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_Scipionyx_ and diaphragms again



I was recently looking over the original _Scipionyx_ monograph along with
Ruben et al's Science paper regarding a possible diaphragm in the little
bugger and I was wondering if it has actually conclusively been resolved
one way or another with regards to the diaphragm issue.

I remember that HP Jeff Poling had a page up on his site that featured a
compilation of different DML postings rebutting Ruben's paper, but I can't
seem to find it on the site anymore.

Anyway the majority of the posts seemed to focus on the lack of pubic
mobility in theropods, thus casting doubt on the hepatic piston scenario,
yet I don't remember anyone mentioning anything about the dorsally placed
colon eliminating the chance of posterior air sacs in the animal. Nor do I
remember much talk about the more anteriorly placed guts (relative to
birds). Mostly it was just talks about pubic motion and a shovel crack
giving the false representation of a diaphragmatic split.

That and the lack of lumbars in theropods.

Now my memory's not the best so I could have just missed it the first
time. A link to the page would be nice.

In regards to said diaphragm, Ruben et al only state that it would ASSIST
in providing increased ventilation during bouts of high aerobic activity.
With this in mind, could it not be possible that the diaphragm was
present, but was very simple in construction. Since it would then only
come into play during intense excercise, the evolution of the avian
air-sac system wouldn't pose as much of a problem (i.e since it would not
be the primary ventilator, a puncture through it would be less of a
detriment).


Oh and one final thing. What evidence do we have that theropods had an
avian respiratory system. What osteological markers were there? I mean the
pleurocoels would work fine just as weight reducers. Do we actually have
evidence that they played a part in respiration?


Jura

Jurassosaurus's Reptipage: A page devoted to the study of and education on,
the reptilia:

http://reptilis.net

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