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Re: Revised Ornithischian Classification

David,
No, I don't plan to write a paper. As I said in the recent disclaimer, I am a classificationist, and simply attempt to act as a catalyst of sorts, weaving conflicting cladograms, interpretations, and opinions, into a classification that I hope gradually narrows down possibilities, encourages more discussion, and perhaps along the way persuade a few more people that carefully chosen paraphyletic groups can serve a valuable purpose (whether they are recognized temporarily or permanently).
I do agree with Mickey that a more complete cladistic analysis of the these various ornithischians (especially hypsilophyodontids) is badly needed, and Pete and various others are working in this area. I personally would love to see Mickey and Jaime get together and do such an analysis and publish their results. The more analyses there are, the better, since independent analyses can be used to correct each other and lead to even better analyses. And also resolve some differences, such as whether Tenontosaurus dossi makes that genus holophyletic or paraphyletic (Mickey pretty persuasively argues that it is the latter).
In any case, I believe the scaled-down version of a paraphyletic Hypsilophodontidae that I favor (with only one exgroup, namely the dryomorpha clade) will be useful. The older and broader version of this family (including genera like Agilisaurus and Thescelosaurus) was too broad and too paraphyletic (also giving rise to heterodontosaurs and marginocephalians).
If paraphyly is overused, not handled carefully, and not explicitly labelled, cladists should be critical of such practices. But on the other hand, reducing formal paraphyly to zero (automatic rejection of all such taxa) is not only impractical, but too simplistic and philosophically untenable in reflecting the complexities of evolutionary history.
----Ken Kinman
****************************************** 
From: "David Marjanovic" <david.marjanovic@gmx.at>
Reply-To: david.marjanovic@gmx.at
To: "The Dinosaur Mailing List" <dinosaur@usc.edu>
Subject: Re: Revised Ornithischian Classification
Date: Wed, 22 Aug 2001 00:22:36 +0200

> If I thought hypsilophodonts could be divided into two clades (as you
> did), I would see no real need for a paraphyletic family. But the closer
I
> look, I see more and more small clades splitting off sequentially (far
more
> than 2).

While I have no opinion on this, could you tell us some evidence for this,
or are you planning to write a paper on it?

> Therefore, I believe it is strict cladification that is the bad
> idea in this case, because it would require perhaps 10 small families or
> more (there could be one or two Australian clades splitting off separately
> that would require more families).

...that's why I dislike ranks :-)

> Since most dinosaurologists continue to
> assign these forms to a Family Hypsilophodontidae,

Most dinosaurologists don't use families anymore, and Hypsilophodontidae in
such a broad sense at least has gone completely out of use in the last few
years.

BTW, it's *Leaellynasaura*, with eae, after Lea Ellyn Rich AFAIK.



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