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Re: A delicate matter

The testes of birds are located deep within the body cavity, up against 
the vertebral column.  They are nestled among air sacs, through which 
inhaled air circulates on its way to the lungs (read up on avian 
respiration, if you are unfamiliar with their system).  The temperature 
of this air is well below that of the body temperature, and, under normal 
circumstances, it maintains the temperature of the testes at a level 
where spermatogenesis is possible.

I have no trouble imagining theropods with a similar system, especially 
the tetanurans, which, as GSP has pointed out (PDW), have rib cages very 
similar to those of birds, hence may also have had a similarly designed 
respiratory system.  A number of ornithischian rib cages are similar, 
although not quite to the same extent.  That may simply reflect their 
different body plans. 

Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu