RE: Function Talks at Ostrom Symposium

["Stewart, Dwight" <Dwight.Stewart@VLSI.com>]

> -----Original Message-----
> From: Augustus T. White [SMTP:augwhite@neosoft.com]
> Sent: Saturday, February 20, 1999 2:42 PM
> To:   'Dwight.Stewart@VLSI.com'; 'EctoDino@aol.com'; dinosaur@usc.edu
> Subject:      RE: Function Talks at Ostrom Symposium
> 
> 
> 
> On Saturday, February 20, 1999 12:33 AM, Stewart, Dwight 
> [SMTP:Dwight.Stewart@VLSI.com] wrote:
> 
> [snip]
> 
> >        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?
> >
> >     Dwight
> 
> 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.
> 
>   --Toby White
        [Stewart, Dwight]  
        @@@@@@@@@@@@@@@@@@@

           Thanks Toby.  Having read the replies to this & due to the fact
that my Maint guys
        are busily disassembling a torordial orifice ATT,  I am wondering
about what Allan
        proposed.  By that I mean, perhaps some transitional structure could
have developed
        that would allow preforation of the diaphragm in such a way that
breathing could
        still be accomplished.  We do this with a slit valve in controlled
pressure systems
        all the time.  Basically, a biological slit valve system could be
fairly easy to evolve.
        One simply needs a axis that can allow apperture of a reasonable
degree, a power
        source (pneumatic works fine) and a sealing surface for the baffle
to fit into when
        the slit valve is closed (and thus sealed).  Nature uses
differential pumping in other
        organs, why not the pulminary?  Of course, this (too) is
speculative.  Since I think
        nature normally comes up with ideas a tad ahead of us, I wonder if
there isn't
        an extant animal out there that uses this method of breathing?

        Dwight