Re: Breakable dino eggs - bigelow 2

[Crpntr@ix.netcom.com (Kenneth Carpenter)]

I wrote:
>
>> I agree, it is a problem that I have not satisfied myself with.  
>> However, we do know they did it.  They must have squatted, or 
> >kneeled back on their haunches.  Also, crocs and turtles sometimes 
> >cushion the fall of the eggs with their hind feet.
  

Bigelow responded:

 > Eyebrows very highly raised at this point...
 
>I must be missing something.  I thought it was common knowledge 
amoungst egg
>people that turtle eggs are some of the least calcified of the reptilia
>eggs. 


Partially true, different species show a range of shell types:
1.  Soft, parchment shell with little or no calcareous material (e.g.  
Lepidochelys kempi - sea
turtle).
2.  Semi-hard shell with a flexible calcareous shell that ranges from a 
poorly defined calcareous
crust, to discrete, loosely arranged, non-interlocking shell units (e.g. 
Chelydra serpentina -
snapping turtle).
3.  Rigid shell with a thick calcareous layer, with well defined 
interlocking shell units (Geochelone
elephantopus - Galapagos tortoise).


>The thin, 2mm-thick shell of ?T. bataar may indeed be illusory.

The consistency of  2+/- .05 mm shell for these eggs suggests that these 
are the correct thickness
and not illusionary.  

 > Perhaps the majority of the thickness of the shell was composed of 
elastic soft
>tissue. The calcite we see in the shell is what remains after the 
leathery
>part rotted away.

Yes, there was probably  a membrane on the underside of the egg called 
the egg membrane.  This
membrane is the site for deposition of the shell.  It is, however, thin 
in all extant egg laying
vertebrates and we see nothing to suggest otherwise in the fossils.



> We _still_ don't know much about how these T. bataar eggs were 
deposited.
>Since Carpenter doesn't buy the body incubation route for large dinos., 
that
>leaves vegatative fermentation as the incubation heat-source.   Now,
>although crocodyles don't use vegatative fermentation for incubation, 
they
>_do_ bury their eggs. 

Sorry, but Crocodilus palustris, C. johnstoni, C. niloticus, and 
Gavialis gangeticus all lay their
eggs in sand, gravel or other loose aggregate and let solar incubation 
occur.  C. acutus and C.
morelleti may use either a mound of vegetation or bury the eggs in the 
ground.   Alligator
mississippiensis, Caiman crocodilus, Crocodilus porosus, and Osteolaemus 
tetraspis all lay eggs in
vegetation mounds.  Alligator mississippiensis will urinate on the mound 
to begin decomposition
of the vegetation in order to generate incubation heat.