Re: pterosaur femora sprawl

[David Peters <davidpeters@att.net>]

 MHabibwrote:

> Why do the forelimbs need to be "freed from locomotion" to undergo 
> adaptive change?  I'm unclear as to why this alternative makes more or 
> less sense than a quad ancestry.

If we look at birds and bats, the other volant tetrapods, both got their wings 
after a bipedal phase (bats inverted). Peters 2000 showed, via 
Langobardisaurus/Cosesaurus/Rotodactylus and Sharovipteryx that a bipedal phase 
was also a part of the pterosaur story. There are no published alternate 
scenarios for the rotation of the planted hand. And still no alternate genera 
proposed that test closer to pterosaur origins.


> We don't know what the selective situation was, at present.  But that 
> does not restrict us from detecting the trend.  There are plenty of odd 
> anatomical features of pterosaurs for which the selection regime is not 
> known; but we can still make phylogenetic inferences about them.

We certainly can. Where else do you find more pterosaur synapomorphies than in 
the obligate biped Sharovipteryx? That's the challenge to the once a quadruped, 
always a quadruped proponents. Any takers?
> 
> 
> Good question.  I'll counter with another question, though - must we 
> have a scenario to infer character polarity?

I don't know. But that's what the list is all about. 
> 
> Cheers,
> 
> --Mike H.
> 
> 
> Michael Habib, M.S.
> PhD. Candidate
> Center for Functional Anatomy and Evolution
> Johns Hopkins School of Medicine
> 1830 E. Monument Street
> Baltimore, MD 21205
> (443) 280 0181
> habib@jhmi.edu