No subject

Mike Crisp Mike.Crisp at ANU.EDU.AU
Fri Sep 1 09:23:41 CDT 1995

Richard Jensen says:

>I disagree with Murray Fletcher's view that any couplet having "not as
>above" is a poor couplet.  Some (many, most?) taxa are polythetic entities
>or are especially variable in individual characters - a simple way to
>isolate them in a key (rather than following them through all possible
>leads) is to specify the combination of characters that allows
>identification.  As long as no other taxon in the key has that precise
>combination of features, then the couplet works, and that's one key to a
>good key.

I agree.

I use 'not as above' frequently for taxa that have obvious diagnostic
characters but otherwise have nasty combinations of characters that don't
allow them to fall into either group of a major split I want to make
further down in the key.  If a taxon is very distinctive, either by virtue
of its autapomorphic characters or, as R.J. says, a unique combination,
then the meaning of 'not as above' is clear.

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