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Re: Campanian question
In a message dated 96-02-03 01:22:08 EST, email@example.com (Fred Bervoets)
>Who knows. Right now, I consider it most likely that the origin of the
>"Campanian explosion" is the accessibility and productivity of Judith River
>and Edmonton strata.
>I can't agree on this. (sorry)
And the accessibility and productivity of Asian strata, of course.
>Looking at the Campanian holotypes in Asia i see the same increase in
>diversity as in North America. There is an increase in diversity in the
>Asian Campanian of more than 250 %. My holotype count of the Campanian
>gives an almost equal count (Asia wins) in those two continents.
My point is that _whenever_ we find productive strata, of _whatever_
age--Jurassic, Cretaceous, etc., we find pretty much the same numbers of
dinosaur taxa in them. We happen to have a large number of Campanian to
Maastrichtian sites worldwide, so it looks as if there's a lot of Campanian
and Maastrichtian dinosaur diversity, and everyone starts to talk about
special circumstances in those epochs, etc., to account for this enhanced
dinosaur diversity. Whereas we really only have a diversity of sites rather
than taxa. Take a look at the list of Campanian and Maastrichtian sites
listed in _The Dinosauria_ and see how many there are.
You can't go by holotype counts, because they're highly dependent on the
number of sites at different levels in any region.