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Re: 1st Inland sea incursion



In a message dated 1/2/99 2:58:24 AM Eastern Standard Time,
DINOBOY@worldnet.att.net writes:

> 
>  During what age did N.America first experience an incursion by a sea and
>  from which direction ?I

The incursion of the Western Interior Seaway was not an overnight affair.
Based on several sources, the production of the seaway probably took over 20Ma
to finally separate eastern and western North America. Formation of the seaway
was underway probably before the Apian with transgression apparently
proceeding southward out of Artcic  Western Canada through the Early Aptian.
As sea levels continued to rise this was followed by transgression in a
northward direction from the Gulf region. It appears that the seaway was
complete by the end of the Albian.
So in essence North America was contiguous until late in the Albian. Therefore
there is no reason to conclude that _A.atokensis_ and it's contemporaries of
the western interior could not have migrated to the east. In fact, I contend
that based on the presence of remains similar to those of Acrocanthosaurus,
Deinonychus, Astrodon (cf. "Pleurocoelus") and the recent discovery of basal
Neoceratopsian teeth in the Arundel, and it's slightly older age than
contemporaneous deposits of the WI, that may of the genera were here first or
at leased "passed" this way.

Sources,
Hallam,A., 1994. An outline of Phanerozoic Biogeography.Oxford. 246p .ISBN 0
19 854060 4

Smith, A.G., Smith, D. G., and Funnell, B. M., 1994. Atlas of Mesozoic and
Cenozoic Coastlines. 99p.  Cambridge. ISBN 0 521 45155 8

One of the Smiths has a web site with paleogeographic maps which can be
downloaded as well as a plethora of related material. In fact, I have the
Aptian map downloaded and saved as a my Windows wallpaper screen so every time
I boot up, I'm looking at the Aptian!




'm trying to determine possible faunal exchanges
>  between western and eastern N. America . 

As are a great many people....


I'm especially concerned with
>  whether or not A.atokensis could have inhabited the Southeastern United
>  States .

Me too!

 I understand that depositional characteristics east of the
>  Appalachians mitigate against finding much in the way of complete skeletons
>  , but this beast was large enough to at least leave some fragmentary
>  remains . Thanks in advance !
 

Well that's a bit hard to say. Part of the problem is due to the fact that
most of the older deposits either were not deposited in the first place, or
were removed at a later time. Here in Maryland we are lucky as the Arundel
Clay is only known withtin the state whereae the more sandy facies of the
Potomac Group are know to occur as fas south as Fredrickburg Va and as far
north as Raritan NJ and possibly Long Island.


Another must have...

Weishampel, D. B., and Young, L. 1996. Dinosaurs of the East Coast. 275 p.
Johns Hopkins Press. ISBN  0 8018 5216 1

Regards,

Thomas R. Lipka
Paleontological/Geological Studies