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Re: Paired Eggs in a Dinosaur Indicate Biological Sex



Phil Bigelow (bigelowp@juno.com) wrote:

<It is interesting that a reversal back to a functional dual oviduct hasn't
occurred in living ground birds, but it has occurred in some living predatory
birds.  The pattern is confusing, and its relationship to flight appears weak
(at least to me).>

  All avian embryos and chicks apparently retain dual functional gonads;
development favors one (the left) over the other so that the right gonad and
associated tissues failt to develop to maturity and their tissues partially
resorbed. It is easy at this point to simply not cease function of the other
gonad during development. This speaks more for raptorial breeding than it does
for the suggestion of loss of one gonad for flight-related purposes. The ground
birds may have relegated tissue development to another region, or simply never
lost the restricted development of the gonads as a plesiomorphic condition.
This is unsurprising.

  Cheers,

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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