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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"?


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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