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

Mickey Mortimer wrote:

<Sure comparability is limited, but that's an unfortunate reality of vertebrate 
I think any attempt to assign a threshold value for taxonomic nomenclature is 
naive.  A single fragment could preserve an autapomorphy while much larger 
sections of the skeleton could be indistinguishable from two other similar 
taxa, given our current knowledge.>

  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 

<And that latter qualifier is an important argument against Mannion and 
Upchurch's value where the "gross number of definable characters relative to 
the body region/skeleton can ... be used", since this is dependant on the 
extent of published studies at any given time. Take tyrannosaurid pes 
characters for instance.  Looking at any published matrix or most published 
descriptions, you would get the impression that within Tyrannosauridae, the pes 
structure is basically useless for distinguishing taxa besides larger genera 
having more robust bones. Yet as part of his reexamination of Alectrosaurus, 
Carr (2005) found 163 pedal characters that varied among tyrannosaurids.  All 
of a sudden, there's hope for "Ornithomimus" grandis whereas before everyone 
would say "it's just a metatarsal III - instant nomen dubium!"  Maybe 
ceratopsid orbital horn cores are similar if someone examines them more 
closely, maybe they're not.>

  To be fair, the value in M&U, 2010 is recalculated. Mannion and Upchurch took 
the four most recent, substantive analyses into account to assess their 
character completeness index (CCI), and it is certain that one could take each 
analysis, each specimen, and calculate the relative quality of the specimen to 
the analysis, and generalize to other analyses (and they did). M&U also do not 
argue that the size or number of "informative" characters is relevant, just 
their number, and this refers to a CCI. What does the value of phylogenetically 
informative material have in relation to the value of the percentage of a 
skeleton? No one has done this work, but you want to use one to contradict the 
other, and they hardly measure the same thing. This is especially important 
when in the space of little time, one can find massive informativeness 
recognized in a small system of bones versus realizing that none of the bones 
have any informativeness whatsoever, but the information used to differentiate 
taxa is integumental. What do you do then? (We're lucky most of our 
considerations are skeletal, so the issue is generally mooted, but it becomes 
increasingly more difficult as we near crown taxa and their 
nonskeletal/skeletal components "informativeness" ratio is highly distinct -- 
based as it is on recognized characters.)

<Your objection that the taxa above are only temporarily diagnostic, pending 
the discovery of two or more specimens that both show their supposed 
autapomorphies, could be applied to any taxon.  Say we found two Gorgosaurus 
specimens that preserved an amazing amount of skin impressions that indicated 
they were different species.  Suddenly Gorgosaurus libratus is a nomen dubium 
because its holotype doesn't preserve skin impressions, despite being a 
complete skeleton.  Or if Djadochta Velociraptor turns out to be two taxa that 
differ in several pelvic and hindlimb characters.  There goes Velociraptor 
mongoliensis, since the holotype is just a skull and two manual phalanges.>

  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? And note that I never 
determined a strict value for nomina dubia; I argued that some of the taxa that 
are recognized today, based on a single bone, could be considered nomina dubia 
on the basis that "sufficiently diagnostic" had a value, and these specimens 
did not reach it. I currently don't regard any taxa as nomina dubia because, as 
stated before on this list, the definition for "nomen dubium" is highly 
subjective, and "diagnostic" is undefined and subjective.  Formulating a basis 
for either may result in some, but maybe not all, of these taxa to become 
nomina dubia. And what would that mean for nomenclature? That's also subjective.

  What does that give us?

<That taxonomy will inevitably change as we discover more specimens is no 
reason to stop trying our best now with the data at hand.>

  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.

<Might as well just call a moratorium on phylogenetic analyses until we have 
discovered all the preserved specimens and dedicated several centuries to 
teasing out all their variable data and perfecting phylogenetic algorithms.  
After all, the trees we'll make then will make today's pale in comparison.>

  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. Where your work and mine 
might coincide has a lot to do with something I discussed yesterday: My paused 
humerus study. We could easily take each bone and plug every named dinosaur for 
which that bone is known and assess them in a cladistic matrix. The output 
would NOT be a phylogenetic proxy. It is almost certain that were we to exclude 
all cranial material from the TWG matrix as it stands in its most complete and 
latest published form (which I think is in Choiniere et al on *Haplocheirus 
sollers* although I might be incorrect) the analysis would be substantively 
different from that of the total inclusion matrix. 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.


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 
The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with