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Re: Postorbital process of jugal question....



Kris Kripchak (MariusRomanus@aol.com) wrote:

<Just a quick question for anyone who can answer it... For argument's
sake, let's say you were up late last night watching yet another foot of
snow fall from the sky and wondering about the relative placement of the
postorbital process of the jugal in derived dromaeosaurs and
troodontids,... but you couldn't really find anything in the mess you call
your library that spells it out. Could anyone please fill me in on who's
postorbital process was more caudally placed in respects to one another?>

  Troodontids have a typically more slender, elongated jugal, largely due
to the elongation of the orbit to the skull, much greater than in
dromaeosaurids with the exception of forms like *Bambiraptor,* or possibly
*Sinornithosaurus.* The caudal displacement may be nothing more than the
reduction of the bony struts and elongation of the rostral, suborbital
ramus and its apparent "pinching" directly below the eye. This occurs in
*Troodon* at least more than it does *Velociraptor,* *Deinonychus,* and
*Dromaeosaurus* (arguably the most derived form, least bird-like), and
*Sinornithosaurus;* not in more bird-like forms such as *Microraptor* or
*Bambiraptor,* who show longer, shallower, more troodontid-like jugals.
The structure in *Sinovenator* is unknown, and that of *Sinornithoides*
and *Saurornithoides* resemble *Troodon,* so this may be a plesiomorphy
that derived dromaeosaurids reversed to the pre-deinonychosaurian
condition (if they form a monophyly).

=====
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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