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RE: Psittacosaurus bristles

On Thu, 14 Nov 2002 15:28:56  
 Daniel Bensen wrote:
>Thanks for the clarification.  So Psittacosaurs (at least of this
>species) did indeed have bristles, which may or may not have simply >been 
>elongated scales (if they actually did touch the vertebrae, >the spines would 
>have to be bone, themselves, wouldn't they?  But >they sound too flexible to 
>be bone) or may have been some type of
>dinofuzz/protofeather, which means that that sort of integument >either 
>evolved twice or is primitive for all dinosaurs, if >secondarily lost by many. 

Well, I would hold off on saying that all _Psittacosaurus_ species possessed 
these strange bristles, just because there are so many species known, and they 
vary both in geography and in time.  Also, this guy with bristles has been 
designated _Psittacosaurus sp._, mostly because the skull is in ventral view 
and crushed (IIRC what HP Holtz said a few months ago).  Actually, it appears 
as if the specimen really is quite distorted, and that causes problems with 
both a species designation and with trying to determine exactly what these 
structures are.

>I like HP Jansma's cricket idea.  African porcupines _do_ use their
>spines to make noise (some of the spines are especially adapted for >this 
>purpose).  Good old sexual advertisement is another possibility.

It's a nice sounding idea, but who knows?  I hate speculating on possible 
functions of structures, but if the preliminary reconstructions provided by the 
authors are correct, these structures might have been some sort of defensive 
adaptation.  The reason I say this is that these bristles appear to parallel 
the ossified tendons seen in some _Psittacosaurus_ specimens.  This was briefly 
discussed onlist this summer, but the fact that both ossified tendons (which 
indicate a strengthened back/tail) and bristles are known at least makes it 
possible that they were some sort of defensive structure.  

Of course, we have one crushed specimen that has only been preliminarily 
described.  All of these functions are possibilities, but we simply can't tell 
for certain.  


Stephen Brusatte
Geophysical Sciences
University of Chicago
Dino Land Paleontology-http://www.geocities.com/stegob

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