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Re: Brochu's avian article in latest JVP




>Dr Holtz has just reminded me of a question I had about Chris Brochu's
>recent JVP article on the current theories of non-dinosaurian origins of
>birds.
>
>In the article Dr Brochu refers to 4 published phylogenies of the
>earliest avian and possible avian taxa.  Hoever the article >seems< to
>be addressing Feduccia and Martin's claims to a crocodylian origin for
>Aves, and yet none of the phylogenies discussed were that of Mssrs
>Feduccia and Martin.
>
>I know there's a great deal of cladistics I don't understand but this
>seemed rather odd to me.  Is it that Feduccia and Martin have not
>suggested a phylogeny, so that it can't be discussed?   How can you use
>existing phylogenies to argue for or against a phylogeny that is
>unreferred to?  WHY would you?
>
>Had I gotten the gist of the article wrong?
>



Somewhat wrong.

Actually, Mark Norell and I were addressing several putative non-dinosaur
alternatives to bird origins - crocodyliforms, crocodylomorphs, various
"thecodont" hypotheses (although the term "thecodont" is phylogenetically
meaningless), Megalancosaurus, and so on.  These were referenced in the
paper.

We also state that people like Feduccia and Martin rarely, if ever, present
an explicit set of relationships.  We couldn't include specific phylogenies
from them because there aren't any, with rare exceptions (e.g. the trees in
Whetstone and Wybrow or in Hecht and Tarsitano).  This is a problem, but
one the other side of the "debate" (such as it is) has to resolve - if you
think placing birds somewhere other than Dinosauria improves stratigraphic
congruence, let's see the tree; don't just tell us that birds are related
to some sort of thecodont or crocodylomorph.  We simulated their ideas by
pruning birds from Dinosauria and drawing them closer to one of the other
postulated bird relatives.  I'm sure Martin and others will object to these
trees, but if they don't give us an alternative, we have no choice.




chris





----------------------
Christopher A. Brochu
Department of Geology
Field Museum of Natural History
1400 S. Lake Shore Drive
Chicago, IL 60605

voice: 312-665-7633
fax: 312-665-7641
electronic:  cbrochu@fmppr.fmnh.org