboa* which wasn't
Additionally, phorusrhacids seem to have developed flightlessness in
the presence of marsupial terrestrial carnivores.
Perhaps not. The oldest known phorusrhacoids are as old as