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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 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?


--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