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Re: Eggs,Embyros, and Birds



Kari

    Subject #1)    Usually nests are preserved as individual items (as a
whole ['hole' :-)] ) containing several eggs - if you are lucky.
Oftentimes, all you have are filled-in depressions with scattered eggshells
within.  (The fill-in material is different from the layer containing the
nest (aka the hole) -  That's how we know that the nest exists).  When eggs
are found, even when some of the eggs are missing, you can usually tell
where the missing eggs used to be.  On a rare ocassion, you can find all the
eggs in situ, allowing an accurate count.  Different dinosaurs have
different egg counts per nest.  Some hadrosaurs may have had 18-22 eggs per
nest, while some theropods may have had only 2 (possible _Tarbosaurus_),
while others appear to have had 6-8 per nest.   Concerning the annual re-use
of the nests - this may be a function of the means of preservation.  For
example, Jack Horner's _Maiasaura_ nesting sites show that a catastrophic
mud-slide hit, burying 10's of thousands of the animals - yet the discovery
of new nests just slightly higher in the strata than the old nests indicates
that the animals came back to the old nesting sites.  I would imagine that
the annual use/re-use of nests would be extremely difficult to detect
without a similar incident (i.e. a catastrophe).

    Subject #2)    I personally think that birds are dinosaur descendents.
To me there are too many similarities for them all to be convergences.  The
detailed semantics of when do we stop calling them dinosaurs, and start
calling them birds, or make a new group that we call dino-birds - this to me
is where lots of people make their stand  (BADD or BAMM, versus BCF).  Of
course, we still have those who appear to have made it their own personal
crusade to prove that birds are descendants of other archosaurs (possibly
crocodilians), and not dinosaurs.  Oh, well, to each their own....


    Allan Edels


-----Original Message-----
From: KARI LYNN BAKER <Kari_Baker@ndsu.nodak.edu>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Saturday, January 16, 1999 10:50 AM
Subject: Eggs,Embyros, and Birds


>I am doing research, personal and for a seminar presentation, and I would
>like to hear everybody's views on these two subjects--
>
>
>
>Subject #1----
>
>How are scientists able to differentiate between the different egg
>laying
>> episodes?  Supposedly if these creatures (dinos) returned to the same
>> nesting horizion annually how are paleontologists able to infer how
>many
>> eggs were laid at one time?  They say that in each nest there is
>about 20
>> eggs for a hadrosaur, correct??
>
>
>Subject #2--------
>
>
>What are your views on birds being the descendents of dinosaurs??
>
>(I hope that I may get a variety of views on the subject, both supporting
>and opposing.)
>
>Kari Baker
>
>
>
>
>