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Re: Theropod "migrations"



Larry Febo wrote:
----- Original Message -----
From: Larry Febo <larryf@capital.net>
To: Jaime A. Headden <qilongia@yahoo.com>
Cc: <dinosaur@usc.edu>
Sent: Saturday, April 24, 1999 7:31 AM
Subject: Re: Theropod "migrations"
               (Snip)

> So the here you are saying there was a "Bering Land Bridge" in the late
> Cretaceous. Admittedly, my knowledge of ancient geology and continental
> positions are not up to par, but, that`s why I consulted the web site
> located at: http://vishnu.glg.nau.edu/rcb/Late_Cret.jpg
> which , admittedly, dosen`t show the portion of the globe we are
interested
> in, but I can`t see how the Bering land bridge could exist that early. I
> mean, the N American continent had a lot of westward travelling to do
> (relatively speaking) to close that gap no? I (of course) may be wrong
here.
> I`ll have to look into it further.



Well, I have looked into it further. Evidently, most of these "diagrams" you
see in both popular science texts, and on the internet, don`t amount to much
for detail. I did an extensive search on "Bering Land Bridge", and after
about 20 pgs of nothing but the Pleistocene connection, gave up. But, on
looking into Cretaceous Dinosaurs, had better luck. It seems there was an
1992 International Conference on Arctic Margins whose Proceedings are posted
on the internet at: http://www.mms.gov/itd/pubs/1994/94-0040/toc2.htm
(takes a long time to download articles). Greg Paul had written an
interesting article on "Physiology and Migratio of North Slope Dinosaurs".
But the article that I found relevant by Louie Marincovich titled "Earliest
Tertiary Paleogeography of the Artic Ocean" shows that (by analysis of
mollusk fossils in the Prince Creek formation) it is determined that the
Arctic Ocean Basin was almost completely isolated from the World  Ocean
during the Late Cretaceous, only opening up a passage to the North Atlantic
in the Paleocene. and..."The accretion of tectonic plates between Asia and
North America largely closed any connection between the Pacific and Arctic
Oceans by the late early Albian (ca 105-110Ma) (Wialliams and Stelck, 1975).
So......I guess there could have been a Cretaceous Bering land bridge after
all.




>But what about all the other areas that
> Oviraptors and Velociraptors have gotten into? Could land bridges have
> developed there as well?? How?....I can see possibly between North and
South
> America, due to the subducting plate causing a string of Andean volcanoes
> but what about Africa at that time, ...What about Australia???
>


I`m still not sure how isolated these other large Continental land masses
(formerly Gondwana were in the late Cretaceous). They certainly look
isolated on the diagrams, but I admitt now, they will need closer scrutiny
to determine if I really have a case for BCF.