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Re: Bird and dinosaur respiration



> 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.
- 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.