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Re: Ouranosaurus' sail

>   but I was wondering if the sail of  Ouranosaurus, rather than a
> termoregulatory device, could have been a sort of mimicry, which rendered
> the inoffensive plant eater similar,  when seen at a distance, to a more
> dangerous spinosaur.

This has been suggested on-list in the past (by someone... I forget who...
:). Bill Clemens tells me that it has been suggested in-print for
Dimetrodon/ Edaphosaurus. In the latter case, this might serve as an
explananation for the difference in morphological complexity of the "sail"
among these taxa. It does seem possible that elevated dorsal spines, which
may in some cases be biomechanically favorable, may also be a common "theme"
in dinosaur display behavior. In the case of "high-spined" pairs, such as
Ouranosaurus/ Spinosaurus and Dimetrodon/ Edaphosaurus, I am more inclined
to attribute the display function to the herbivores, with the predator as
the mimic. It is also possible that there may have been some positive
feedback in the evolution of this feature in both species, with elevated
neural spines in the predators becoming a behavioral signal in that species,
and possibly a means of camouflage for isolated herbivores as outlined