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Re: Psittacosaurus bristles



Stephan Pickering (stefanpickering2002@yahoo.com) wrote:

<A thorough analysis of the structures was published, with photographs, by
Gerald Mayr. Gerald Mayr, D. Stefan Peters, Gerhard Plodowski, Olaf Vogel,
2002. Bristle-like integumentary structures at the tail of the horned
dinosaur Psittacosaurus. Naturwissenschaften 89(8):361-365.>

...

<What do "these things" mean? The paper gives one the likely indication.>

  Actually, Mayr et al. are not very certain what these are aside from
integument, and forward their opinion that these have nothing to do with
avian integumental structures. That some of the structures appear to touch
bone is possible evidence of dermal displacement in the carcass, but this
is not discussed, and the authors sorta ignore the possibility of shifting
of the skin around the carcass during the deposition process, which would
result is a problematic relationship of "bristles" to bone. They indicate
a relationship of bristles to the dorsal line of the tail based on
apparent origins for more elements, and the orientation of the tail.
Histological sections, which would be ideal, have not been performed. To
quote from the paper (pg. 354):

"If the "bristles" of *Psittacosaurus* can be shown to be homologous to
the filamentous structures of theropod dinosaurs, similar structures may
have already been present in a more comprehensive clade including
ornithischian dinosaurs. At present, however, this conclusion would be
premature and more detailed investigations on the microstructure and
biogeochemistry (Schweitzer et al. 1999; Schweitzer 2001) of the
integumentary structures of Psittacosaurus and theropod dinosaurs need to
be carried out. Without further evidence, there remains the possibility
that the "bristles" of Psittacosaurus are greatly modified scales, as has
been suggested by Reisz and Sues (2000) for the - structurally different -
appendages of the Triassic reptile *Longisquama*."

  The paper itself, as acknowledged by the authors, is a very preliminary
report offered because of the increased interest and debate caused by the
specimen, despite the fact that ownership was under dispute. We may not
see more if and when the material comes under the provenances of the
Chinese. Junchang Lü has already done work on pterosaur integument and it
is possible he will be able to further research on this if it comes to
China ... soon.

  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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