Ceratopsian Systematics [was: Avaceratops and Ceratops (was Re: THE NEW ISH OF JVP)]

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

Timothy Williams wrote (please don't take offense at the rant here, Tim!):
>Could _Avaceratops_ 
>be a juvenile _Ceratops_?  (For those who believe that _Ceratops_ is a 
>defunct genus, read on...)
        Only if _Ceratops_ were valid. What the specimen really shows,
according to Tom Lehman, all-too-rarely acknowledged ceratopsian expert, is
that _Ceratops_ is not only generically indeterminate, but indeterminate at
the "family" level as well.

>(2) Even if this new skull does not belong to _Avaceratops_ it belongs to a 
>closely related genus, probably a basal ceratopsid like _Avaceratops_.  
        Assuming _Avaceratops_ is a "basal" ceratopsid at all, which is at
this point supported by a *single* study. Others are less certain that it is
even a valid genus. One point upon which I am very concerned is the coding
of characters from a juvenile specimen. While I think there may be some
value to the practice, one must bear in mind that:
        a) ontogeny does sometimes *almost* recapitulate phylogeny, and it
is possible that juvenile will appear more "basal" relative to adult sister
taxa.
        b) ontogeny doe not *completely* recapitulate phylogeny, which may
result in unusual charachter combinations which never existed in adult taxa.
        For these two reasons, I am already skeptical of this result,
although I have to admit, I have only had access to a summary of the article
(since the press seems to be pulling its usual goof-fest with my subscription).

>(3) In another paper in the same issue of JVP, Sereno calls the sister-group 
>to the Centrosaurinae Ceratopsinae rather than Chasmosaurinae.
        He has done this in the past... in fact, in his Science article he
goofed and had Ceratopsinae+chasmosaurinae.

>Now, Sereno 
>is a stickler for nomenclatural correctness
        OH WHATEVER! Good lord, has the world gone blind?!?!?!?! If the
above statement is true, I will sit naked in the middle of the AMNH "whale
hall" with a plaque on my chest that reads "I am Paul Sereno's monkey-boy."
Sereno is no stickler for anything, and neither are most paleontologists.
The *only* true stickler I know is George Olshevsky, who is truer to the
letter-and-law of the ICZN Code than *any* tenured professor in the world
AFAIK. Dr. Sereno calls upon the letter of the law if and only if it suits
his purposes. In this case, he wished to get rid of Chasmosaurinae, and he
found a way to do it. Those rules are ENTIRELY meaningless in phylogenetic
taxonomy. He used what authority he could find to get the outcome he wanted.
        This is just like when he got rid of several African spinosaur taxa
so he could justify naming _Suchomimus_. WAKE UP PEOPLE! This is how some
people work. Heck, I'll admit that I will use whatever rules I think are
valid to correct what I percieve to be errors in taxonomy. I even plan to
appeal to the "Padian, Hutchinson and Holtz" precedant of simply ignoring
priority for everyone's best interest. The difference is, I won't hide
behind the rules, I'll say just what I mean to do: I don't think
_Heterodontosaurus_ is a useable anchor for Ornithopoda, I think
"Neornithischia" stinks, and Cerapoda is a meaningful, useful taxon, I can't
believe how many nodes Sereno names, and I think fewer names should be used.
        Anyway, let's exercise a little more critical thinking and a little
less hero-worship around here. You want good taxonomy, go read Padian,
Hutchinson and Holtz. You want glitz, flash, and a zealous, aggressive,
non-consentual approach to taxonomy, keep admiring Sereno.
        End of rant. Apologies if I have misrepresented Tim in any way.
Honest Tim, I think you're aces, I'm just a little worn down by this sort of
thing.

>(e.g. he abandoned the name 
>Titanosauridae in favor of Saltasauridae because the _Titanosaurus_ type 
>material is probably non-diagnostic).
        But it is titanosaur, something you can't say about _Ceratops_
(vis-a-vis Chasmosaurinae). Again, he just wanted to name it. As a matter of
fact, according to a buddy of mine in the titanosaur business, _Saltasaurus_
was a TERRIBLE choice, being as it is an especially bizzarre individual. But
Sereno wanted a "well nested" taxon. Of course, he neglects to account for
the morpholgical version of "long-branch attraction", whereby,either due to
the taxonomic scope of you study, or simply lack of information, some taxa
end up well "nested" in your ingroup with a lot of reversals rather than at
the more "basal" position they should hold (see _Mononykus_, and, fide
George, therizinosaurs). Also, "nested" is an entirely arbitrary situation,
highly dependant on selection of ingroup taxa (either by the worker or the
fossil record), and by how one chooses to arrange one's tree.

>Sereno must believe that _Ceratops_ 
>must be a good genus to name a higher-level taxon after it
        Actually, in the notes to his Neues Jahrbuch paper he states
otherwise: he claims that it is not necesssarily diagnostic, but is
"definitely Chasmosaurine." See what I mean? Any excuse...

