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



GO writes:

> 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?).
>
>No, the reason is more likely to be that _Deinonychus_ had a volant ancestor
>somewhere in its family tree. Why is this so difficult to accept?

Why should your explanation be the better of the two in this case?  Do you
have any evidence that the arm-tucking explanation (which makes sense to me)
is not valid?

Of course the two explanations are not mutually exclusive - but if the
functional adaptation is reasonable how would you establish (short of
linking forms or analysis (cladistic or otherwise) of other characters
showing that D. was closer to some winged forms than those winged forms were
to others) that the other explanation also applied?  Saying that it makes
more sense may be good debating style, but it isn't evidence.

>As I said above, I never claimed that humans were perfect models for running
>theropods. The point I was trying to make is that a running animal that
>evolves feathers on its forearms would be in the position of a human runner
>trying to run while wearing a long-sleeved coat--that feathers in those
>locations would tend to hamper rather than help. 

Except that it might well have developed adaptations to counter this
problem.  After all, an Ostrich is an extremely fast runner with
fairly-large, well-feathered wings and it seems to manage.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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