Re: RE: Extinction

[grenard <grenard@herpmed.com>]

My own Common horned lizards (aka "horfny toads"_
P. cornutum eat at between 95 and 105.  In my personal
experience tgemperatures above 110 are lethal to horned
lizards and all other desert reptiles. The statement
that they wont feed at temps under 110 implies they will
live and be happy at 110 and above. This is simply not
correct.

If you read my posting on freezing in some amphibians and
reptiles, such as Rana sylvatica (The Northern Wood Frog)
you would have noted that I mention the existence of 
"cryo-protectants"  --- cryo-protectants (aka anti-freeze)
lower the normal freezing temperature of the solutions 
they're in. Thus  while you would expect the tissues and
body water of a turtle or frog (incl intracellular water)
to freeze at not very much under 32 F or 0 degrees C,
they do not.  While everything around their cells is
frozen including their tissues, the cells remain very
much nearly frozen but protected against freezing thanks
to cryoprotectants.  That these animals can survive
freezing temperatures by our standards is neither 
controversial or debatable. It is accepted fact. How they
do it is being studied and that work includes studying
cvryo-protectants liberated in response to inhospitable
thermal environments.

Desert species that evolved ways and means to deal with 
extremely high temperatures are far fewer than all other
species of amphibian and reptile which become stressed
and would die at temperatures over 90/95.  For most
desert species it is easily for them to protect themselves
against both very hot daytime temperatures and cooler
nighttime temperatures by simply digging into the substrata
or finding other insulated spots (e.g. under rocks, etc).
Reptiles thermoregulate by changing their position in the
environment of the moment because most cannot do it any
other way. It is all not that far fetched to theorize
that 50 foot dinosaurs would have a lot harder time doing
this compared to six inch lizards ... or even six foot 
lizards for that matter.