Re: egg meanderings while on cough medicine

["Tony Canning" <tonyc@foe.co.uk>]

On May 23, 10:56am, Betty Cunningham wrote:

> Subject: egg meanderings while on cough medicine
>
> Have any bird or bird desendants EVER developed live-bearing?  Do we
> have any fossil clues from any post K-T period that they may have
> developed along those lines in an early non-flight form?  I don't
> think so, but if the abdomen allowed for more room for a retained
> egg or juveniles from a period were examined for wear and tear as
> much as Miasaur juveniles have been, what would be the fossil
> results?
>
> Therapods should probably parallel birds in the egg-laying
> department, but the devisions of ceratopians and sauropods and such
> from therapods were just how many millions of years before the
> devision of birds from therapods (or therapods from birds)?  Why
> would all dinosaurs be dependant on egg-laying?

This is a bit tangential, but if you look at a major group of modern
diapsids, snakes & lizards, you find live-bearing has evolved many
times.  However, phylogenetic analysis of reproductive strategy shows
that live-bearing has probably NEVER evolved from a species which
guards its eggs.  This is true even where egg-guarders and live
bearers are close relatives. There are other explanations, but this
suggests to me that live-bearing brings no increase in fitness over
egg guarding in this diverse group.

Given that egg guarding is present in birds, crocs, Oviraptor, it
seems reasonable to assume that egg guarding is an ancestral archosaur
characteristic.  So maybe live-bearing never evolved because it would
have brought no evolutionary advantage, ie. fitness might have
decreased.

> Why does size of a saurapod mean live-bearing?  What am I mising
> here?

I didn't understand this either - if there is evidence of live-bearing
sauropods, could somebody explain please?

> Betty Cunningham
>-- End of excerpt from Betty Cunningham

Hope you feel better soon Betty..

Tony Canning
tonyc@foe.co.uk