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Re: Pterosaur morphological evolution



Michael Habib <MHabib@chatham.edu> wrote:

> Good point.  Again, perhaps it was a biped launcher, instead.   It is also
> possible for a quad launching animal to use a more balanced force output
> from the hindlimbs and forelimbs - it doesn't have to be forelimb dominated,
> but quadrupedal launching should tend to favor a forelimb-dominated cycle
> because it improves multimodal efficiency (i.e. robust forelimbs improve both
> launching and flight for a quad locomotor, so the most mechanically efficient
> mode is robust forelimbs and gracile hindlimbs).  Competing demands could
> lead to robust hindlimbs, or perhaps Raeticodactylus was just largely bipedal.


As you say, robust forelimbs would benefit both flapping flight and
quadrupedal launches.  Hence, pterosaur forelimbs were typically more
robust than the hindlimbs.  The ancestral state for pterosaurs was
likely the opposite of this.  As noted by Mark, _Raeticodactylus_ also
had a very long and slender humeral shaft (although the deltopectoral
crest is well-developed).  The slender humerus and dinosaur-like femur
(insofar as the perp femoral head is concerned) are likely
plesiomorphic characters.  Phylogenetic analyses differ over whether
or not _Raeticodactylus_/_Caviramus_ is among the most basal
pterosaurs or not.  Nevertheless, greater emphasis on bipedal
locomotion is something one might expect in a basal pterosaur.


Superficially at least, the skull of _Raeticodactylus_ is eerily
theropod-like.  One study interpreted it as an omnivore that fed on
small prey and plants.


> Interesting stuff all around!


Most definitely.





Cheers

Tim