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Re: Viva Neornithine Birds!

David M. said:
If one breeding pair -- or even just a female capable of parthenogenesis,
in the case of Neornithes at least -- survives a mass extinction, all clades
it belongs to have survived.

How is this relevant when what we are talking about is origin of _different_
clades before the boundary?

If ten clades survived, that means ten breeding pairs must have survived. Twenty birds in the whole world is still not what I'd call "mass survival" or use to argue against the size of the impact. 100 or 1000 worldwide would still not be "mass survival".

This is different from the hypothesis that the
mass extinction didn't affect those clades at all, and yet again different
from the hypothesis that the mass extinction consisted of said clades
outcompeting others. Remember: you need to find all possibilities because
you can't test hypotheses that you've never thought of. 

And yet many were content with the "shorebird" hypothesis and somewhat
insistent on its exclusivity

Well, it was wrong. This latter fact, however, still doesn't tell us much about the diversity of Neoaves during the K.

There are two primary sets of hypotheses.  One set is inspired by a glib
attraction to _luck_.

That is a misrepresentation. Given that huge crater, what do we expect, and do we find those expectations confirmed? So far we find many of them confirmed, and haven't managed yet to disprove any.

The other involves the attributes of different
species.  New data cull hypotheses.   The more clades of neornithine birds
whose divergence dates before the boundary, the less random are the
extinctions, i.e., we have to look for reasons: why neornithine and not
enantiornithine survival.

Quite so. You just can't cite Livezey & Zusi either way, because they don't say anything new.

Do the data lead us to look harder at the southern continents? 

It certainly wouldn't hurt.

If so, are we talking about a pre-boundary dominance
of neornithines there;

That remains to be answered, but what we currently have -- the Maastrichtian of Argentina, with a wide ecological diversity: *Enantiornis*, *Neuquenornis*, *Lectavis*, *Yungavolucris*, *Soroavisaurus* -- argues against that idea, even though it doesn't disprove it.

followed by significant survival

That is yet another question. Molecular dating argues against the idea that *Polarornis* and *Neogaeornis* were loons -- so do we have a clade of neornithines here that went extinct at the K-Pg boundary? We still don't know.

due to less intensive bolide effects [...]?

Why do you speculate about the causes of a phenomenon you haven't even observed yet? :-)

I was not trying to mislead...my intent was to use the authority of Livezey and
Zusi to weigh in heavily on the molecular data--

Oh! Sorry! I'm just not used anymore to pure unadultered arguments from authority, so I had to assume you were trying to say Livezey & Zusi's _data_ supported your conclusions. I recommend you don't repeat that: firstly, arguments from authority are unscientific; secondly, Livezey & Zusi are not even authorities on molecular phylogenetics or divergence dating in the first place.