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

[David Peters <davidpeters@att.net>]

> 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<<

Point 1. There's evidence for uropatagia in Cosesaurus (femur=tibia) so the 
'makes sense' comment is falsified. Also extra membranes/flesh in Macrocnemus 
and Tanystropheus.

Point 2. Sharovipteryx was not always gliding. Sometimes it was sneaking up on 
something. Othertimes it was positioning itself for a drink of water. And you 
can think of dozens of other scenarios in which flight was not involved. 


David Peters
davidpeters@att.net