Re: Warm- vs. Cold-blooded Dinos

[Alan Geralnick <alang@tecsun1.tec.army.mil>]

Forgive a rank amateur and list newbie for just jumping in to the 
debate but is so good I couldn't resist.

Intuitively I believe almost all the dinosaurs were warm-blooded for 
several reasons:

While the climate of the time may have been milder than it is today, 
there were still polar regions and mountains.  These regions would 
have quickly been dominated by warm-blooded animals.  These active 
animals would then begin to spread into the warm regions where their 
increased activity levels would allow them to establish themselves 
and, as we see in the fossil record and around us today, dominate 
there too.  The success of the dinos argues for this.  I don't 
remember hearing of any increased numbers of mammals in the polar 
areas.  If the dinos didn't do it the mammals would have.

The other argument is the dino tail.  Holding a large tail off the 
ground for long period is an enormous energy drain.  Even if the 
dinos were active for only short periods each day (like reptiles) 
they would have had to generate large amounts of sustained energy 
output to hunt or forage.  I can't imagine a reptile making that kind 
of energy trade-off, only a bird or mammal.

Alan

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 From: Alan Geralnick           U.S. Army Topographic Engineering Center
Phone: 703-355-3189             ATTN: CETEC-OD-DT
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Email: alang@tec.army.mil       Alexandria, VA  22315-3864
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