>(especially since 
>almost everyone else, George Olshevsky excepted, calls this clade the 
>Chasmosaurinae).
        Since Lehman solidified the the arrangement in his paper in Dinosaur
Systematics in 1990.

>At any rate, there's no good evidence that _Ceratops_ is a 
>chasmosaurine (see (1) and (2)).
        Hear hear!

>Sereno, P C.  1999.  A rationale for dinosaurian taxonomy.  JVP 
>19(4):788-790.
        FYI: Sereno's "rationale" is irrational, and violates several
principles of Phylogenetic Taxonomy (e.g. obligatory taxa) and his taxonomy
is poorly arranged and contrary to the guidlines suggested by DeQuiroz and
Gauthier (type taxa, elimination of excessive or redundant taxa). I also
disaggree with many of his taxon definitions, but more on this in a few years...

And "Timothy Williams wrote again:
>And maybe _Triceratops_ too, another solid-frilled ceratopsid.  It's looking 
>more and more possible that _Triceratops_' absence of parietal fenestrae may 
>not be due to secondarily loss after all.
        Yeah, whatever! The structure of its narial area is clearly
chasmosaurine (which is the more derived of the two morphologies), it shares
a number of synapomorphies with more "derived" chasmosaurines, and I believe
some specimens show relicts of the fenestrae, although I'm not certain.

Jaime A. Headden wrote:
        Jaime! We are NOT discussing oviraptors! What are you doing here?!?! ;)

>
>*Zuni*--------\_
>*Ava*--\___   /
>*Cera*-/   \_/
>*Chasmo*-\_/
>*Centro*-/
>
>clade, then it might be more supportable for a new
>family to be coined for Chasmo and Centro, despite
>previous definition and diagnoses of these as
>Ceratopidae. Thusfar, we could get a new
>"Chasmosauridae" for this clade, and name the node
>that supports Zuni + Chasmo.
        Actually, Ceratopsidae == { _Triceratops_ + _Centrosaurus_ }, so
that would be the chasmo+centro node. Indeed, according to Sereno,
Ceratopsiane == { _Triceratops_ > _Centrosaurus_ } (contrary to DeQ&G's
suggestion concerning type taxa), so Ceratopsinae would not include _Ceratops_!

>  Highly supported groups appear to be the following:
>*Pachyrhino*-\_
>*Achelou*----/ \_
>*Einio*--------/
        Well, part of the reason for this is because there doesn't even
appear to be support for a separate _Aeschelosaurus_. I regard it
provisionally as a junior synonym of _Pachyrhinosaurus_. "Einiosaurus" is
problematic, but I'd provisionally keep it where it is.

>  with Styraco, Centro, and Mono as successive
>outgroups or a monophyletic sister assemblage
>(suggested by the recent JVP paper?),
        It seems likely, IMHO, that Styraco is closer to the above clade,
and that _Centrosaurus_ may in fact be paraphyletic (which doesn't
necessarily obviate it as a valid genus). 

>so a
>monophyletic grouping here can be supported; I believe
>"Pachyrhinoisaurini" (or -nae?) has been suggested. If
>there is a successive series, then naming a -ini, then
>a -nae, leaves at least two nodes empty and unnamable
>by modern convention.
        Actually, there is *no* convention I am aware of regarding this.
Those who still advocate the use of rank would, I'm sure, appreciate you not
naming those nodes, but for others there would be nothing wrong with naming
one of them, say, Styracosauroidea.

>*Tri*-\_
>*Di*--/ \_
>*Toro*--/
        "_Diceratops_"... what will they think of next?

>clade, whether or not you support Forster (1996) in
>removing *"T." hatcheri* from *T.*;
        Hah! If you know morphometrics, reread her article... it really
doesn't PROVE anything. It's still anyone's guess.

>Toro and Tri
>appear to be more closely related to each other than
>either is to any other "chasmosaurine", and with
>*Anchisaurus* the most basal (known) and the rest
>falling more or less serially. Penta, I think, has
>been supported as closer to Tri than is Chasmo,
>Arrhino, or Anchi, and if so, there are at least four
>unnamable nodes,
        I'd put arrhino with toro, or both serially toward tric (which one
first? Who knows...). It does appear that _Chasmosaurus mariscalensis_ is
closer to penta than is _Chasmosaurus belli_, but how these fellas clade out
relative to the others is anyone's guess. _Anchiceratops_ is a special case.
I'd put it closer to _C. belli_, but that's just a guess. Really,
ceratopsian phylogeny is awfully rough. I wonder why... :)

        Later,
        Wagner
--------------------------------------------------------------------------------
     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
  "Why do I sense we've picked up another pathetic lifeform?" - Obi-Wan Kenobi