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 From:  GSP1954@aol.com[SMTP:GSP1954@aol.com]

>Rapidly dumping body heat into the cool night sky is easy. Just flush the
>skin with blood from the body core until the heat is unloaded. In the daytime
>minimize heat gain from the environment by minimizing blood flow to the body
>surface. Giant tropical mammals do it every day, and the bigger the animal
>the better it works. 

There are only a very limited number of ways to "store" heat - elevated
temperature, phase change or chemically.    Since elephants don't have
boilers or reversable chemical means to store heat (and it seems
unlikely that sauropod did either), this almost certainly means that
their core body temperature becomes elevated during the day (due to
internal sources, as well as some heat absorbed through the skin, even
with restricted bloob flow).   Then, your flushing process would
presumably "dump" the heat by lowering the core body temperature.

A large mass, like an elephant can absorb a lot of heat with a small
temperature elevation.  However there must be an elevation.

So you'd expect that core body temperature would rise during the day,
peaking in the late afternoon, and then drop during the night.   Has
this been measured?   I would presume so, because it would be the only
direct way to confirm the mechanism you describe.  I'd be interested in
a reference or some way of finding out the magnitude of the swing.

Another way to say that they are only homeotherms if you average over a
24 hour period.   Of course, the deviation might be fairly small, but it
is still the case.