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Re: Theropod "migrations"



At 04:19 PM 4/26/99 +0200, Berislav Krzic wrote:

>So the different rate of evolution change of
>carnivorous dinosaurs and herbivorous ones in a new environment during a
>certain (not very long) period led to the impression that mainly the
>carnivorous dinosaurs were migrating. Fact is, they couldn't have migrated
>very far without their food supply: they had to follow their prey - the
>herbivores must have crossed the bridge first.

While your hypothesis of evolutionary rates may be true, in fact the food
supply for carnivorous dinosaurs was already there: the local herbivorous
fauna.  So it is not necessary for them to follow the herbivores, since meat
is already present.  (That is not to say that they *didn't* follow: however,
our current resolution for the hypothesized earliest Late K immigration
event isn't fine enough to tease out that level of detail).

That is the point of the comment "meat is meat": for most carnivores, it
doesn't matter if it feeds on the meat from a local animal or the meat of
animal from another part of the world.

Many herbivores, however, have much more particular food requirements (only
certain plant species), and thus cannot migrate (or immigrate) into new
regions if their food stuff is not present.

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