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Re: [cold-blooded dinos (revisited)]



UNION4884@aol.com wrote:
> Hi all,
> Sorry to bring this topic up again. I recently asked for  information about 
> the current "conventional wisdom"  with regard to the cold- or 
> warm-bloodedness of dinosaurs.  I  received some excellent replies (which 
> corresponded with my reading).  They  generally expressed the opinion that  
> some dinos were probably endothermic, some ectothermic, and some in-between 
> (had some ability to regulate temperature). .  
>  
> However - this week, as I was catching up on my pile of Science News 
> magazines -  I read came upon a discussion of an article by John A. Ruben et

> al.( the article was published  in the January issue of Science).
> 
> Ruben and his colleagues (who are physiologists)  examined a fossil of 
> Scipionyx samniticus,  a small meat-eating theropod.  They think the fossil
- 
> which has traces of internal organs - shows that the diaphragm was used for 
> breathing (like in mammals).   However,  Ruben et al.  state  that dinosaurs

> (S. samniticus included) are cold-blooded.   In addition, James O. Farlow -
a 
> paleontologist - is  quoted as saying that dinsoaurs were cold-blooded, but 
> that theropds were "as active as" warm-blooded animals.  These scientists 
> (apparently) categorically state that dinosaurs were cold-blooded; they
don't 
> even tip their hats (so to speak) in the direction of any other theories.  
> 
> Any thoughts?  (I want  to put the most current information into my dinosaur

> book for  kids).  
> 
> Thanks,
> Barbara Saffer
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Right now it very much a matter of preference. Do you prefer deinosaurs being
endothermic or ectothermic? 

Both sides have plenty of evidence for each case, making this debate a very
long running stale mate.

As for a diaphragm and active lifestyle being a problem for the ectothermic
side, it really isn't. Crocodylians have diaphragms and there are plenty of
active ectotherms (e.g. varanids & lamniform sharks).

If I were you I'd try and keep the book as objective as possible. Try and
present both sides of the debate as best you can and let the reader choose
sides (I'm assuming this would be what you were going for anyway).

Archosaur J


Jurassosaurus's Reptipage: A page devoted to the study of the reptilia

http://members.tripod.com/~jurassosauridae/index.html

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