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Re: live birth

On Wed, 8 Mar 1995, Jeff J. Liston wrote:

> > Since apparently no sauropod eggs have been found,  is it reasonable to
> > postulate that perhaps sauropods gave live birth?
> And Bill Adlam continued:
> >This has been proposed.  I find it hard to imagine it evolving: it would be
> necessary to go from big, calcified air-breathing eggs to much smaller ones
> before ovoviviparity and then viviparity could be possible.  Only then could
> large size at birth re-evolve.

> But what I have problems with, regarding the sauropods, and even 
> allowing that they may have laid the largest eggs that we currently 
> know about, is the sheer practical problems of being a sauropod 
> parent and NOT squishing your offspring that you have just expended 
> so much genetic energy producing.  Their eyesight would need to be 
> exceptionally good, given the size of the newly-hatched, to avoid 
> this as a very real problem. [Anybody got anything re endocasts of 
> sauropod optic lobes?]  

Why eyesight?  Couldn't they just carefully pick their way around by touch?
Or keep their distance from the nest?  Or as Stan said, they might have had
no parental care (I'm not sure if this makes a difference to the likely 
numbers and position of juveniles in herds).  Or if you like creative ideas, 
maybe the babies clung on or lived in pouches.  Or maybe they produced lots 
of offspring and just ate the ones they accidentally squished.

> So, you could say that maybe the sauropods just laid very big eggs, 
> producing large offspring that were above the 'Critical Size 
> Threshold'.

What's that?

[constraints on egg size deleted]

> Its a bit of a long way around, but it is what encourages me to 
> seriously consider live birth as a viable theory.

It's certainly a viable theory. Come to think of it, it could be that
viviparity evolved for other reasons and later enabled sauropodomorphs to
become gigantic.
                                                                Bill Adlam