Taxonomies dirty secret (was RE: The mystery of the furcula)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

[Decloaking.  Incidentally: AJ, look in your e-mail box after 7:30 pm for a
long-awaited something...]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> David Marjanovic
>
> > > Could you please explain what an order is? [...]
> > > What is a small group? [...]
>
> It's just that nobody
> whom I've asked so far, and nothing that I've read, has given me
> any answer
> to this (which is why I have to use phylogenetic taxonomy, in the
> absence of
> any alternative). I don't have the slightest idea whether you think
> Pterosauria and Pterodactyloidea might be way too big or way too
> small taxa
> to compare with Titanosauriformes; Mammalia is certainly too big,
> Cichlidae
> is probably too small, but what could be appropriate? This is not a
> rhetorical question. Really.

Dave (and everyone else): the dirty little secret of traditional taxonomy
(in which, I might add, I was trained for most of my undergraduate and
graduate career).

There is NO (count them, no) algorithm, metric, device, or other methodology
for assigning ranks, nor has there been in the past.  Ranks have been
assigned SOLELY on the basis of tradition, starting with Linne and
interpolating ever since.  Some would start a new tradition (i.e., break
Class Amphibia and Class Reptilia into two rather than a single unit; break
Class Pisces into several Classes; move the arthropod "Classes" up to Phylum
rank, and then back down again; etc.), but not on the basis of independantly
verifiable means.

There have been traditional "sensibilities" among workers in different major
taxa as toward how much variability (never quantified) should be encompassed
by a family, order, etc., but these sensibilities differ for each major
taxon.  So fossil reptile workers might agree artistically on how much you
could squeeze into an Order before you had to split it up, but that would be
independant of the malacologist or entomologists "Order Concept".

In what meaningful way is the Order Ornithischia equivalent to the Order
Lagomorpha the Order Perciformes to the Order Thoracica to the Order
Spinulosida to the Order Teuthoidea to... (you get the idea)??  Number of
taxa? Date of origination? Amount of variability?  Morphological distance
from the next equivalent rank?

People have suggested these as ideas, but only After The Fact; as possible
justifications for the rankings already established, rather than a principle
or metric by which the "rank" of a taxon could be evaluated.

It is not Science.  It never has been Science.  It is only Art and
Bookkeeping, and honest taxonomists admitted it.

> A way to compare the sizes of taxa would be
> very, very convenient (studies like "how many families of __ died
> out at __"
> would be possible this way, for example). So if you have an idea, please
> tell, I'd really like to know.

[Re-engaging cloak.  Silent running...  Will be back soon.]

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796