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Re: pteros have lift-off
David Peters wrote:
> Greg Paul in dinos of the air suggested that Archaeopteryx and other
> birdy descendants of short-armed theropods gained their long arms from
> tree-clinging and tree-climbing. Is this the general consensus?
I don't believe so. (Are you sure Greg Paul actually said that??
Specifically, did he actually say that _Archaeopteryx_ evolved from
Elongation of the forelimbs is a character that appears to be primitive for
coelurosaurs. Those coelurosaurs with relatively short forelimbs (e.g.,
compsognathids, alvarezsaurs, _Caudipteryx_, _Austroraptor_) appear to
represent secondary reversals of this character. Forelimb elongation could be
associated with the need to grasp branches, and/or a shift to aerial
locomotion; or it could be associated with improved reach in prey capture.
> Padian championed bipedal locomotion. Bennett followed von
> Huene who championed arboreal leaping and illustrated
> Eudimorphodon's hind limb in a leap. No one else I am
> aware of has broached the subject. If you choose dinos or
> Scleromochlus as sister taxa, you have long hindlimbs and
> short forelimbs. The same if you choose Cosesaurus and
> Sharovipteryx. No other taxa have been promoted seriously
> with matrices.
The thing is, while the above paragraph is technically correct, it omits one
crucial detail: pterosaurs have long forelimbs and short hindlimbs. We do not
know what the intermembral indices were for those (as-yet-unknown) pterosaur
ancestors that exhibited incipient flight behaviors.
Further, AFAIK, no obligately bipedal prolacertiforms or basal ornithodirans
are known, and the Prolacertiformes and basal Dinosauromorpha plexus both
include non-bipedal forms. So I don't think we can assume that the first
aerial pterosaurs (or pterosauromorphs) were bipedal.