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Re: Ouranosaurus (but we saw a spinosaur?)



On Mon, 11 Mar 2002 10:53:23  
 Jonathan R. Wagner wrote:
>Dann Pigdon <dannj@alphalink.com.au> wrote:
>
>> Someone once mentioned on the list that spinosaurs may have evolved to
>> mimic ouranosaurs, in order to facilitate sneaking up on them. I've just
>> wondered whether the opposite could be true: that ouranosaurs evolved to
>> mimic spinosaurs in order to discourage predators.
>
>    I was one of those who have presented this idea on the list. It seems to
>recurr periodically, and was, at one point, put in print for Dimetrodon and
>Edaphosaurus (I have not yet tracked down the ref). At least in my
>formulation of the African dinosaur example, either could be a mimic of the
>other. In the Permian example, the argument could be made that, since the
>Edaphosaurus "sail" is more elaborate (with "cross-bars," etc.) and the
>Dimetrodon version is pretty simple, the latter is more likely to be a copy
>of the former. Still leaves one to wonder what edaph was using that thing
>for.

Hmmm...I doubt that _Dimetrodon_ used its sail to mimic _Edaphosaurus_, 
although there is no way I can discount it.  Recent studies by Bennett (I 
believe...I should check), using wind tunnel tests, seem to indicate that the 
elaborate bumps and bars of the _Edaphosaurus_ sail actually made the sail a 
better heat-dumping organ.  Various mechanical tests seemed to offer evidence 
for this hypothesis.  As for _Dimetrodon_, there is much speculation regarding 
its sail.    Certainly, _Edaphosaurus_, as a barrel-gutted herbivore, would 
likely have had an excess of heat to dump (due to fermentation and such).  So, 
Bennett's hypothesis seems reasonable.  Maybe _Dimetrodon_ evolved its sail to 
mimic the former, but I don't see any real evidence for it.

Steve

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