To climb or not to climb

["Norton, Patrick" <Patrick.Norton@state.me.us>]

<I think there may have existed a reason for Dromaeosaurs to climb that   
had
nothing to do with feeding, or direct predator avoidance. >

The difficulty I have with respect to tree climbing dromaeosaurs is, what   
seems to me at least, an inherent conflict in selection pressures. I view   
obligatory bipedalism as one response to pressures in animals with a   
primarily cursorial lifestyle, while quadrapedalism (or some form of   
quasi-bipedalism) usually seems to be selected for animals with a   
primarily arboreal lifestyle. Within that framework, it's difficult for   
me to see an evolutionary scenario that would result in obligatory bipeds   
such as dromaeosaurs inhabiting an arboreal niche.

A notable exception to this may appear to be the birds.  But birds would   
have avoided this evolutionary paradox if it turns out (which seems to be   
the case) that they did not evolve arboreal characters (perching feet,   
etc.) until after the evolution of flight.

My two cents. Open fire!

Patrick Norton
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