Re: "Digging Dinosaurs"

["Allan Turner" <trexturner@hotmail.com>]

> I was just wondering myself that if these dinos
> did indeed lay their eggs in the "uplands", it seems there would be little
> chance for their preservation due to erosion,.....no???

What I'm going over here is better explained in "Digging Dinosaurs" but 
here's my understanding of the situation.  The Willow Creek anticline is 
part of what in Montana is called the Two Medicine Formation, sedimentary 
rock representative of an upper coastal plain from the Cretaceous.  It is 
rich with not only dinosaur egg remains but also baby and juvenile bones.  
There are, as discovered by Jack Horner and his crew in the late 70's and 
all through the 80's, nesting grounds -- nests on the same fossil horizon.  
Other upper coastal plains areas provided similar fossils and evidence.  
Formations representing the lower coastal plains, such as the Judith River 
Formation which dates to around the same time, did not.  Horner reasoned, as 
others had before him, that it was possible dinosaurs nested in the 
"uplands."  This made sense because the lowlands would have been too swampy 
for eggs.  This is true in another sense.  Lowland areas, which would have 
been similar to, say, Louisiana deltas (swampy) would have been too acidic 
for fossilization to occur.  To address your question re erosion in the 
uplands: well, the uplands, although admittedly more arid, were interwoven 
with rivers and streams which frequently flooded their banks, covering 
nesting sites with silt and whatnot from the highly volcanic Rockies to the 
west.  So whether it's the upper or lower coastal plains, both areas would 
be covered.  It's just that the upper areas provide conditions (less 
acidity) more favourable for fossils.  Of course, everything erodes and 
eventually those fossils will too, unless people like Jack Horner and his 
crew find and excavate them in time like they did in the Willow Creek 
anticline.  Now, what this means is that dinosaurs may very well have nested 
in the lower areas also.  And, as I've just read in a more recent book of 
Horner's, "Dinosaur Lives," there is evidence they did.  In the early 90's 
he excavated various nesting grounds -- in fact, whole complete egg clutches 
-- from seperate fossil horizons in the Judith River Formation.  The 
egg-laying culprits?  Lambeosaurs.  Why weren't these eggs dissolved?  They 
came from what appears to be an island of relative dryness.  So the question 
still remains.  Did dinosaurs nest only in drier areas or were the fossils 
from wetter areas simply not preserved?

Allan


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