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Re: Let's find the basal Ornithodire.



Dave Peters (davidrpeters@earthlink.net) wrote:

<To do so, all we have to do is come up with something close to the basal
Ornithodire. Some taxon that might be close to the one that gave rise to
Dinosauria, Pterosauria _and_ Scleromochlus. We can even imagine one that
hasn't been discovered yet. What would it look like?>

  We wouldn't need to include *Scleromochlus,* as Dave himself implies
this is a crurotarsan "pre-croc."

  However, the more critical issue, and which has eluded paleontology --
and even Dave's techniques and researches -- has been a "pro-pterosaur"
that shows a long arm with modifications towards flight, as in broadening
of the sternum, formation of a keel, elongation of the arm, solidification
and expansion of the sacrum, "locking" of the dorsal spine, closure of
carpal contacts into sutures or fusing of the elements, reduction of the
proximal metacarpals (I-III) relative to the fourth, elongation of the
fourth metacarpal and digit, lateral rotation of the scapulocoracoid and
thereby also the humeral glenoid (and why Dave's theory of the humerus
laying parallel to the trunk does NOT work), etc.. So far, no such animal
exists, including the "prolacertiforms," "protorosaurs," and any of Dave's
proposed ancestors. Even *Sharovipteryx* shows exactly the opposite of the
brachial modifications, getting SHORTER than the leg, with protraction of
leg elements, showing this is not even close enough to an ancestor to
counter the "ornithodiran" features. To date, however, many ornithodiran
synapomorphies, including the "s-curved" neck, have been over-ridden by
basal dinosauromorph taxa, even if one includes *Scleromochlus.*

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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