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RE: Reptile-Bird-Dinosaur-Penis Connection

-----Original Message-----
From: Ben L.

(mass snippage below)
  Most male reptiles have some sort of penis-like
structure(s) for internal fertilization.  Male birds
lack such an organ and only use a cloaca kiss.  
 I'm only in a high school biology AP class, so my
reasoning and information may not be all correct.  So
I'm posting these hypothesis on the List -- would the
experts take a look and see if my thinking makes any
sense?  Thank you.


Your reasoning isn't too bad, some of your info (I believe) isn't quite
right because some male birds do retain a penis.  These birds include
ostriches and ducks, among others.  This seems to indicate a relationship
between flight and the presence or absence of this structure.  It is also
interesting to note that large terrestrial reptiles (including birds like
the ostrich) generally have larger males members than females.  You can see
it in crocs and ostrich.  Why would volant birds have larger females?

The answer may lie in flight.  Birds that can mate on the wing with a
"cloacal-kiss" can afford to have smaller males than females, may actually
require it.  The female needs to be bigger because of the eggs she
carries--she must be strong enough to carry the added load.  Males, lacking
such a need, are able to be smaller.  Ostriches, which must mate on the
ground, have larger males than females.  This makes sense too, if you cannot
easily coordinate a cloacal-kiss (rather difficult on the ground) and are
going to have to implement a penis, you want the male to be larger. 

Actually, this has been my argument against always suggesting that the
larger morph of theropods was the female.  It doesn't hold for terrestrial
birds and if you look at crocs, you see the same thing.