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Re: Daspletosaurus: Part 2



At 02:07 AM 2/4/98 EST, Dinogeorge wrote:

>The extreme unlikelihood of this scenario is what made me decide that the
>Asian tyrannosaurids--like protoceratopids and certain other dino
>groups--underwent their own evolution independently of the North American
>forms. With the sea level 100+ meters higher than it is today, and major
>epicontinental flooding throughout the Campanian and Maastrichtian, there is
>no way any Asian forms could have gotten over to western North America across
>the Bering region or any other way during those epochs.

Although global sea levels were higher during the later part of the Late
Cretaceous, it is dangerous to extrapolate this to all regions.  Regional
sea levels can vary quite a bit due to tectonic activity.  As the Alaskan
region is one of THE most confusing spots tectonically during the Cretaceous
(being a patchwork of smaller platelets), and Siberia very poorly known, it
is invalid to say that there s no way any Asian form could cross over or
vice versa.

In fact, until the geology is worked out, morphological and phylogenetic
similarity of Asian and western North American fauna and flora might be used
to indicate the possibility of exchange.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661