Message 2004-06-0020: Re: First International Phylogenetic Nomenclature Meeting

Tue, 15 Jun 2004 19:45:20 -0700

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Date: Tue, 15 Jun 2004 19:45:20 -0700
From: Mickey Mortimer <>
Subject: Re: First International Phylogenetic Nomenclature Meeting

David Marjanovic wrote-

> > Diapsida Osborn 1903 = Apomorphy (1st reptile with Caiman crocodilus'
> > temporal arches/fenestra).
> That name _really_ cries for an apomorphy-based definition. The apomorphy
> very unambiguous (unlike "powered flight" or "feathers"), and fossils
> the base of Diapsida often include skulls, so I don't see a serious
> here.

Muller (2003) suggests the lower temporal arch of some saurians
(rhynchocephalians, turtles, placodonts, choristoderes,
rhynchosaurs+archosauriformes, trilophosaurs) is not homologous with that of
basal diapsids like Petrolacosaurus and Youngina.  If this is true, only the
Archosauriformes + Rhynchosauria node would be Diapsida according to
Gauthier et al.'s definition, the lower arch in other clades being
Muller, J., 2003, Early loss and multiple return of the lower temporal
arcade in diapsid reptiles: Naturwissenschaften, v. 90, p. 473-476.

> > Rhynchocephalia Guenther 1867 = Apomorphy (1st lepidosaur with Sphenodon
> > punctatus' premaxillary chisels).
> Probably similarly unambiguous. I just hope we can use *Sphenodontida* or
> 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

> > Crurotarsi Sereno and Arcucci 1990 = Apomorphy (1st archosaur with
> > crocodilus' fully rotary, hemicylindrical, fibulocalcaneal crurotarsal
> articulation).
> Should better retain its original stem-based definition. Ah, this will be
> replaced with *Pancrocodylia*...

Another instance of a fine stem-based clade being overthrown by a Pan-stem.
Grr...  "Is this basal condition _really_ hemicylindrical?" "Is it _fully_
rotary?  I mean, surely Caiman can't rotate it's tarsal joint completely
around, 360 degrees."

> > Sauria MacCartney 1802 = Crown (Sphenodon punctatus +
> > Draco volans + Caiman crocodilus + Vultur gryphus).
> Why *Draco*?
> I've never seen Sauria being used precladistically in anywhere near this
> sense. It's always used as a synonym of the rarer name Lacertilia -- the
> paraphyletic lizards without snakes and sometimes amphisbaenians.

I assume Draco is the first genus listed by Linnaeus.

> > Finally, Gauthier et al. add Compsognathus to the definition of
> Archosauria-
> > Archosauria Cope 1869 = Crown (Caiman crocodilus + Compsognathus
> +
> > Vultur gryphus).
> > Just why are dinosaurs constrained as archosaurs?
> Perhaps just to be really certain, so that the BANDits can't complain?

Why do they care if dinosaurs are archosaurs?  They demand birds,
Longisquama and drepanosaurs be archosaurs, but I don't see how
non-archosaurian dinosaurs would adversely affect them.

> > As does Sereno (gasp!)-
> > Archosauria: Crown Clade (Crocodylus niloticus and Passer domesticus)
> Fine, fine. But using a nonavian dinosaur would have been even better
> 11A).

Just what was Archosauria first designed to encompass?

> > Neornithes finally gets an official definition, from Sereno-
> > Neornithes: Crown Clade (Passer domesticus not Crocodylus niloticus)
> =8-)

Oh, it seems Hope (2002) already defined it-
"Neornithes applies here to the monophyletic group indicated by extant
birds, their most recent common ancestor, and all its descendants." (p. 341)

> > And isn't the type species of Stegosaurus S. armatus?  Why does he use
> > stenops?  Wagner knows to use S. armatus.
> *S. armatus* is the type. *S. stenops* is better known... or at least much
> more famous. Has more beautiful plates.

S. armatus is still definitely a stegosaur, there's no reason to use a more
complete taxon.

> > And Sereno's always right, of course, so let's define Heterodontosaurus
> > be an ornithopod! ;-)
> > Ornithopoda: Clade (Heterodontosaurus tucki and Parasaurolophus walkeri)
> > I'll be using Wagner's definition-
> > Ornithopoda: Clade (I. bernissartensis not A. magniventris, S. armatus,
> > C. montanus)
> I agree. But only one of these two definitions can survive!

I see neornithischian heterodontosaurids as being more likely, so if
Sereno's becomes official, Ornithopoda would be invalid.

> Oh, they aren't even the problem. If he's right, then *Pterosauria* _does
> not exist_. Why? Because *Pterosauromorpha* is defined as a part of
> *Archosauria* -- and at least *Longisquama* is most likely not an

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 x,
then the taxon is invalid?

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database -


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