Re: Sinornithosaurus millenii

["Jerry D. Harris" <LOKICORP@compuserve.com>]

Message text written by INTERNET:ofsosa@uclink4.berkeley.edu
>Does this clinch it or what?  How could anyone argue now?  We
predicted the closest relatives purely by morphology, and now it
is confimired.  The essence of predictability.  I'm stunned.<

        I myself find the evidence for a theropod origin for birds is the
most compelling out there, but as a scientist, I must always be open to
alternative options!  "How could anyone argue now?"  Well, future fossil
discoveries _could_ show that dermal structures homologous to those on the
Chinese theropods are a _primitive_ condition for a larger group of
archosaurs -- say, the Ornithodira.  This would mean _all_ dinosaurs
(including ornithischians) primitively possessed dermal structures, but
some have subsequently lost them.  If (and this is a big if, still)
structures like those on _Longisquama_ are homologues with the Yixian
"fibers," then this may be the true interpretation...it would mean that we
have a biased view of dermal structure distribution because we haven't
found ornithischians from the Yixian (or any other formation) with a
similar degree of preservation.  If someone should find an ornithischian
with dermal "fibers," then we can no longer say that only the Theropoda
possessed them and that birds _must_ have stemmed from theropods using the
dermal structures as the linking apomorphy.


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                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 899-2809
                  Fax: ; (505) 841-2866
               102354.2222@compuserve.com