Re: Fossil Synapsid Eggshell

["K and T Dykes" <ktdykes@arcor.de>]

<<While fossil sauropsidan eggshell is pretty well0understood and studied, I 
am unaware of fossil synapsid eggshell, from basal synapsids like 
ophiacodonts up through extant taxa like monotrematans. Does the 
calcification level of synapsid egg lend itself to fossilization, and if so, 
are there references describinbg the existence of said eggs and the process? 
Any help would be appreciative.>>

The only extant egg-laying synapsids, ie. monotremes, produce 
parchment-shelled eggs.  To me, this suggests they're descendants of 
parchment-shelled egg-layers.

Interesting discussion on synapsid eggs and the evolution of lactation can 
be found in:

Oftedal OT (2002a), The mammary gland and its origin during synapsid 
evolution, Journal of Mammary Gland Biology and Neoplasia, 7(3), p.225-252.
Oftedal OT (2002b), The origin of lactation as a water source for 
parchment-shelled eggs, Journal of Mammary Gland Biology and Neoplasia, 
7(3), p.253-266.