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RE: a little background



 
Mike Taylor wrote:

>John,
>
>Please NEVER apologise for long and interesting posts on this list!
>It's been excellent on here in the last few days: controversial paper,
>lots of discussion, and -- best of all -- the author on hand to
>explain where we're all missing the point!  Many thanks for taking the
>time.

I'll second that!  A heartfelt thanks to those professional paleontologists
who stick around on the DML, and put up with the likes of me.  I don't know
how you do it sometimes; but I'm sure glad you do.


>Then it occurred to me that a while back when I saw film of an ostrich
>running, it seemed to be doing something very similar to that: at
>least, it _appeared_ (though all those fluffy feathers might by hiding
>the truth) that its centre of mass was _well_ forward of its feet as
>it ran.  So that seems an extra reason to be interested in how well
>ostriches fit your body-mass/leg-muscle-mass graph.

Ostriches are birds - and neornithine birds at that.  In in birds more
derived than _Archaeopteryx_, a rearrangement of the postcranial skeleton
(plus the big head!) shifted the centre of mass forward of the hips.
Secondarily flightless birds have rectified this to some extent by the
re-orientation of the femur.  As Greg Paul mentioned, the femur continues to
participate in hindlimb locomotion, but not to the degree inferred for
non-avian theropods.  


Tim


------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163