RE: stegosaur

[Crpntr@ix.netcom.com (Kenneth Carpenter)]

You wrote: 

>
>>Yes, because both Stegosaurus stenops and the smaller plated 
Stegosaurus 
>>armatus occur in the same fossil deposits (e.g. Marsh-Felch Qaurry).  
>>Also, the paleoenvironment of the Chinese sites are similar to that of 
>>the Morrison Formation - i.e. semi-arid, seasonal rain fall. Therefore 
>>the thermo regime was similar for the various stegosaurs.
>>
>>The vascularized plates simply mean that abundant blood was available 
to 
>>the plates and would allow them to "blush" in display.
>>
>Thank you for the clarification.
>
>"Blushing" in display is of course well known for some birds with areas 
of
>vascularized bare skin (honeyeaters of the genus Melipotes come to 
mind).
>However, I am still not entirely convinced.  Even if the primary 
function of
>the plates was display, their vascularization would surely have caused 
them
>to have, at least passively, some thermoregulatory effect (indeed I am 
not
>sure how S. stenops could have avoided this unless there was some
>complicated shunting mechanism involved). Further, African elephants 
(which
>occupy an extremely wide range of thermal regimes) use their ears both 
for
>display and thermoregulation, despite the fact that Asian elephants 
have
>much smaller ears (in fact a palaeospecies of Elephas coexisted with
>Loxodonta africana at Olduvai, though of course we don't know how big 
its
>ears were).  Is it at least possible that there were behavioural 
differences
>among sympatric stegosaurids that may have had thermoregulatory 
consequences?
>--
>Ronald I. Orenstein                           Phone: (905) 820-7886 
(home)
>International Wildlife Coalition              Fax/Modem: (905) 569-0116 
(home)
>Home: 1825 Shady Creek Court                  Messages: (416) 368-4661
>Mississauga, Ontario, Canada L5L 3W2          Internet: 
ornstn@hookup.net
>Office: 130 Adelaide Street W., Suite 1940    Compuserve ID: 72037,2513
>Toronto, Ontario Canada M5H 3P5             
>
>
>


The fact that both species of Stegosaurus in North America co-occur in 
the same fossil sites (e.g. Marsh-Felch Qaurry; and Quarry 13, Como 
Bluffs, WY) demonstrates that they did indeed live at the same time.  
Since they apparently shared at least a part of their biogeographical 
ranges, then I would have to argue that they were indeed subjected to 
the same thermal stress.  I am sure that there was behavior segregation 
of the species, but that is not the same as habitat segregation.

As for Huayangosaurus, the sediments of the Lower Shaximiamo Formation, 
in Sichuan Province, China, indicate seasonal rainfall and semiarid 
climate.  This is similar to that of the Morrison, therefore, I would 
suspect that the thermal stress on Huayangosaurus was close to that of 
the two species of Stegosaurus.

Your suggestion about "look how big I am" is display (threat to be 
exact), which was one of my two hypotheses for the plates (the other is 
species recognition).  The cat analogy is one that I used in a 
manuscript were I discuss all of this submitted to the Morrison 
Symposium volume (to be published as a GSA Special Paper early next year 
- knock on wood).