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Climbing and Cynocephalus

Thanks to Matt Troutman for his last couple posts on climbing. I'm   
interested in hearing more about his thoughts.

In his post on CLIMBING, Matt said:

<<I stand by Witmer's (1997) conclusion that pnematization by use of air   
sacs is something that can be exapted for many things.  Yes, they may   
have been
exapted to make a lighter weight, but this in itself does not directly
support the climbing hypothesis because the easiest way to reduce weight
is to evolve a small size.>>

I recently had a discussion about this with someone who made me realize   
that getting lighter is one possible benefit of pnuematic bones, but   
getting bigger without getting heavier is another.  All else being equal,   
a 100 Kg animal with pnuematic bones would be larger than a 100 Kg animal   
without pnuematic bones. If the mass lost by pnematization were   
applied--for example--towards slightly longer legs, you could have a   
faster animal as well.

And in his follow-up post on CYNOCEPHALUS, he said:

<<Yalden (1985) considered_Cynocephalus_ to be the closest living analog   
to _Archaeopteryx for several reasons.>>

Yalden considered it a moderately close analogy, but as Matt indicated he   
didn't push the analogy beyond trunk climbing; for good reasons in my   
opinion.  Even though the flying lemur is completely arboreal, it is   
actually very awkward in the trees. Its large patagium and non-opposable   
thumbs make movement among the branches very difficult. In fact, they   
often get around in trees by hanging upside down by their claws like the   
South American sloths. Archie was probably more agile among the branches   
and was certainly equipped to pursue cursorial activities as well.