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Re: tooth counts in systematics
chris brochu wrote:
> You've got some great points here, but they actually focus on two
> independent issues.
Yeah, that doesn't surprize me at all...
> One of them is intraspecific variation. Norell's talk at the Ostrom
> Symposium gently chastized all other previous theropod systematic
> studies for ignoring (or miscoding) interspecific variation, e.g. by
> coding a large multispecific group with a single character state, and I
> think we'll see more rigorous approaches to this in the future.
> Intraspecific variation is a different matter, and as we've discussed,
> there are ways of handling it - provided it's made explicit in the first
I hope Mark doesn't take offense at this, but I thought that that
was the best talk I have heard him give. He said a lot of things that I
had been waiting to hear a systematist say. Honestly though, I didn't
expect him to be the source of it. I was very pleasently surprized.
> > Your other concern involves explicit, unambiguous character state
> definitions, which can be viewed as an independent problem. Part of the
> problem, I think, is that most theropod phylogenies after Gauthier 1986
> focused on discussions of the tree, with minimal character discussion.
> (And you theropod people are not alone - I can think of a couple of croc
> papers by a certain Field Museum employee that are just as guilty.)
> It's possible, or even probable, that the author of such characters has
> clear states in mind, but a two-sentence descriptor makes it difficult
> for others to use the matrix. Adding lengthy character discussions
> makes papers VERY long and hence difficult to publish.
> I learned my lesson last year, after the Gavialis and Leidyosuchus
> papers came out. A couple of people tried to code new taxa on my
> matrix, and in some cases they were clearly misunderstanding the
> characters I used. And this was my fault, not theirs - I should have
> published figures along with each character, specifying what I meant.
> (This situation is partially rectified in a forthcoming alligatoroid
> phylogeny, which should be out this summer. The other portions of the
> tree will have to await completion of Sue - and any characters I use in
> the Sue analysis will be thoroughly figured.)
> A possible third issue, which is also independent, is hinted at in what
> you wrote - the problem of multiple primitive states. ALL character
> states in a character should be explicitly defined. "Orbit keyhole
> shaped versus not keyhole shaped" leaves open the possibility that one
> of your states could actually be many states - "not keyhole shaped"
> could mean oval, circular, or horizontally slitlike. (For what it's
> worth, it would be better to define this character with respect to the
> presence or absence of an anterior process on the postorbital - but
> that's another discussion.) This is variation, but of a very different
> The linkage between your points comes with the explicit discussion of
> the characters. Any character discussion should include intraspecific
> variation, if any; its limits, nature, and any reasons for not coding
> it; and so on.
Not much that I can say about all of this except that I (?predictably)
agree completely. Character description/discussion has been my principal
anti-cladism bitch for a while now (ask Holtz about long days in the
Lance of characters, beef jerky, and Simpson's quotes...). There are
several sorts of variation here that need to be accounted for in
analyses, but I understand quite well the very real editorial problems
associated with character matrices. Maybe places like JVP et al. are
just not the vehicles to present these sorts of works and as such the MCZ
or YPM bulletins need to be revisited more. I don't know. I will be
pigheaded though and maintain that these issues of character
desciption/discussion and handling of intra/intertaxonomic variation need
to be addressed if we are going to get theropod systematics beyond the
"flavor of the month" stage that it seems to be in right now.
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