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Re: pterosaur crest extensions



David Peters (davidrpeters@earthlink.net) wrote:

<In Pterorhynchus, Germanodactylus and Tapejara a number of workers have
shown that the premaxillary crest is extended dorsally by soft tissue, but
in Tupuxuara, Thalassodromeus, Dsungaripterus and Phobetoropter, to name a
few, no such extensions have been indicated.
 
  Why not?>

  The answer is apparently the mode of preservation: 3D versus
compressed-slab preservation. The the former, some specimens of *Tapejara*
have been preserved on slabs where it is the slab that shows the crest; in
other specimens, prepared-out specimens from limestone nodules do not show
any crests or traces. Depends on the region of preservation likely, where
clay nodules form alongside shore or in stream- or riverbeds, and thus
tend to preserve in 3D, whereas animals that drop into the lake a bit out
from shore appear to miss the clay and get piled under silt or sandstone,
and get compressed in the typical lagerstätten. The limestone--clay
nodules are still part of the same depositional sequence as the flattened
sandstone--limestone plates, just regional based on depositional location.

  Likely, as in skulls Chris Bennett has described for *Germanodactylus*,
the bony crest was extended by a keratinous one some distance from the
skull. I don't think shape of the crest has anything to do with extent,
and so far, no pterosaur seems to show where a taller bony crest might
mean taller keratinous crest. But, it should be there nonetheless.

  And as an aside, "Phobetoropter"?

  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.

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