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Re: To climb or not to climb



I admit to not having read all of the postings on this topic, so I may be 
repeating what has already been suggested.  I apologize, if that is true 
(I think Ralph Miller hinted at some of these same ideas).  Patrick 
Norton's comment about animals NOT developing bipedalism AFTER taking to 
the trees (with birds being the possible exception) inspired me to 
suggest that dromaeosaurs may have been somewhat unique in this regard 
(remember, my position is that it is OK to have unique animals without 
analogies, living or dead).

The Mongolian Velociraptor fossilized while holding onto a Protoceratops 
in position to be slashing at its underside confirms that dromaeosaurs 
used their relatively long arms and well-clawed fingers for grabbing prey 
and holding onto it.  Perhaps they also developed the ability to grab 
onto a tree and hold onto it.  In other words, they could climb trees 
using all four limbs, like quadrupeds, and in a way that no other 
theropods could.  Thus, they were obligatory cursorial bipeds that were 
facultatively arboreal quadrupeds.  I'll bet there is no term for that 
concept.  

Birds are different--they are bipeds when in trees also, and I would 
guess that is because of the perching foot.  Don't all other quadrupeds 
that climb use all fours?  Is this chronology right?:  the earliest birds 
still had grasping hands (e.g. Archaeopteryx), even after developing a 
foot capable of perching (e.g. Sinornis), but shortly after that the 
carpometacarpus emerged (e.g. Confusiornis) since the hand was no longer 
needed to hold onto branches.

I won't add to the speculation about why dromaeosaurs may have been in 
trees, except to point out that if they lept from trees, perhaps onto 
prey, that might well have favored improvements in aerial acrobatic 
ability.

Bottom line:  the unique killing style of small dromaeosaurs led to 
arboreal ability and ultimatley to avian flight.


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Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu




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Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu