[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Function Talks at Ostrom Symposium
On Saturday, February 20, 1999 12:33 AM, Stewart, Dwight
> How certain is it that dinosaurs WERE diaphragm breathers? And
> why would the transition
> forms (IF dinosaurs were diaphragm breathers) be selected for a
> diaphragmatic hernia?
1) Not too certain yet. Unfortunately, soft tissue remains are all we really
have for diagnosis, and this type of fossil is of course very rare. Ruben's
recent reanalysis of Scipionyx is a good study, IMHO, but not conclusive by any
means. You have to buy some plausible, but not 100% certain, assumptions.
2) Avian respiration requires air sacs connected to the lung, but posterior to
the diaphragm. Ruben's point is that you have to make holes in the diaphragm
to do this. Since croc-style respiration depends on creating pressure
differences between the anterior and posterior compartments (i.e. across the
diaphragm), placing any part of the respiratory system posterior to the
diaphragm would cause the whole system to collapse.