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Re: More tyrant Q & A's



At 09:09 AM 12/9/98 -0500, Thomas R. Holtz, Jr. wrote:
>Bakker is famous for being a rather extreme "splitter" taxonomically: that
>is, in a given assemblage of fossils, he considers the actual in-species or
>in-genus variation to be very small, so that the assemblage should be broken
>up into many species.  Other people vary on how much variation they accept
>within a given species: some might consider all the specimens from one
>species, other people divide them in two, and so forth.
>
On ecological grounds, forms that co-occur in one time-place can really
only be distinct species if they differ sufficiently to be able to minimize
competition.  Given that Sue and Stan come from the same bed cannot be
different species, unless they are about 20% different in body length.
(And that really only applies if T. had deterministic growth - I suspect
that indeterminate growth ends up forcing even greater differences in
sympatric congeners).

>NOT a remote example, and very germane to the subject.  Some modern species
>DO vary widely in terms of their morphology.  This is a problem in taxonomy
>(modern and paleo-): where do we draw species boundaries.

Quite.  And living species that are most similar to one another live in
distinct geographic areas.  This helps, if one uses this fact in analyzing
the fossil record.

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May the peace of God be with you.         sarima@ix.netcom.com