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Re: A question about Feduccia's claim of convergence



Lonnie (Anakinsdream30@aol.com) wrote:

<Feduccia says: "Convergence is an insidious and treacherous
trap, baited and waiting for the unsuspecting worker and Nowhere
has the trap been more successful than in luring paleontologists
to the theropod dinosaurian origin of birds".>

Ken Kinman (kinman@hotmail.com) wrote:

<<I have also sometimes chided cladists for allowing themselves
to be fooled by convergences and other homoplasies. However in
this case, it seems rather improbable that theropods and birds
could have developed such a large number of convergences.>>

  Funny how no one has yet suggested that Feduccia himself has
fallen prey to the convergence-scenario.... His shorebird
hypothesis seems not to have gained too much favor, and using
what he feels to be "strong" characters (Feduccia, 1996), he
then uses simple broad forms of whole portions of anatomy to
unite birds and various thecodont groups [anything but a small
running dinosaur, that is].

  One part of cladistics is to weed out convergence by using
parsimony, bootstrapping, and simple relative comparison of
different trees. You may note that occassionally the most
parsimonious tree is not always favored by the authors, due to
likelihood evaluation of what else that tree produces (see Zhang
et al, 1999, on *Chaoyangsaurus*). And possibly, the knowledge
that while, so Holmsian the phrase is in scientific usage,
parsimony does not neccessarily mean its right. Just of "the
likliest that we produced" mein. Strong support for groups (30
or so characters for Ceratopsidae, much less for Diplodocidae)
can be considered realistic when likelihood trees suggest
polyphyly or otherwise. It's all relative.

  I would not stake my reputation on a cladistic analysis --
ever; but not also on a simple morphological or molecular
analysis, either. A synthesis, perhaps, but not each individually.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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