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Re: pterosaur femora sprawl
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
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?
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181