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Re: my working hypothesis for body size

At 08:43 PM 5/2/98 -0400, John Bois wrote:
>On Fri, 1 May 1998, Thomas R. Holtz, Jr. wrote:
>> Also, are global averages ecologically significant in the Late Cretaceous,
>> say, compared to the Late Triassic?  In Pangaean times, the world is
>> effectively one place, but due to continental drift and the rise of
>> epicontinental seaways, the landmasses of the early part of the Late
>> Cretaceous (in particular) were even more divided up than they are now.
>Is Carroll's (1997) claim, in _Patterns and processes in Vertebrate
>evolution_ wrong?  He says that Paleocene mammals radiated almost globally
>within a "few hundred thousand years".
Depends on the particular citation (a page number would be nice).

There is an adaptive radiation in the Paleocene, where many new forms appear
in diverse sizes and habitats over a geologically short period of time.
However, this is an adaptive radiation event (a sudden burst of adaptive
forms since the disappearance of the big dinos), not a migration event.

What is interesting about the Paleogene (more inclusive term than Paleocene)
radiation of mammals is that it occurs on all landmasses, *despite* the fact
that some were fairly isolated at the time.

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