RE: FARCICAL: Extinction due to "blue balls"

["Jaime A. Headden" <qilongia@yahoo.com>]

Eric Martichuski (herewiss13@hotmail.com) wrote:

<B) If Birds have chromosomal sex determination, isn't it parsimonious to 
suggest that dinosaurs did too (or, at least, theropods)?  ISTM that such
a thing would be an _awfully_ big derived characteristic (if I'm using the
term correctly).> 

  Not really. A corrollary to this that is similar and probably
descriptive of the sex-characteristic is that birds do not become
endothermic until after they developed wings and flight, as indicated in
the histology of *Confuciusornis* (De Ricqlès, A.J.; Padian, K.; Horner,
J.R.; Lamm, E.-T.; and Myhrvold, N. 2003. Osteohistology of Confuciusornis
sanctus (Theropoda: Aves). _Journal of Vertebrate Paleontology_ 23(2):
373-386). While crocs have temperature-dependant sex change, and modern
birds do not, this does not tell us that all animals leading to birds that
weren't crocs, including dinosaurs, were not temp-dependant ... it only
tells us that the change in birds, or the change in crocs from a primitive
and likely temp-based condition, changed in one of these lineages.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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