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RE: Princeton Field Guide



Denver Fowler wrote:

<The point of having a robust taxonomy is to recognise diversity accurately: 
ie. how many independent lineages are present at any given point in time. 
Whether you split a lineage into multiple genera (Centrosaurines), species 
(Chasmosaurus), or just have taxon A, B etc (e.g. Horner et al, 1992), doesn't 
really matter, so long as you understand the diversity correctly. Naming 
everything as monospecific genera facilitates communication, and dealing with 
cladograms, but too often it also leads to false impressions of diversity that 
doesn't really exist.>

  I missed Scannella's talk (by not having attended) but I've read the 
abstracts presented on this topic, and I've read the paper on which thos talk 
is based (i.e., the *Triceratops* taxonomy one), so you will pardon me if this 
was brought up at all and addressed (by this paragraph quoted above, I will say 
"no."

  If you, or anyone, insist that "there is only one taxon" (Scannella and 
Horner, 2010) of ceratopsid in the Hell Creek beds of the Maastrichtian, then 
you are making an arbitrary lumping point without ANY sense of diversity 
measurement at all. It is also entirely inaccurate, as there are TWO "species" 
by Scannella and Horner's count, not one (that's two), a "genus" (three), a 
"subfamily" (four), and a "family" (five); if we want to conflate this further 
up by including other taxa (like *Leptoceratops gracilis*), we can go all the 
way to *Coronosauria* (which will include *Ceratopsomorpha,* *Ceratopsoidea* 
[if not explicitly than my extension] for six and seven) and *Ceratopsia,* 
*Marginocephalia,* *Genasauria*.... So there are quite a few "taxa" (some 
unnamed but implied according to the ICZN -- if you want to use ranks like 
"species" and "genus," which Scannella and Horner seem to do). Scannella and 
Horner, and Horner and Goodwin on *Pachycephalosaurus*, certainly do think 
there is a real quality that can be used called a "genus," and have insisted 
that each Hell Creek taxon was limited to "one" genus with as many species as 
seems to be suitable (see *Triceratops*).

  So when you conflate the idea of "diversity," but offer no means of measuring 
it objectively, then like Paul does, you start making arbitrary lumping actions 
that come under fire -- not because someone thinks you are treading on "their" 
taxon, but because it is SO _individually_ arbitrary; you are literally making 
up your mind taxon to taxon, rather than applying a suite of reasoned arguments 
you will then use objectively to any taxon you find. When the decision is made 
in this manner to "lump" a taxon (and then go make several press statements 
supporting this decision) I question the sense that "diversity" is in any way 
part of the decision-making process. This is largely due to the fact that 
"genus" has nothing to do with diversity, unless specifically defined as such, 
and no one has yet to formally perform a broad systematic "perspective" on hat 
happens if you make a "diversity"-based model for taxa using Linnaean taxonomy 
as your benchmarks for "levels" of diversity.

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)