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Re: [Re: Bird and dinosaur respiration]



"David Marjanovic" <david.marjanovic@gmx.at> wrote:
> > That's well said.
> >
> > But where to put in _Scipionyx_ with its diaphragm?
> 
> - Birds have a diaphragm somewhere. (Ref must be somewhere in
> www.dinosauria.com, can't find it now.) They just don't use it for
> respiration, AFAIK, and the abdominal air-sacs are located caudally of it.
> - Are you alluding to the hepatic piston system Ruben et al. assume?   >
Their _*ONLY*_ evidence for this, IIRC, is the "dome-shaped" outline of > the
liver -- well, the specimen is a 2-dimensional fossil; making     >  claims
based on the shape of organs that are flatter than in a        > roadkill is,
IMHO, rather unscientific.

+++++++++++++++++++++++

Actually they did have another, more solid (IMHO) piece of evidence, and that
was the lack of room in the specimen for posterior-dorsal (can't remember the
exact term) air sacs.

I have heard numerous retorts to the liver evidence, but no one ever talks
about the, apparent fact, that _Scipionyx_ didn't have room for air sacs in
its hind quarters. 

Jura



> - As someone has mentioned onlist, there is evidence against a croc-style
> diaphragm in *Scipionyx* -- its gut isn't limited to any part of the
> abdominal cavity. This can be affected by preservation, too, of course,
> unless the specimen has been compressed laterally enough.
> - This is older than the discovery of *Scipionyx*, but see for yourself
this
> older thread: http://www.dinosauria.com/jdp/misc/lungs.html -- if
> *Scipionyx* really would have had a hepatic piston system this would have
to
> be an autapomorphy.
> 


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