Re: Dromornithids and size limits.

["Jaime A. Headden" <qilongia@yahoo.com>]

Chip Howell (Vorompatra@aol.com) wrote:

<As I understand it, his argument is that birds have gone too far down an
evolutionary path, with forelimbs that are probably too specialized to
"devolve" into potentially-manipulative appendages (in the case of the
Moa, the wing had disappeared completely, bone and all). Perhaps the same
can be said of some mammals (e.g., cetaceans, sirenians), but I suspect
even bats retain enough of the forelimb structure that they could, given
the right conditions, evolve hands out of their wings.>

  Except that, if one looks at the evidence appropriately, *Titanis* has
been considered to bear a more effective semi-manipulable wrist. This is
assessed based on condylar joints between some phalanges and the
carpometacarpus. Plus, the hoatzin has shown that a large, manipulable
wrist can be redeveloped or retained in juvenility. One would then argue
that birds are not "too far down" indeed.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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