Re: pterosaur femora sprawl

[Michael Habib <mhabib5@jhmi.edu>]

> Here's the alternate that makes more sense: As published in Peters 
> 2000, 2002, 2007, I favor a bipedal pre-volant stage at which time the 
> hands. freed from locomotion, could have been locked into the 
> pterosaur configuration of producing laterally-oriented prints while 
> maintaining a 30 degrees-out orientation of the elbow.

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.

> On the other hand, if continuously quadrupedal, then there had to have 
> been a series of taxa with an increasingly laterally-oriented manus 
> (what would have caused this??). And why would that have occurred on 
> the road to dinosaurs or dinosauromorphs since they were experimenting 
> with bipedalism, little fingers and digitigrady (Scleromochlus comes 
> to mind)?

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.

>  And what's the new scenario?

Good question.  I'll counter with another question, though - must we 
have a scenario to infer character polarity?

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