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Re: Pubic Openings (Egg Sizes)



Martin Human wrote:
> 
> Dann Pigdon  wrote...and  Matt Fraser wrote...(much discussion about
> eggs versus pubic sizes etc snipped):
> 
> Isn't it perhaps simplistic to use pubic size (limited in some
> dinosaurs, it has been mentioned) as an indicator of the ability to lay
> eggs of a certain max diameter, when we know (sorry, no references here)
> that  mammals when giving birth, and (some/all?) birds when laying eggs,
> are subject to significant distensions of pubic openings due to the
> actions of certain hormones designed to facilitate this etc?
> 

        Even given a certain amount of flex in the public bones (which
I doubt, dino pubes appear to be fused together at the ends), the
maximum size of an egg that can pass through the opening of the
largest dinos is still quite small relative to the creature's size.
If you look at the rear view of Greg Paul's tyrannosaurus skeletal
reconstruction in PDW you can see how small the pubic opening was
compared with a 4-6 tonne creature. The same is true for his
Hypacrosaurus (Corythrosaurus?).
        Does any one know what size the pubic opening of
pachycephalosaurs was? I seem to remember Homalocephale having these
strange caudal ribs just behind the pubis that widened that part
of the tail. Could pachies have been vivaparous? I'm not sure that
very much postcrania are known for most of them.

-- 
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        Dann Pigdon
        Melbourne, Australia

        Dinosaur Reconstructions:
        http://www.geocities.com/capecanaveral/4459/
        Australian Dinosaurs:
        http://www.alphalink.com.au/~dannj
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