Re: Kileskus and Proceratosauridae

["T. Michael Keesey" <keesey@gmail.com>]

On Wed, Mar 31, 2010 at 4:18 AM, Jaime Headden <qi_leong@hotmail.com> wrote:
>
> Â Unfortunately, the idea that a "clade" is the general product of a 
> cladistic analysis, or is any grouping to be found on a tree, is common at 
> least in the lay media. I do not have a specific citation. I do not aver 
> that this is an authentic use of the term, but that it has been used as such.Â
>  This is, again, replicated in the lay media, who did not themselves make 
> this out of whole cloth. As far back as at beginning of the use of 
> cladistics in the discussion on this very mailing list, at least, the term 
> "clade" was being used as a form of "uppity" expression equivalent to 
> "group."Â A "paraphyletic clade" and a "paraphyletic group" and a 
> "paraphyletic grade" were essentially the same things, depending on who was 
> using them.
>
> Â As a special note, even our own Mike Keesey has used the term, which I've 
> dug up here: http://dml.cmnh.org/2001Dec/msg00054.html

No, that's me quoting Rob Schenck. "Paraphyletic clade" is an oxymoron
-- there is no such thing, any more than there are square planets or
negatively-charged protons.

> Â I've also become somewhat confused, as I was aware that the recent shift 
> for absolute definitive understanding to the term "clade" is abruptly recent; 
> I am not familiar with a concrete definition for "clade" in many of at 
> introductory texts on the matter that I've read, although I've not read some 
> of the more recent ones

"Clade" has always referred to "an ancestor and all of its descendants".

In my 2007 paper <http://dx.doi.org/10.1111/j.1463-6409.2007.00302.x>,
I discussed the question of what comprises an "ancestor". To account
for cases where organisms have multiple parents, I found it necessary
to coin a new term, "cladogenetic set", for a taxon having these
properties:

1. No member is ancestral to any other member.
2. All members share at least one common successor.

"Successor" = "descendant or self", so all singleton taxa would be
cladogenetic sets. Another example of a cladogenetic set would be two
parents who have one or more children together. Larger sets may be
cladogenetic as well.

Subsequently I shortened the term to "cladogen" and changed "member"
to "subunit", so that it would be applicable at various levels of
resolution (species, population, individual, etc.) This is in a
specification that is still being worked on, here:
http://namesonnodes.org/ns/math/2009/

So, to arrive at the point, more specifically, a clade would be the
union of a cladogen and all successors of all subunits of that
cladogen: http://namesonnodes.org/ns/math/2009/index.html#section-Clades

> Â What was the original useage of the term "clade?" I would follow that up 
> with who defined the term, and where it was defined? These things would be 
> interesting from an historical point.

Julian Huxley coined the term in 1957. I don't have access, but the
paper is here if anyone wants to check:
http://dx.doi.org/10.1038/180454a0

-- 
T. Michael Keesey
Technical Consultant and Developer, Internet Technologies
Glendale, California
http://tmkeesey.net/