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Re: eggshells, therizinosaurs & tyrannosaurs




Jeffrey,
I agree that this generally causes no practical difficulties at lower taxonomic levels, but the higher and more inclusive the taxa, the more problems it causes.
Dave Peters' "Ornithodira" is a much broader taxon than Ornithodira sensu stricto (ooops, I'd better say sensu Gauthier or Sereno). So if Dave Peters is correct (that pterosaurs are prolacertiforms), Ornithodira needs to be redefined or it will be much more inclusive. Either way, it is destabilizing.
But such problems will pale into insignificance compared to Woesian misconceptions and misnaming. Calling a major group of organisms "Archaea" or even "Archaebacteria", instead of Metabacteria, is having an impact on bacteriological systematics so sweeping that most biologists are totally unaware that it is happening.
This is not to say that some choices are not mostly aesthetic. The terms Animalia and Metazoa are now used interchangably, and this causes no big problems---in this case, I agree with you (so what?).
Each and every case is different and needs to be evaluated separately. In some cases, "so what" is a perfectly appropriate response, but in others, the consequences can be very damaging in both the short tern and the long term.
-------Ken Kinman
******************************************************
From: "Jeffrey Martz" <jeffmartz@earthlink.net>
To: <tmk@dinosauricon.com>, "Ken Kinman" <kinman@hotmail.com>
CC: <dinosaur@usc.edu>
Subject: Re: eggshells, therizinosaurs & tyrannosaurs
Date: Wed, 19 Jul 2000 21:35:35 -0000


> I think this has already happened with Ornithosuchia, which >according to
many phylogenies no longer includes Ornithosuchidae >(type genus
Ornithosuchus).


>Excellent example. (Wasn't that one also Sereno's?)

No, Ornthosuchia is a stem-based clade (all archosaurs closer to birds
then to crocodilians) established by Gauthier (1986; his Saurischian monophyly paper, which I unfortunately can't find right now). Gauthier also
named "Ornithodira" as a node based clade within Ornithosuchia, which
included dinosaurs, pterosaurs, and Lagosuchus, but excluded the
Ornithosuchidae and Euparkeria (these were in Ornithosuchia in Gauthier's
analysis). However, since these latter two taxa fall into Pseudosuchia and
in basal Archosauriformes respectively in most later cladistic analyses, the
membership of Ornithodira is now pretty much synonymous with Ornithosuchia
(assuming the pterosaurs belong and nothing is found to be an Ornithosuchian
outside of Ornithodira). I'm not sure what taking pterosaurs away from the
Ornithosuchia would do to Ornithodira. Since both groups were defined in
the same paper, I'm not sure if Ornithodira might not be an equally valid
name (if the pterosaurs stay).
In any case, the Ornithosuchia-Ornithosuchidae "problem" is a purely
asthetic one. The idea of a higher level taxon that is named for
Orntihosuchus and its kin but doesn't include them bugs people, but doesn't
really cause practical difficulty. I know the difference between
Ornithosuchia and Ornithosuchidae. You know the difference between
Ornithosuchia and Ornithosuchidae. Where is the problem?
Same thing with Pseudosuchia and 'Crocodylotarsi'; so what if
crocodiles are included in a clade that translates into "false crocodile"?
If we want to get philosophical, most of the pseudosuchians ARE "false
crocodiles", things that look sort of croc like but aren't.
Aesthetic problems with names is a bogus reason to create new ones that
creates just forces authors to have to write more in the introduction of
thier phylogenetic analyses. The amount of confusion it causes is greater
then the confusion it supposedly fixes by introducing
"more appropriate"
names.

LN Jeff

He who stops at being better stops being good.
-Oliver Cromwell

Fear not those who argue but those who dodge.
-Marie von Ebner Eschenbach

Jeffrey W. Martz
3002 4th St. # C26
Lubbock, TX
79415
http://www.homestead.com/illustrations/Illustration
(806) 747-7910


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