"crown taxa"

[Una Smith]

On Tue, Apr 23, 2002 at 07:41:20AM +0200, B.J.Tindall wrote:
>I was looking for a definition of "crown taxa" since I was not sure whether
>I understood the term correctly and couldn't find anything conclusive. My
>initial impression was that "crown taxa" were those organisms living today,
>but I have seen the term used in such a way that it would mean that crown
>taxa are vertebrates and higher plants etc., whereas protists would not be
>considered to be crown taxa. Could anyone provide more information?

Crown taxa are those members of a clade that share (recognizable)
synapomorphies.  Stem taxa are members of the (larger) clade that
instead have plesiomorphies.  Usually, crown taxa are numerous,
stem taxa are few (this is a product of the concept of crown and
stem, not a definition thereof).

Hope this helps,

        Una Smith

Los Alamos National Laboratory, MS K-710, Los Alamos, NM  87545