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Date: Tue, 15 Jun 2004 19:45:20 -0700
From: Mickey Mortimer <Mickey_Mortimer111@msn.com>
To: dinosaur@usc.edu
Cc: phylocode@ouvaxa.cats.ohiou.edu
Subject: Re: First International Phylogenetic Nomenclature Meeting
David Marjanovic wrote- > > 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. 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 convergent. 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 apomorphy-based. > > Crurotarsi Sereno and Arcucci 1990 = Apomorphy (1st archosaur with Caiman > > 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 longipes > + > > 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 (Rec. > 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 S. > > 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 to > > 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, or > > 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 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 x, then the taxon is invalid? Mickey Mortimer Undergraduate, Earth and Space Sciences University of Washington The Theropod Database - http://students.washington.edu/eoraptor/Home.html