Re: L'origine et l'évolution des oiseaux, with a

[Tim Williams <tijawi@yahoo.com>]

David Marjanovic wrote:


> I'm aware that "cursorial" doesn't mean
> "_can_ run" but rather "regularly does it for
> a living"; but that's what the leg proportions of
> *Sharovipteryx* suggest, if we kindly ignore the short toes
> and the patagium which imply another possibility.


Yes, exactly.  If _Sharovipteryx_ was preserved without a patagium it would be 
reasonable to assume that it was a biped, given the disparity between the 
lengths of the forelimbs and hindlimbs.  But because a patagium was preserved 
attached to the hindlimbs, it puts a wholly different complexion on the ecology 
of _Sharovipteryx_.  The hindlimb supported a membrane.  Gliding and flying 
vertebrates typically elongate the forearm bones to increase the overall length 
of the forelimb that supports the wing or patagium.  In _Sharovipteryx_, it's 
the hindlimb that supports the wing/patagium, so it makes sense for the tibia 
to be elongated.


Cheers

Tim