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RE: ICZN & PhyloCode (was RE Stegosaur volume of Swiss Journal of Geosciences
This question comes up enough on this list that it seems interesting it still
comes up. Hasn't the general conclusion of "diagnostic" being subjective been
regarded as essentially "unsolvable" so far?
Anthony asks (perhaps rhetorically) "How many diagnostic characters can you
glean from teeth?"
If you were a mammologist, one may very well be enough, as Anthony himself
affirms. This depends, of course, on how far you are willing to bend the term
diagnostic, and to what _degree_ of diagnostic you value this tooth's one
feature. In mammal dental series, it is often the context of a series of
changes along the row that counts, not any one tooth, and applying this
criterion to reptile teeth, which are often very close in morphology to one
another along the tooth row, or vary largely only in proportions of the crown,
but through no superficial characters.
When it comes to some theropod teeth, differentiating uppers and lowers can be
tricky, although some workers (it is said of Currie, for example) have become
adept at identifying the position at a glance. Tyrannosauroid teeth are good
models for variation, both proportionate "heterodonty" and superficial
morphologic "heterodonty." (I cover this specific issue here:
Tyrannosaurs are, somewhat, too easy. Try identifying a hadrosaur corwn to
position. A lot harder. No study (to date published) has addressed variation
along dental batteries in ornithischians, and the few that have have dealt
largely with ontogeny or replacement, and not variation: A ceratopsian crown is
just that, a crown, and it's neither an upper or a lower, nor a mesial or a
distal, and variation is measured by wear. And ontogeny is barely a factor.
So when next we deal with this question, I suggest a little more focus on what
"diagnostic" actually means, and how you use it: it might free up some
discussion time to something more productive on the topic, like assessing
variation in regards to "diagnostic" material, and thus allowing us to assess
whether taxa which are "diagnostic" are useful in any way.
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Tue, 21 Sep 2010 02:05:42 +0000
> From: email@example.com
> To: firstname.lastname@example.org; email@example.com
> Subject: RE: ICZN & PhyloCode (was RE Stegosaur volume of Swiss Journal of
> > Date: Mon, 20 Sep 2010 18:51:03 -0700
> > From: firstname.lastname@example.org
> > To: email@example.com
> > CC: firstname.lastname@example.org
> > Subject: re: ICZN & PhyloCode (was RE Stegosaur volume of Swiss Journal of
> > Geosciences
> > On Mon, 20/9/10, Anthony Docimo wrote:
> > > I could understand why a person might consider a nomen dubium to be crap.
> > Nomina dubia are always crap. But crappy specimens are not always
> > necessarily nomina dubia. You need only one diagnostic character to be
> > gleaned from a specimen in order for it to qualify a valid taxon.
> > > >_Tyrannosaurus_ is infinitely better than _Deinodon_,
> > >
> > > why is that?
> > Because _Deinodon_ is known only from teeth.
> how many diagnostic characters can you glean from teeth?
> as you just said, you need only one.
> > > > Y'know, I would use the Deinodontoidea example as a *reductio ad
> > > > absurdum* to show why blindly applying ICZN rules is so
> > > > counterproductive. There is just no way that Deinodontidae should be
> > > > used in place of Tyrannosauridae,
> > >
> > > why not?
> > Tyrannosauridae has over a century of usage, and is based on none other
> > than _T. rex_.
> > Go ahead. Try using Deinodontidae instead of Tyrannosauridae. See how many
> > people follow your lead. ;-)
> you know where I saw _Deinodon_ being used? in a book about Barnum.
> > > the fact that there are exceptions, automatically means "something is
> > > rotten"?
> > The fact is that family-level nomenclature as dictated by the ICZN often
> > serves dinosaur taxonomy exceedingly poorly.
> being upset that the ICZN doesn't always make a perfect fit with dinosaurs,
> is like being upset that Roman numerals don't handle complex algebraic
> fractions well.
> (someone once told me Roman numerals had that problem)
> > > so...."it is bad to fix problems" AND "it is bad to leave problems
> > > alone". please make up your mind.
> > My point was that because of the clunky nature of certain ICZN rules, that
> > these rules are often circumvented or ignored. That's why Tyrannosauridae
> > is used instead of Deinodontidae, despite (as Mickey notes) the latter
> > having priority. Strict application of priority would see Tyrannosauridae
> > trumped by Deinodontidae. Now, speaking for myself, I think this is a bad
> > thing, because, well, I've kinda gotten used to Tyrannosauridae.
> and people have gotten used to Ceratopsidae.
> > Plus, my sympathies go to _Tyrann
> > rus_ over _Deinodon_ over who should get the honor of having a family named
> > after it.
> why sympathies?
> > > wait, you were just calling for the rules being hard-and-fast and
> > > applied equally everywhere.
> > No, I certainly wasn't.
> you want us to use Tyrannosaurus/Tyrannosauridae instead of
> Deinodon/Deinodontidae _because of how it feels_...yet you want us to use a
> different yardstick for Ceratops.
> > > by that logic, please stop your protests about Ceratops. experts in the
> > > field have already made their choice.
> > Actually, they haven't. If said experts had settled on _Ceratops_ being an
> > appropriate genus to name a clade after, they would include _Ceratops_ in
> > the definition of Ceratopsidae. But they don't; not ever. _Ceratops_ (the
> > name-giving genus) is conspicuously absent from ANY published definition of
> > Ceratopsidae. That's a vote of no confidence in _Ceratops_. Therefore,
> > Ceratopsidae cannot stand. Either include _Ceratops_ in the definition of
> > Ceratopsidae, or forgo _Ceratops_ as a name-giving taxon. You can't have it
> > both ways.
> > It's also pertinent that those same experts have yet to decide whether the
> > sister taxon to Centrosaurinae should be called Ceratopsinae or
> > Chasmosaurinae. Both Ceratopsinae or Chasmosaurinae have been used, and
> > still are. Again, _Ceratops_ is the root of the trouble, and is causing
> > instability at the 'subfamily' level.
> if I ever get a TARDIS, I'm going back and napalming the early ceratopsians
> and protoceratopsians until no bones remain. problem solved.