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More instability? (*Eudibamus*)




Diagnosis is one thing, but cladistic definitions, especially the one being discussed, can be very destabilizing. Although I must admit, I am glad to see Mesosauriformes back in the Anapsida (rather than the cladistic orphan it was for a while).
The crown clade definition of Reptilia (unilaterally imposed by cladists who obviously didn't have stability in mind) looks like it may well come back to haunt them. If Testudiniformes are not Anapsids (and it is increasing looking as if that is the case), the crown clade Reptilia will be even more greatly restricted, and in all probability will become a virtual synonym of Sauria.
Good luck trying to explain these new changes to the public or confused biology students. Don't worry everybody, the cladists will assure us that such a change will not occur again---they've got it right this time, and stability is just around the corner. Yeah right!!??
------Eclectically yours, Ken Kinman
P.S. Sorry David, but the cladistic "Reptilia" will probably soon be morphing into something new, and the eclectic Reptilia never went away. The only difference is that the content of the traditional eclectic Reptilia has remained the same, while the only thing constant about the content of cladistic Reptilia is its ability to keep changing.
TRANSFORMATION of taxonomy from one extreme to the other: eclectic authoritarianism has slowly given way to cladistic authoritarianism, and I for one am really tired of the pendulum swinging from one extreme to another. Semi-paraphyletic (i.e., semi-holophyletic) taxa are the only answer to this dilemma of perpetual instability.
---K.E.K.
********************************************************
From: "Jaime A. Headden" <qilongia@yahoo.com>
Reply-To: qilongia@yahoo.com
To: dinosaur@usc.edu
Subject: Is *Eudibamus* a Reptile?
Date: Sun, 17 Dec 2000 07:33:24 -0800 (PST)

David Marjanovic wrote:

<Heh, heh. If we accept the phylogeny in the Science paper on
Eudibamus, then Mesosauridae belongs into Parareptilia/Anapsida, and
Reptilia has the same content as Sauropsida, so it can be
(yabbadabbadoo) ignored in favor of the latter, and the debate whether
we should call a bird and/or another dinosaur a reptile can be ended.
Like Huxley said in the 19th century, it is a sauropsid.>

  It may be both: Sauropsida is a stem-clade, defined as anything
closer to one form than another, whereas Reptilia is a crown-group
node-clade, defined as the most recent common ancestor of a living set
of organisms, including its fossil descendants. In this case,
Sauropsida includes Reptilia, but is still valid in either case. The
content may be the same, but a new fossil could change this, and
*Eudibamus*' only claim to fame will be its hips....

  Clade names are not just content related, which they were prior to
distinguishing the nature of their _diagnosis_ and their _definition_.

  Good Morning, Neverland!

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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