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RE: Ceratops (was RE: Glishades ericksoni, ...)



Mickey Mortimer wrote:

<Er, if you're comparing a middle and a distal caudal, you're not 
comparing homologous elements so it doesn't matter. If you find them 
both to be distinct from other taxa in different ways that don't lead 
you to conclude they belong to the same taxon (but they in fact do) then
 you made a mistake.>

  It is hardly a mistake when, if the two elements are differentiable 
(pneumatic chambers, extra spines, laminar complexes, extra ridges on the 
sides, absence of apophyses, haemal facet morphology, etc.) then -- ergo -- 
they are different. It matters not that they can be the same taxon here; you're 
applying the "mistake" of differentiating them taxonomically through hindsight, 
and this is fallacious when trying to assume in the "now" of science that what 
you have recovered is NOT the same as someone else's taxon (or your own). They 
do not belong to the same taxon until someone comes along and refers them all 
to one another (and this deserves the same level of scrutiny and ridicule as 
the preceding strategy).

<In the case of Anomalocaris, the scientists were mistaken about which 
body part the specimens belonged to.>

  The scientists in question were not even aware that some of the body parts 
they were describing even existed in an animal. They described *Anomalocaris* 
as a "shrimp" based on a grasping appendage, then later found a specimen that 
connected various bits; even then, from the same horizon one did not expect all 
anomalocarids to be *Anomalocaris,* or that all anamalocarid radulae or 
appendages would belong to that taxon. This is, if anything, a grand example of 
why partial or distorted specimens should not serve as types, but they do (even 
when scientists think that they have more complete material based on incomplete 
information).

<Why NOT name a taxon you think is distinct? Is having a name synonymized
 or later rejected as indeterminate such a horrible thing? Happens all 
the time.>

  I'm a bit wary of the topic, personally. Perhaps this makes me taxonomically 
conservative. I'd really rather be involved on the descriptive, analytical side 
of things. Here's a dirty secret: If I was involved in a new paper describing a 
new animal, if it was an issue, I'd rather NOT be involved in the nomenclatural 
act (i.e., the authorship of the nomenclature would differ from the total 
authorship in which I was a part). Perhaps it makes me more comfortable not 
being involved in nomenclature that can be overturned, but I am not so egoistic 
that I want my name on taxonomy in that manner -- at least that's how I see it 
(some taxonomy certainly seems egoistic).

  However, when it comes to even differentiating securely distinct specimens 
taxonomically, it had better be a pretty darned securely differentiable 
specimen (separable from as many specimens as possible). Such a specimen might 
even be the new *Azhendousaurus madagaskariensis*, which instead of being 
represented by a partial mandible from Morocco like *Azhendousaurus laaroussi*, 
it is represented by a bonebed in the Isalo series [1] -- and yet, despite 
this, the holotype is not a "type series" but is a posterior section of the 
skull, including braincase and circumorbital region, which permits a lot of 
comparability and anlysis by itself.

<Having our ideas potentially rejected later is the price we 
scientists pay for presenting them in the first place.>

  You have an interesting and displeasing sense of fun.

<I meant we'd "lose" the taxa in the sense that they would become nomina 
dubia, since they would be inseparable from both newly recognized 
species.>

  I am not particularly fond of the term _nomen dubium_, and have for the most 
part restricted it to a specimen that prevents comparability by its condition 
or extent when I do use it. I tend not to use it based on the idea of 
"diagnostic" simply because that term itself is undefined. Othweriwse, taxa are 
not "lost," they still exist and we can still pretend that they matter. It 
amazes me, and maybe I can write something about it, that people think that 
when they write the opinion "Because I think [A], then [B] isn't real, and I 
want you all to use [C] instead," it has some sort of enforcable quality to it. 
Just like a taxonomic hypodigm, a taxon's existence is temporally relevant: it 
can increase or decrease in content as time goes on. In the end, there's only 
one good rule when using a taxon: It's only as good as the holotype.

<I think including Ceratops in such an analysis would have both 
advantages.>

  I actually agree with this. This might be relevant when I remarked earlier 
that the number of characters that can be calculated for a specimen _can_ be 
used to help define a specimen's diagnosability (or, I don't know, the word 
"diagnosis").

[1] Flynn, J. J., Nesbitt, S. J., Parrish, J. M., Ranivoharimanana, L. & Wyss, 
A. R. 2010. A new species of *Azendohsaurus* (Diapsida: Archosauromorpha) from 
the Triassic Isalo Group of southwestern Madagascar: cranium and mandible. 
_Palaeontology_ 53:669-688.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"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 
Backs)





