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Re: sauropods: homotherm,heterotherm or gigantotherm?
> > Plus I felt they just glossed over the heart
> > morphology of pythons and varanids in an attempt
> > explain why crocodylians have 4 chambered hearts
> > varanid & python hearts [possibly more species as
> > well] are functionally 4-chambered, and capable of
> > pressure separations equivalent to those seen in
> > mammals & birds).
--- David Marjanovic <email@example.com> wrote:
> How does that work?
Both groups have a muscular ridge separating a
majority of the ventricle. During muscular
contraction, this ridge meets the top of the ventricle
(bottom of atria) and forms a complete separation. The
result is a heart that is capable of achieving a
substantial pressure differential between pulmonary
and systemic sides, during each contraction. It makes
for a good example of how a 3 chambered heart could
become a 4 chambered heart.
Two years ago there was study done on ventricular
haemodynamics in _Python molurus_. The results found
the python was capable of producing systemic blood
pressure that was ~7 times higher than the pulmonary
side. That makes it, at least, as equivalent as the
pressure differential seen in humans.
The full ref for that is:
Wang, T. Altimiras, J. Klein, W. Axelsson, M. 2003.
"Ventricular haemodynamics in _Python molurus_:
separation of pulmonary and sytemic pressures." The
Journal of Experimental Biology. Vol. 206. pgs
I apologize if I wound up sounding harsh in the last
e-mail. I haven't had any appreciable sleep for the
past week. It seems to make me sound (er, write)
"I am impressed by the fact that we know less about many modern [reptile] types
than we do of many fossil groups." - Alfred S. Romer
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