Re: Fastovsky vs Archibald

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<Perhaps not convergence, but in any way the "velociraptorine" type seems to be
the plesiomorphy -- *Sinornithosaurus* has it.>

  Actually, the reason I noted convergence had nothing to do with a
differential distribution exclusive of other dinosaurs, but because a crown
with larger posterior denticles than anterior and denticles that hook towards
the tip involve two discrete characters with a more variable expression in the
fossil record. That they are shared within dromaeosaurids so neatly with a loss
of expression in *Dromaeosaurus* argues the selection for this as an advantage
in their mode of feeding. Larger animals vary in the expression: *Utahraptor*
has "dromaeosaurine" dentition, indicating lack of a selection for posterior
"slicing" but rather for piercing, as would appear to be consistent with
*Dromaeosaurus* and of course the tyrannosaurs and *Richardoestesia*. Hooked
denticles are present throughout Maniraptora.

  Teeth are extremely plastic structures.

  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)

"Human beings, who are almost unique in having the ability to learn from the 
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