Re: Sheesh

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "K and T Dykes" <ktdykes@arcor.de>
Sent: Tuesday, October 24, 2006 9:32 PM

> Why have no birds, or indeed -as far as is known- archosaurs (sensu sort 
> of
> traditional) never got around to giving birth to live young (sensu any way
> anybody chooses)? [...]
> My suspicion is that the hard and potentially sharp eggshell shards may be 
> a
> discouragement, but it's no more than a suspicion.

This could obviously be solved by evolving a soft shell (and then abandoning 
it altogether). The textbook explanation (...assuming there really is a 
textbook that mentions this question!) is that because archosaurs store the 
calcium the embryo needs in the shell and not in the yolk, the hard shell 
can't be abandoned, but I have no idea how testable this really is. It 
certainly sounds neat, however.