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Hi Michael and list,

    My posting of last evening may have confused some persons by my
inserting, right at the beginning, that statement explaining why I doubt
that radial arrays of dinosaur eggs resulted from them falling out of a
vertical placement within a nest of vegetation that disintegrates and lets
them slowly fall into the radial array. (If included at all, it should have
been added at the end of the posting.  Sorry for the poor editing.)

    I probably should not have even brought that up, but just wanted to
offer the only other possibility (however improbable) I could think of that
might in some persons' minds account for the egg pattern.

    What I failed to make clear, Michael, is that in the actual situation
hypothesized, the eggs would have been radially placed while the egg layer
is located on the outside slope of the crater-shaped nest, upon a nest
for the eggs.  But, vegetation may afterward have been deposited atop them
to provide warmth (of decomposition?) and or as insulation from temperature
extremes caused by external sources such as the sun or weather.

    Such covering vegetation might then secure the egg positions in the
radial egg array.  And, I don't think the dinosaur would have much
difficulty producing such as array.  It would simply progress around the
nest's periphery a certain set distance for each successive egg.  The more
pointed end of the egg would simply slide down the gently sloping nest
'crater', gradually stabilizing by slight penetration into the looser sand
(or other type soil) that has naturally rolled back down into the nest
during the excavation process. If, to some listers, this radial laying of
eggs seems too
complicated a task for a dinosaur, consider the amazingly complex nest
accomplished by some types of modern birds.

    Concerning radial arraying of the eggs, wouldn't it be interesting if
the diameter of the nests of such precise egg layers turns out to be the
distance, say, from the animal's cloaca to the tip if its tail?
Conceivably, then, the egg layer could place the cloaca at the nest edge
('crater rim') while squatting just outside that edge, and if it did not
feel its tail crimped (but only just touching) against the opposite nest
rim, it would know it was laying the egg radially, without ever even looking
back (because its tail would be passing through a vertical line above the
nest's center.

    Michael, I hope this clarifies for you my speculative concept of how
eggs might be deposited radially from a position outside (but just on the
edge of) the nest.  I think I had you confused about what I was thinking.
Sorry.  My oversight.  Even in this scenario, the pubis might play a
stabilizing role for the egg layer.

    All this is, of course, purely speculation.  Reality may have been very
different.  I merely describe this scenario in order to show how radial egg
placement in a crater-shaped nest may have been very simple, even to a
'simple-minded' dinosaur.

    Yes, there are several other types of dinosaur nests and egg placement
patterns which have been discovered.  Each may have its own advantage to the
specific type of animal that produces it.  In the case of radially arrayed
eggs, so far as I recall, these are associated with theropods, but my memory
this could be flawed.

    Michael, you accurately observe that, "Also,in terms of temperature
control, this would seem to be a considerably more
delicate and complex arrangement in producing young than in other
dinosaurian contemporaries that seem to manage with simple unorganized
clutches, or laying eggs in rows of two, etc."

    Indeed, that is the way it seems.  It would be interesting to spend some
time looking for any correlations between dinosaur egg shapes, eggs-in-nest
arrangements, and egg layer types, with an eye toward the survival benefits
of different 'egg laying strokes' by different ' dinosaur folks'.   :)   It
is fun and stimulating to ponder the known facts and try to interpret their
significance, and the diversity of dinosaur nest habits is just one more
thing that makes dinosaur studies so challenging and (at least for me)
attractive.  It must be even the more so for you as a paleo artist.

    Now, I'd best sign off from this speculation before some figurative
sauropod egg (or gigantic theropod egg) gets hurled at me.

    Every good wish, and thanks for 'listening',
    Ray Stanford