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Re: Coelurosaur Analysis update, with Graciliraptor, Atrociraptor, Sinusonasus,



Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:

<<<`--+--+--Erlikosaurus
      |  `--Avimimus>>>

David Marjanovic replied:

<<An artifact because their skulls are known? :-]>>

<I think so.  Almost all the characters diagnosing it are cranial (long
external naris; toothless premaxilla; anteriorly toothless dentary;
etc.).>

  The length of the external nares is unknown in the referred skull of
*Avimimus*; the fenestra present has a well-defined anterior border with a
distinct rostral rim, unlike most other dinosaurs (not counting
hadrosaurs) for the external naris, but similar to the antorbital
fenestra, especially as in other theropods. Because this is incomplete,
and length of the skull is unknown, actual size of the fenestra and
relative size of it to the skull are both unknown. Margin between maxilla
and premaxilla may be fused, or indistinct, though some (myself) have
inferred that there is a division here at some point between the maxilla
and premaxilla, though I no longer hold this view. Identity as an entire
premaxilla and not any part of the maxilla is similarly unknown. One nasal
is know and appears to be incomplete, extremely short, and preserves what
may be the caudal external narial margin, however this only supports the
oviraptorid condition which have rotated the naris dorsally and retracted
it caudally past the rostral margin of the antorbital fossa. Assuming the
two margins refer to the same fenestra is a stretch of the imagination
even the retracted nares of sauropods do not conform to. The rostral
fragment, in any sense, is completely unique and any assumption of the
nares or antorbital fossa length or proportions thereof should await more
material.

  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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