Re: Mosasaur babies

[John Bois <jbois@umd5.umd.edu>]

On Tue, 8 Jan 2002, Mike Everhart wrote:

> All three lineages were very successful in
> their return to the sea.... maybe being able to give live birth was a
> critical step in their success.....

I think this is the bottom line: body plan adaptations for sea compromise
the ability to incubate (or even just to lay!) eggs on land.  Live
birth--or the ability to evolve it--would seem to be a prerequisite for
fully sea-going life.  I note the fab adaptations of penguins to catch
fish,
but, at the same time, their compromised ability to hide nests (i.e., they
can't fly).  It is reasonable to suggest this is a limitation on their
distribution (along with the presence of cold current productivity).  It
is also interesting to note the _absence_ of live birth in these
species--surely this would be an important advantage...I don't think
anyone is suggesting that the evolution of an effective delivery system to
the embryo is an easy trick.  But, the total absence of any known
archosaur viviparity, suggests, rather strongly, that they are stuck with
eggs.