----------------------------------------
> Date: Mon, 17 May 2010 03:20:34 -0700
> From: mickey_mortimer111@msn.com
> To: dinosaur@usc.edu
> Subject: RE: Ceratops (was RE: Glishades ericksoni, ...)
>
>
> Jaime Headden wrote-
>
>> Yes, it is possible for a single bone to be highly apomorphic, but this is 
>> highly dependant on the definition of your own personal metric and the 
>> meaning you apply to "diagnostic." If I recovered a middle caudal and a 
>> distal caudal, I could make the reasonable argument that, if the two bones 
>> differed, they could be different taxa. This begs against the "reasonable 
>> certainty" of the descriptor, but not only is it possible, it has been done 
>> for terrestrial vertebrate fossils, as well as for *Anomalocaris,* among 
>> other taxa. Thus even if the caudal vertebrae were diagnosable from one 
>> another, using the broadest sort of definition that equates to the base 
>> definition for "differentiable" in that they could be consider 
>> non-identical, one doesn't necessarily think this is viable, does one? The 
>> more we separate small bits into taxonomic chunks (even while considering 
>> the material could apply to other taxa, which adds another level of caution 
>> some authors have regarded, but chosen not to take into account) the more we 
>> leave ourself to potential [hedging bets here that it is not actual] data 
>> that overturns our findings. We leave ourselves open, and preciesly for what 
>> reason? What could we have done with the material without naming it? A 
>> specimen label is often just as useful as an italicized taxonomic label; in 
>> many respects, a specimen label is the same as a taxonomic label, but it 
>> does not purport to differentiate with or collect other material under its 
>> conceptual envelope; one could thus imply that the purpose of the taxonomic 
>> label has more social (communicative) or political (notoreity) effects that 
>> are preferred.
>
> Er, if you're comparing a middle and a distal caudal, you're not comparing 
> homologous elements so it doesn't matter. If you find them both to be 
> distinct from other taxa in different ways that don't lead you to conclude 
> they belong to the same taxon (but they in fact do) then you made a mistake. 
> In the case of Anomalocaris, the scientists were mistaken about which body 
> part the specimens belonged to. That happens in dinosaur studies as well. 
> Look at Chingkankousaurus- described as a scapula, but probably a rib. In 
> these cases, mistakes were made. I suppose where we differ is that I don't 
> see why making such a mistake is a huge problem. Why NOT name a taxon you 
> think is distinct? Is having a name synonymized or later rejected as 
> indeterminate such a horrible thing? Happens all the time. Having our ideas 
> potentially rejected later is the price we scientists pay for presenting them 
> in the first place.
>
>> I'm not quite sure I explained this clearly enough in the previous post: 
>> Temporal diagnostic value is unvalued at present. While we have incomplete 
>> types for *Velociraptor mongoliensis* and *Gorgosaurus libratus*, if the 
>> material belonging to the former is not sufficient to explain the 
>> variability in the collection, then yes, it implies the taxonomy is 
>> insufficient; but how do we "lose" any of these taxa under that basis?
>
> I meant we'd "lose" the taxa in the sense that they would become nomina 
> dubia, since they would be inseparable from both newly recognized species.
>
>> The current system is not a "system" so much as a convention: Subjective 
>> concepts of diagnostic characters lead to subjective concepts of taxonomy 
>> lead to subjective concepts of the diagnosability of other taxa, which leads 
>> to the subjective nature of characters used to evaluate specimens. This is 
>> circular, and insubstantive. And it is certainly not the "best we have to go 
>> with," an argument that is used to sustain historical conventions such as 
>> the Linnaean System, something I address on my blog; and nor are we "trying 
>> our best," when we make excuses, often outside of any methodology, or invent 
>> the thing on the spot, to promote the taxonomic scheme.
>
> I agree the current system is subjective, but I don't think an objective 
> system is possible at the moment. There are disagreements as to whether 
> extant species (whose full anatomy, behavior and genetics can be observed) 
> are valid, since the concept of a species itself is subjective. While the 
> Linnaean hierarchy adds to that subjectivity, any attempt to label 
> populations is going to be a personal choice. How much divergence is 
> necessary? How much interbreeding is allowed, and how theoretically possible 
> and/or unsuccessful must it be? So when it comes to the paltry remains of 
> Mesozoic dinosaurs we have available, I'm happy to admit it's all subjective.
>
>> I think this misses the point. I'm talking about taxonomy, and you're 
>> talking about phylogenetics. I discuss the ability to differentiate 
>> specimens, you want to plug anything into a matrix and see where it goes.
>
> The point was that it was an analogy, the common ground being that both 
> situations (you implying we should not name taxa if there's a decent chance 
> they'll become invalid in the future; me proposing the ridiculous moratorium 
> on phylogenetic analyses until all the data are in) state that we should be 
> too cautious to do science because it will plausibly be found to be incorrect 
> in the future.
>
>> Returning to something Tim Williams said earlier, including *Ceratops 
>> montanus* in a matrix leads us to including a specimen that is almost 
>> certainly difficult to differentiate as described from *Albertaceratops 
>> nesmoi* but also perhaps *Avaceratops lammersorum,* we could cause a 
>> collapse where it would be equally parsimonious that *Ceratops montanus* was 
>> *Albertaceratops nesmoi* and *Avaceratops lammersorum.* We could even make a 
>> phylogenentic prnouncement that they form a clade, or are the same taxon 
>> (ignoring potential differentiation), but this certainly doesn't tell us 
>> anything new simply examining the material wouldn't as well.
>
> Well, no phylogenetic analysis strictly tells us anything that simply 
> examining the material couldn't, it just makes it much easier to analyze and 
> more objective. I think including Ceratops in such an analysis would have 
> both advantages.
>
> Mickey Mortimer
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