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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