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BCF in perspective (long)



        Just wondering...I haven't been paying as much attention to this
whole BCF-BADD issue as I'd like to have been (hey, crunch time is on with
exams and such), but how is the fossil record and predominately accepted
(i.e. BADD) phylogeny reconciled with the BCF concept that birds arose in
the Triassic, and then gave rise to either all dinosaurs (which would then
be birds, not dinosaurs) or all theropods or all coelurosaurians or
whatever?

        In other words, the ultimate question is, what is the phylogeny
proposed by BCF (really briefly)? Did basal theropods arise from birds and
then diversify into coelurosaurs, ceratosaurs, et al? If that, then birds
would be dinosaurs still, unless BCF proposes a paraphyletic "dinosauria"
(saurischia + ornithischia + aves??). Are (according to BCF) birds basal
dinosauria; are they also the ancestors of ornithischia and sauropoda? Does
BCF propose a renaming of Dinosauria?

        Further questions follow: how is the fossil record reconciled with
this new phylogeny (which has been well documented with cladistic analyses
rather than eyeballed for gross similarities, right?)? Taking a
Longisquama-like ancestor for Aves leaves a lot to be explained; where are
the transitional forms between those two? How are the trends within
non-avian (or post-avian) theropod evolution accounted for (in short, did
birds begat dromaeosaurs, which begat non-avian maniraptorans, which begat
coelurosaurs, which begat carnosaurs, which begat ceratosaurs; or what?)?
Does BCF propose that theropod phylogeny is actually the mirror image of
BADD phylogeny, or is there massive polytomy at the bird-nonavian theropod
transition in which all theropod groups arise in the Triassic/Jurassic? Or
what?
        The big picture conjured by BCF just doesn't make sense to me, even
without any speculative stories to explain the origin of flight, which
(sans fossil evidence) are just stories, and inconsequential to the
phylogeny (which must come first). Don't get me wrong - I applaud G.O.'s
effort and obvious hard thought involved in the BCF idea (*if nothing else,
it's been a great mental exercise for all of us*), but a complete phylogeny
is the foundation of the whole hypothesis. Invoking origin of flight
scenarios (which inevitably must depend on the phylogeny proposed) to
explain BCF seems like a circular argument to me. In summation, nice job
G.O., but how about showing us a simple, inclusive version of your
phylogeny? If you're going to convince anyone, that's the #1 thing you'll
need; a phylogeny backed up with solid fossil evidence - not origin
stories. BADD has a reasonably decent phylogeny, reasonably decent fossils,
and (depending on the storyteller of course) a story that's as entertaining
as any other; how about BCF?
        All of this is IMHO of course; I probably made some mistakes (I'm
not yet a mega-cladist, give me time), but I just wanted to get a clearer
view of the issue. Sorry for the War and Peace discursiveness; too much
coffee. :-)

                        John R. Hutchinson
                  Evolving Evolutionary Biologist
                 Department of Integrative Biology
                  3060 Valley Life Sciences Bldg
                University of California - Berkeley
                        Berkeley, CA 94720
                          (510) 643-2109
         http://ucmp1.berkeley.edu/people/jrh/homepage.html