Message 2004-06-0036: Re: First International Phylogenetic Nomenclature Meeting

Wed, 16 Jun 2004 22:20:59 +0200

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Date: Wed, 16 Jun 2004 22:20:59 +0200
From: David Marjanovic <>
To: DML <>, PML <>
Subject: Re: First International Phylogenetic Nomenclature Meeting

----- Original Message ----- 
From: "Mickey Mortimer" <>
Sent: Wednesday, June 16, 2004 4:45 AM

> > > Diapsida Osborn 1903 = Apomorphy (1st reptile with
> > > Caiman crocodilus' two temporal arches/fenestra).
> >
> > That name _really_ cries for an apomorphy-based definition.
> > The apomorphy is very unambiguous (unlike "powered flight"
> > or "feathers"), and fossils around the base of Diapsida often
> > include skulls, so I don't see a serious problem here.
> M[]ller (2003) suggests the lower temporal arch of some saurians
> (rhynchocephalians, turtles, placodonts, choristoderes,
> rhynchosaurs+archosauriformes, trilophosaurs) is not homologous with that
> basal diapsids like Petrolacosaurus and Youngina.  If this is true, only
> Archosauriformes + Rhynchosauria node would be Diapsida according to
> Gauthier et al.'s definition, the lower arch in other clades being
> convergent.
> M[]ller, J., 2003, Early loss and multiple return of the lower temporal
> arcade in diapsid reptiles: Naturwissenschaften, v. 90, p. 473-476.

Well. The lower temporal arch of (Archosauriformes + Rhynchosauria) is not
homologous with those of the basalmost diapsids. The fenestrae are, though,
even though the lower one was open for a long part of Permian diapsid
history (and still is in over 1/3 of living diapsids) due to the absence of
the arch ventral to the fenestra.
        The lower temporal arch is also absent in the new arboreal clade and
*Claudiosaurus*, outside the crown-group.

> > > Rhynchocephalia Guenther 1867 = Apomorphy (1st lepidosaur with
> > > punctatus' premaxillary chisels).
> >
> > Probably similarly unambiguous. I just hope we can use *Sphenodontida*
> > suchlike for the stem. :-)
> I'm guessing they are derived from fused teeth, right?  Somewhere, a taxon
> existed with slightly fused teeth, resembling Sphenodon's morphology
> somewhat.  We'll just need to keep altering the definition if we keep it
> apomorphy-based.

Not if the "premaxillary chisels" are sufficiently described & illustrated.

> > > As does Sereno (gasp!)-
> > > Archosauria: Crown Clade (Crocodylus niloticus and Passer domesticus)
> >
> > Fine, fine. But using a nonavian dinosaur would have been even better
> > (Rec. 11A).
> Just what was Archosauria first designed to encompass?

In any case it was designed to be a reptilian subclass or superorder, and
thus to paraphyletically exclude birds. Following Rec. 11A Example 1, this
means that no internal specifier should be a bird.

> > Oh, they aren't even the problem. If he's right, then *Pterosauria*
> > not exist_. Why? Because *Pterosauromorpha* is defined as a part of
> > *Archosauria* -- and at least *Longisquama* is most likely not an
> > archosaur.
> So according to Phylocode, if you start a definition by saying "members of
> clade x that are...", and if the clade you define isn't a member of clade
> then the taxon is invalid?

This is not regulated. In this case, I applied logic. If pterosaurs are not
archosaurs, then there are no archosaurs that are closer to *Pterosauria*
than to *Dinosauria*, which means that *Pterosauromorpha* self-destructs.
And *Pterosauria* is defined as a part of *Pterosauromorpha*; if the latter
doesn't exist, the former can't exist either.


Feedback to <> is welcome!