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Re: It's here...The Czerkas book

David Marjanovic (david.marjanovic@gmx.at) wrote:

<I've just found the description of *Jeholopterus*. There it says under
"Locality and horizon": "Daohugou, Ningcheng, Inner Mongolia, China. Lower
Yixian Formation; Early Cretaceous". According with this, "Etymology" says
"[t]he generic name is derived from the famous type specimen-bearing Jehol
group". Does it say in the *Pterorhynchus* paper why its authors disagree
on formation and age? Or don't they disagree, and the outcrop in that
place is so thick that there are two formations, Yixian above Daohugou?>

  The upper Yixian, with the Sihetun fauna, and the lower "Yixian", with
the Daohugou fauna, have been separated. I think the term Daohugou
Formation, as used in the *Epidendrosaurus* paper by Zheng et al. in
_Naturwissenschaften_ may be an error on some part, but its not like the
stratigraphy is resolved anyway in the Jehol Group. I disagree with
comments regarding the Daohugou sediments as non-Jehol as they are clearly
of a lithologic type confluent with those seen in the Yixian, Jiufotang,
and higher levels. However, seeing the lithology taken in hand should be
very interesting. Salamanders, insects and plants are also known from the
Daohugou, only recently recognized separately from the Yixian and
apparently underlying it in a close conformity. Meaning, it is probably
Tithonian in age.

  The Middle Jurassic (Dogger) statement of age probably stems from Li et
al. who hold that the Yixian in Late Jurassic (Malm), so the Daohugou must
be earlier; and this is the same Li who write on several papers with
Czerkas, so I am sure the Jurassic interpretation is being used here. I
agree with the Penn team and Xu et al. in that the age of this level is
probably earliest Cretaceous in age...


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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