dino egg thickness revisited

[Phillip Bigelow <n8010095@henson.cc.wwu.edu>]

Regarding the discussion on whether the thickness of the ?T. bataar eggs is
a diagenetic feature or is original structure:

A 1992 paper by Karl Hirsch and Rolf Kohring (Jour. Vert. Paleo. 12(1):59-65)
describes some crocodillian eggs from the Eocene of Wyoming.  They note that
the fossil croc. eggs are 65-68 mm long, and 0.6 mm thick.  
>From some quick math on my part:
This thickness is _proportionally_ slightly over twice as thick as the
_proportion_ in the ?T. bataar eggs, if that is the true T. bataar
thickness.
  Hirsch and Kohring go on to say (p. 63) "Comparison of the shell thickness of
the Bridger <Wyoming> eggs to that of the similar-sized C. johnstoni eggs again
demonstrates that fossil eggshell can be thicker than that of comparable modern
eggs...the reason for this phenomenon is not known; it could be a primitive
trait."
  They noted no dissolution effects on the outer surface of the egg shell.  
Prisms and plates of calcite on the inner surface of the shell does, in
places, appear to be, in their words, "eroded".  They did not report any
evidence of pressure solution, either in SEM or in thin section.  In fact,
they noted a 0.1 mm-thick secondary diagenetic deposit on the outer surface of
the eggshells.
  The ?T. bataar eggshell may have experienced some degree of "telescoping" down
to a smaller thickness; however, this doesn't seem to be universally so with
all fossil eggs.  A blanket statement that dismisses egg thickness as anything
unusual is probably premature.
  The Sino-Canadian expeditions of 1987-1991 collected a lot of dinosaur
eggs. On a documentary of these expeditions, I saw dinosaur eggs, much smaller
than those of ?T. bataar, that had shell thicknesses roughly _1/4 inch_ thick.
Clearly, egg shell thickness has some bearing on the ecology of various
species of dinosaur.  It may relate to how the eggs were layed, buried,
or even incubated.  Shell thickness is not just a side-show curiosity.
  From personal experience, I have seen the effects of pressure solution on
fossil mollusk shells in thin section, and the pitting, embedded quartz
grains, and resultant neomorphism of prisms is unmistakable.  It should
be easy to resolve this discussion regarding the ?T. bataar material.
  <it would be interesting to compare the shell pore density on modern
crocodylian eggs, ostrich eggs, and the ?T. bataar eggs.  This may give us
some clue as to what the _relative_ embryonic metabolisms are for these
groups of archosaurs...at least, in my opinion>.  Oxygen uptake, you see...