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Re: New Cretaceous bird and other papers




On Sun, 17 Feb 2002, David Marjanovic wrote:

> ...there were enants everywhere in the world except in Antarctica in the
> Maastrichtian. Evidence: All known birds from the Maastrichtian site on
> Seymour Island (next to the Antarctic Peninsula) are Neornithes.

Underlying discussions of this sort may lurk hefty biases.  Mine is that
extinction is a complex ecological phenomenon.  Statements such as yours
above are music to my ears.  You are saying (I think) that neornithines
outcompeted enantiornithines in the Antarctic and (presumably) other parts
of Gondwana.  The "event", then, just greased the wheels for neos,
facilitating their inevitable global domination a little earlier. 

> ...the effects of an impact depend on latitudinal distance. Then Antarctica
> is as far as you can get.

The fate/role/ of birds in these extinctions is at present a wildcard.  We
have little evidence to go on.  So, there is room to entertain
hypotheses such as this: the prior extinction of most pterosaurs was due
to bird competition (they _must_ be the prime suspect); if neos
outcompeted enantis in the south, they _may_ have also done this in the
north.  Superior competitiveness against enantis may well translate to the
same against pterosaurs (e.g., now, the image of a falcon snatching
pterosaur babies, is not outrageous).  In short, modern birds affected the
distribution of species _before_ the event.  In this view, the
seminal event was not the bolide, it was the appearance of neornithes.

> ...100 % of non-neornithines died out, along with (guesses) 99 % of
> neornithine species and 99.999 % of neornithine individuals.

As you say, these are guesses. There is no evidence to inform them.

> ...100 % of Neornithes died out everywhere north of (guess) 20 south.
> Allows for survival of ratites in New Zealand, Madagascar and India as
> predicted (but maybe not necessary, assuming that the ratites of that time
> were not flightless) by the newest mtDNA phylogeny of ratites.

You accept _this_ molecular evidence, then?