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Re: Oviraptor Palatines



I wrote:

<<The triradiate palatine in _oviraptorids_ is possibly
convergent, as Mickey says [well, okay, he say "probably" :)],
but this does not say much for *Archaeopteryx*>>

Rob Gay (rob_redwing@hotmail.com) wrote:

<So, would secondarily flightless oviraptors eliminate this
"convergence"?>

  The position of oviraptorids and birds is questioned by some
authors, and so I don't feel clean on taking a side. I generally
don't side with any given hypothesis, understand, nearly least
of all this. However, there are several evolutionary scenarios
that I will run through on this:

--+--Tyrannosaurus
  |--Ornithomimosaurs
  |--Troodonts
  `--+--Dromaeosaurs
     `--+--+--Segnosaurs
        |  `--+--Oviraptorids
        |     `--Caenagnathids
        `--Birds

  This tree posits the gut of Elzanowski's position, that of
oviraptorosaur/bird monophyly exclusive of dromaeosaur
interference. The position of the other taxa is irrelevant, for
now, because they do not concern the major avian node. This is:
the triradiate occurs once in avian evolution, as the
oviraptor+bird synapomorphy, and is reversed in caenagnathids.
Caenagnathids may represent the plesiomorphy, whereas birds,
segnosaurs, and oviraptorids acquire this each separately. The
second is one step longer than the first (more parsimonious) as
long as only the palatine and ectopterygoid are considered.

--+--Tyrannosaurus
  |--Ornithomimosaurs
  |--Troodonts
  |--+--Segnosaurs
  |  `--+--Oviraptorids
  |     `--Caenagnathids
  `--+--Dromaeosaurs
     `--Birds

  Dromaeosaurs are also considered closer to birds, so that the
palatine and ectopterygoid are acquired separately in birds and
oviraptorids. The same is true even if troodontids are closer to
birds than dromaeosaurids:

--+--Tyrannosaurus
  |--Ornithomimosaurs
  |--+--Segnosaurs
  |  `--+--Oviraptorids
  |     `--Caenagnathids
  `--+--Dromaeosaurs
     `--+--Troodonts
        `--Birds

  And that's as much as I would be brave enough to say ... for
now :).


=====
Jaime A. Headden

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

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