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Re: flights of fancy (or "I'm brave, but I'm chicken****")




On Tue, 5 Dec 1995, Mickey Rowe wrote:
>  Since Ostrom first claimed that Deinonychus had
> the semi-lunate carpal bone, people have wondered why Deinonychus
> might have wanted to fold its hands in like a bird.  Maybe it was more
> efficient for the animal to tuck in its arms during a high speed
> chase.  Maybe that's the reason for that adaptation (exaptation?).
        This seems very unlikely, given the fact that it was not evolved 
this way among other dinosaurs or vertebrates. Wouldn't a camptosaur, 
hypsilophodontid, duckbill, bonehead, dryosaur, fabrosaur, ceratosaur, 
allosaur, kangaroo, jerboa, basilisk, or any other animal that spends a 
lot of time on two legs find folding 
arms just as useful? Yet none of these have evolved folding arms. None, 
among all the groups of bipedal predators and herbivores, evolved folding 
arms except for those closely related to the Archaeopterygians. If you 
assume that dromaeosaurs had inherited them from flying ancestors, the 
explanation is easy: the original ancestors evolved folding arms to 
minimize the resistance caused by the wings when walking, either to wind 
or to vegetation, and to protect the feathers. Dromaeosaurs simply
inherited these.        

        -nick L.