Re: definition of diapsida via "Feduccia's delusion"

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Sat, 1 Dec 2001, Rob Schenck wrote:

> so a definition of a clade cant change, but that clade can be found to
> be invalid, unnatural, paraphyletic etc, but regardless, it will
> allways be defined as such.

The ways in which most clades are defined does not allow them to be
anything but monophyletic.

1: "The most recent common ancestor of A and B [and C ...], plus all of
its descendants."
2: "The least recent ancestor of A which is not also an ancestor of B [and
C ...], plus all of its descendants."

Well, there is one way these could be invalidated -- synonymy among
the specifiers.

> An paraphyletic clade

Oxymoron. A clade is a monophyletic group.

>  As for the super rank, then cladistics has no rank?  but what about
> genus?  how does the genus level fit in?

Genera have been retained as a matter of convenience, but the ultimate
goal would be to have only two types of taxa: clades and species. There
are many proposals for how to deal with genera -- we'll see which one wins
out.

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