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Re: MORRISON TROODONTS






>From: darren.naish@port.ac.uk
>To: dinosaur@usc.edu
>Subject: MORRISON TROODONTS


>I am pretty confident that the fighting  _Velociraptor_ specimen has 
>uncinate processes preserved _in situ_. Anyone with reference to a 
>good photo of the specimen can verify this (I do not have such a 
>photo to hand right now). 

     Try Louie Psihoyas'  _ Hunting Dinosaurs_. Strangely its the only 
picture I can find of the "fighting" Velociraptor and it appears to have 
uncinate-like processes.


>John and I discussed uncinates the other day and (perhaps) unlike 
>him, I do not regard them as phylogenetically informative, mainly 
>because their distribution among taxa is so strange. While 
>_Velociraptor_ has them, _Archaeopteryx_ does not (and I do think 
>that _Archaeopteryx_ is closer to other birds than are 
>dromaeosaurids). Greg Paul thinks that a process figured in Ostrom 
>(1979) is an uncinate from _Deinonychus_, but this is difficult to 
>prove. At last some enantiornithines have them. 

     Uncinates may not be that phylogenetically imformative because they 
are variable in shape, number, and appear to be seperate ossifications 
in dromaeosaurs and possibly ( don't flame me for this anyone please) 
oviraptors ( look at the ribcage of the nesting dinosaur and Ingenia; 
there are strange processes extending from around the ribs which may, 
may be uncinates. 
  
     Enantiornithines lack uncinates. No enantiornithine has been found 
with them. Of course you can enlighten me if you have info otherwise.



They appear primitive 
>for ornithurines (they are very evident in _Hesperornis_),
>snip<

     Liangingornis and Chaoyangia have them too.

 but appear 
>to have been lost several times among neognathans (emus and screamers 
>lack them). And before some of you start to speculate, there is no 
>correlation between flightlessness and/or aquatic/amphibious habits 
>with loss of uncinates, as numerous groups of flightless and/or 
>aquatic/amphibious birds have them.
>
>Before I consult Baumel et al.... time to ask the ornithologists - do 
>the rib's uncinate processes have a known function?

     One obvious one: they bind and stiffen the ribcage together to 
resist forces exerted be the powerful dorsal elevators in flight. 
Basically, to prevent the ribcage from being torn apart. Plus an other 
possible function: ventilate the airsacs ( Ruben, Feduccia.)


>"Now nothing can stop us in the raptorisation of Earth!"
>
>DARREN NAISH
>darren.naish@port.ac.uk
>
>
  
 WMattTroutman

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