Re: Warm-Blooded debate

[Stanley Friesen <sarima@ix.netcom.com>]

At 10:31 PM 6/23/97 -0500, Michael wrote:
>  Crocs have functional four 
>chambered hearts, but the foramen of panniza is open during late 
>systole.  Even in crocs blood from the right systemic arch mixes with 
>that of the left.  If an animal had a high enough pressure too much 
>blood would mix and the animal would have a fulltime left to right 
>shunt with low O2 saturations. ...

I am not too sure that the crocs heart works like this.  I remember reading
somewhere that the foramen of panniza in crocodilians is pressure
controlled.  That is under one condition of differential pressure between
the systemic and pulmonary vessels it is held closed (by the mechanical
effects of the pressure), and under other pressure difference situations it
opens and allows cross-circulation.  This acts as an adaptation for long
dives.  (I wish I could remember which way it worked).

Moreover, the fact that this is a diving adaptation is, in itself, an
important point.  This means that any fully terrestrial archosaurs are
unlikely to have had this particular system.

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com