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RE: Diagnostic Material

Tom Holtz wrote:

<It is fairly straight forward, but sadly (like much in this world) a relative 
term subject to change with new information.

Diagnostic = possesses traits sufficient to distinguish it from other taxa 
known at the time of the initial write up of the specimen and coining of the 
new taxon.>

  This definition is problematic. Any time a new taxon is described for a given 
clade, the relative diagnosticity (or whatever) of the material of an earlier 
named taxon reduces, such that it becomes _less diagnostic_ for its own taxon. 
Extending this through time, we'd expect even a "new" fossil to be so limited 
in its uniqueness that the material could be complete and still nondiagnostic.

  The term as I've seen it used also refers to the capability of determining 
differentiable features, regardless of whether they are autapomorphic, so long 
as they are apomorphic. This is how Paul and Carpenter use it, but they extend 
this definition (without using any) to the suite of material they discuss. So 
the argument seems to also suggest that a certain amount of material cannot be 
diagnostic, regardless of the associated viability of that material.

  For example, several aetosaurs are diagnosed originally on the basis of a few 
bits of armor, and despite decades of research, this material remains unique in 
some apomorphies to permit the material to be diagnostic (aetosaur armor being 
very differentiable to a certain degree, which some have split to the specific 
level). It has also been used to support sauropod dinosaurs, in that there are 
more than a few named on the basis of only a dorsal vertebra, portions thereof, 
or a series of a few dorsal vertebrae.

  If we extend the argument of Paul and Carpenter to a percentage based value 
to how much of a given amount of material is diagnostic, then we can assert 
that each of these singular elements makes up, say, a percentage of the 
skeleton (and as they can be coded for apomorphies, we can use Mannion and 
Upchurch's recent CSM to quantify the value for the specimen. If I were to 
acquire a humerus of a theropod dinosaur, and I can split the humerus into 
about 45 discrete apomorphic values (and I can) half of a humerus should 
reasonably be supportive of half that many characters to score, making its 
comparable value relatively higher than a phalanx (unless I can apply more 
apomorphies to a phalanx). This would support high values for some bones, lower 
for some, but it becomes compounding when you have scattered elements of a 
skeleton, and thus the comprehensiveness of the material increases.

  It is likely not arguable that YPM 1930 is diagnostic under the definition of 
lacking autapomorphies, but it is hardly true that it lacks apomorphies, and as 
such, that it can be determined as likely belonging to *Allosaurus fragilis*, 
regardless of whether it can be applied to *Allosaurus* sp. vide Chure, one can 
say the material is diagnostic (it can be applied to *Allosaurus*. Were it crap 
without any differentiable qualities, then I'd say it was essentially 
nondiagnostic, but such material you only find in things LIKE crap, sensu 
dinosaur dung containing bone bits.

<The problem is that greater numbers of taxa (and/or variation within taxa) are 
discovered, what was once a unique set of traits may be found to be much more 
widely distributed.>

  We all know we'll eventually discover all potential species, or at least 
until people start oversplitting out of boredom.
The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with