Re: Paired Eggs in a Dinosaur Indicate Biological Sex

[Dann Pigdon <dannj@alphalink.com.au>]

Phil Bigelow 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).

Of course, many larger predatory birds (ie. raptors) are designed to be
able to carry quite a bit of extra weight. Compared to a fish or a
rabbit (or even a sloth!), a couple of eggs is nothing. Since predators
tend to have smaller populations than non-predatory species, anything
that increases the reproductive success would be an advantage.

Something small like a swift, on the other hand, that spends most of its
time in the air, and lives in huge numbers, would benefit more from the
weight reduction of a single egg on the go at any one time.

My two cents, anyway...

-- 
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Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.soffiles.com
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