fossil birds and Recent parakeets

[Phillip Bigelow <n8010095@henson.cc.wwu.edu>]

Before I get to my question, a <less than totally serious> solution
to the Dino-pronounciation issue:

   Every time somebody names a new species, genus, or family in a 
   science journal, the editor calls up the Smithsonian Audio-archives
   curators, who promptly pay the author a visit, microphone in hand.
   The author is "encouraged" (read: threatened) to recite the correct
   pronounciation of the taxon 5 times into the recorder.  After
   releasing their grip from the arm of the hapless researcher, the
   archive crew promptly files the quivering voice in a file on CD-
   ROM.  Then, Dino-philes of the 21st Century can savour, with the
   appropriate awe, the voice of their favorite paleontologist.

                ( 5 recitations is necessary, in case the author
                  mispronounces the name the first 4 times).


Now to my question.  A few years ago, the dominant belief amoungst
paleo-ornithologists was that modern birds are monophyletic above the
level of <I think it is> the clan that Hesperornis belongs to.  OK, I can
buy that reasoning.  The major proponents of this phylogeny (I believe
it was Olson, and possibly Feduccia as well), also proposed that the
split between "shore" birds and "land" birds happened in the 
Late Cretaceous.  

My questions are these (they all relate to semantics...sorry folks):

1) My long-held understanding of monophylogeny is that it is defined
   as the radiation of organisms from a "common" ancestor.  But 
   couldn't a "common ancestor" be defined as a genus, or even, in
   some rare cases, a family?  As I recall the definition in it's
   strictest sense, a "common ancestor" is a group of individuals of
   a single species that radiate (through speciation), due to 
   geographic isolation or whatever.  But the problem with modern
   birds is that, because of the constraints placed on their
   skeletal structure to enable them to fly, taxonimists have a
   hard time seeing enough differences in their skeletons to use
   bone structure in their phylogeny.  Flight apparently causes
   hyper-convergence. In fact, so does perching (the developement of the
opposable claw is required for any bird who spends nearly all of it's time
in the trees, regardless of it's ancestory). 

2) Could it therefore be possible that modern birds are actually
   polyphyletic, and we just don't have any way to distiguish between
   primitive and derived traits?

3) If birds are monophyletic from a single species, _before_ the
   KT boundary, then that assumes that either birds suffered a 
   near-extinction sometime in the Cretaceous, _or_ that there was
   only one clan of flying theropod in the first place. 

4) Does Sinornis from the lower Cretaceous have any pleisiomorphies
   that Archeopteryx lacks?

5) If all modern birds are monophyletic above the level of Hesperornis, what is 
the name of this clade?  I can find no name for it in the literature. 
                                <pb>