> 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)? Bearing that latter proviso in mind, some sharks, fish
> (sensu very loose indeed), frogs, reptiles of various persausions (or
> sauropsoids), scorpions... Various lineages have manged this, but
> archosaurs seem uninterested in such experiments.
>
> My suspicion is that the hard and potentially sharp eggshell shards may be
> a
> discouragement, but it's no more than a suspicion.
As I recall, sauropterygians are considered to be archosaurs (correct me if
I'm wrong here) and ichthyosaurs managed to give live birth well enough.