Re: reason for dropping Owen

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

On Fri, 7 Sep 2001, AM Yates wrote:

> > Padian and May were the first to provide a phylogenetic definition for
> > _Dinosauria_. It did not use any of Owen's original three dinosaurian
> > species. I believe the draft PhyloCode includes this as an example of an
> > improperly converted taxon, and suggests that it be based on Owen's three
> > species instead: Clade(_Hylaeosaurus armatus_ + _Iguanodon anglicus_ +
> > _Megalosaurus bucklandii_). (NOTE: The ICZN appointed _I. bernissartensis_
> > as the neotype of _Iguanodon_, so that may be a better anchor than the
> > dubious _I. anglicus_.)
>
> Hmmm. I'm not overly fond of this "use the original content for anchors"
> concept in PT. The concept of what various taxa  should or should not
> contain has evolved greatly since those taxa were first proposed. Take
> Archosauria for example. When Cope first proposed it he included a
> rag-tag bunch of reptiles (I can't remember the exact content off the
> top of my head but I'm sure plesiosaurs were in there). So is Gauthier's
> crown-group definition an improperly converted definition?

"...internal specifiers of converted clade names should be chosen from
among the set of taxa that were considered to form part of a taxon under
EITHER THE ORIGINAL OR TRADITIONAL IDEAS about the composition of that
taxon..." (emphasis mine)

Furthermore, it's just a recommendation, not a rule.

> My dislike of Padian's and May's definition of the dinosauria stems not
> from the fact that it doesn't use Owen's original taxa (after all one of
> them is a nomen dubium)

Hmm...

"Recommendation 11C. It follows from Recommendation 11B that phylogenetic
definitions of clade names should not use as specifiers species whose type
specimens are ambiguous (e.g., because they are lost or fragmentary)."

So using _I. bernissartensis_ instead of _I. anglicus_ would be entirely
warranted.

> but because they use birds. Although we all feel secure that birds
> evolved from within the Theropoda, a vocal minority of working
> palaeontologists do not share this view. Furthermore it is just better
> if birds are dinosaurs by discovery not by definition.

Extremely similar to what the draft PhyloCode says about this.

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