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

[Michael Mortimer <mickey_mortimer111@msn.com>]

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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