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Re: transitional fossils

On Wed, 12 Jul 2000 ELurio@aol.com wrote:

> Quite a few. In fact there are so many reptile-mammal trasitional creatures 
> that the exact spot where the "transition" occors is quite arbitrary.

In phylogenetic taxonomy, there is no "reptile-mammal" transition, but
pre-mammalian lineage leading from basal Amniota to the first Mammalia.
Reptilia is a separate taxon.

Transitions are not from one taxon to another in phylogenetic taxonomy,
but within the same taxon and into new, more exclusive taxa.

The mammalian border is clearly defined in PT. Mammalia begins with the
most recent common ancestor of Monotremata, Marsupialia, and
Eutheria. (Note I said clearly defined, not clearly diagnosed ...)

T. Michael Keesey <tmk@dinosauricon.com> | AIM <Ric Blayze> | ICQ <77314901>
                 My Worlds <http://dinosauricon.com/keesey>
                 The Dinosauricon <http://dinosauricon.com>