RE: Dinosaur whodunit: Solving a 77-million-year-old mystery

[Dann Pigdon <dannj@alphalink.com.au>]

Good points. 

I suppose I was thinking about how the eggs would behave while loose on a 
substrate. Many 
ground-nesting birds that have little in the way of a nest (plovers and terns 
come to mind) tend to 
have very cone-shaped eggs to help them stop rolling away (instead they just 
roll in a tight circle). 
While rolling loose on a slight slope, they'd tend to some to rest 
blunt-end-down.

Embedding the eggs in a substrate would negate any such movement, which begs 
the question; 
would non-avian theropod eggs have had to be turned at any point? I imagine 
that modern birds 
that bury their eggs (like Mallee fowl or scrub turkeys in Australia) probably 
can't turn them. Are 
eggs that must be turned periodically something unique to avians?


Quoting Dino Guy Ralph <dinoguy@sbcglobal.net>:

> Dann Pigdon writes:
> 
> "The illustration has the pointed ends of the eggs facing down-slope.
> Wouldn't the opposite be more stable?"
> 
> You would think so, but there were undoubtedly other considerations, for
> this is how they were found in this specimen, and this is consistent with
> _Troodon_ egg clutches from Montana as well as small theropod clutches in
> Mongolia.  The following are a few of the advantages that such an
> orientation may have conferred.    
> 
> 1) For one thing, it would be easier to lay an egg pointed-end-first, as
> this would require minimal dilation as the egg first begins to emerge.  This
> is how kiwis lay their eggs, as you can see in x-rays.  In this scenario,
> the eggs need not have been inverted by the mother after being laid.  
> 
> 2) If the substrate was sufficiently compliant, the pointed end would have
> been more readily planted than the rounder end, and it would have been
> better suited to holding its position.  The impression of each egg's shape
> in the mound surface may have helped to keep each egg in its place, but any
> insertion of the pointed tip into the soil would have provided an extra
> measure of security.   
> 
> 3) The rounded end of each egg would have been better able to support its
> share of the brooding parent's weight than the pointed end.
> 
> 4) The rounded ends of the eggs would have been more comfortable for the
> brooding parent to rest upon than the pointed ends.  
> 
> I'm no authority on the subject of dinosaur nesting behavior, and I hasten
> to point out that there was a diversity of egg shapes and clutch
> arrangements among non-avialian theropods.  These caveats aside, I have no
> trouble seeing advantages to the pointed ends of the theropod eggs in
> question facing down-slope, however counterintuitive this orientation might
> appear to be. 

-- 
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Dann Pigdon
GIS / Archaeologist              http://geo_cities.com/dannsdinosaurs
Melbourne, Australia             http://heretichides.soffiles.com
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