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Re: BEAKS etc IN THEROPODS



Darren Naish (darren.naish@port.ac.uk) wrote:

<Tim already pretty much answered this, but same answer: Maniraptoriformes
is a more inclusive group than Maniraptora, so if all maniraptorans are
beaked, that doesn't mean that all maniraptoriforms are. I don't think
tyrannosauroids were beaked, nor non-maniraptoriform theropods like
abelisauroids or allosauroids. Among non-maniraptoran maniraptoriforms we
know of course that ornithomimosaurs were beaked.>

  Then what are the criteria? Except for part of the snout in some
*Gallimimus*, the snout of most ornithomimosaurs are smooth, however
foraminated. But if the snout of carcharodontosaurs and dromaeosaurines,
similarly rugose and arranged in dorso-oral arranged vascular channels
with extensive foramina, why cannot this condition be a cornified skin
leading to a "beaky" structure on the smoother portions of the skull? And
why is the face of *Carnotaurus* not completely covered in the horny
material, versus *Triceratops*, whose smooth, vascularized and weakly
foraminated face and dorsal skull (including the frill) have also been
linked to a cornified skin? As in birds, there is a great deal of
underlying variation occuring with regards to birds. Lets regard the whole
Archosauria as bearing a "cephalo-theca" and be done with it. Either, or
find actual universal criteria that apply to fossils that will permit us
to determine beyond a doubt that there was a rhamphotheca, cornified skin,
etc., or not.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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