Re: To climb or not to climb

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

Dinogeorge said:

<I think you have this exactly backward. Most large mammals are   
non-arboreal
quadrupeds. >

You misunderstood me. You are, of course, correct that most large mammals   
are non-arboreal quadrupeds. What I said, however, was that selection   
appears to favor quadrapedal or quasi-bipedal locomotion in arboreal   
animals. Evolution has certainly shown that quadrapedism and bipedalism   
are both viable locomotive options for cursors.  My basic point is that I   
can't think of one example of an animal that has evolved an obligatory   
bipedal stance while occupying an arboreal niche (hominids came down from   
the trees before they walked fully upright.) There are no obligatory   
bipeds in the trees, except birds.  And if birds evolved obligatory   
bipedalism in an arboreal niche, they would appear to be unique example.   
 I would go further and suggest that, as obligatory bipeds, dromeosaurs   
would seem to be an ecological exception if they spent much (or any) time   
in trees.

Patrick Norton