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Re: Deinonychus Morphological Variations within Ontogeny



Gregory S. Paul  <GSP1954@aol.com> wrote:

> Essentially all deinonychosaurs including Archaeopteryx have a strongly
> laterally facing shoulder glenoid that allows a flapping motion of the arms.
> Some of this information has been in the literature well back in time, I saw
> it examining the Archareopteryx and Deinonychus specimens in the 80s. As I
> diagramed in PDW, it is also true of some basal theropods, such as
> Coelophysis. So there is no reason to doubt that dinobirds could flap their 
> airfoils.
> Their glenoids did not face as dorsally as in more derived birds, so they
> probably could not elevate their wings fully vertically. That would have very
> probably limited aerial climbing performance -- including an inability to
> achieve vortex inducing wing clapping that pigeons for example use to help
> rapidly climb nearly vertically from a ground take off.


I agree that even rudimentary flapping could generate thrust, so some
powered flight is possible in _Archaeopteryx_ and friends (such as to
control or extend a glide; or maybe even for brief flutters off the
ground to clear a fallen trunk or narrow waterway).  But I doubt that
*sustained* powered flight was possible.  The pectoral musculature and
feather (remiges) structure argues against the ability of the wings to
be able to gain or maintain height once airborne.



For some reason Greg's email landed in my junk folder (yet assorted
emails about bogus conferences got through... thanks Gmail).  My
apologies for the late response.






Cheers
Tim