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Various and sundry: plesia, cladistic databases, outgroups, Eotyrannus 2 & 3, classification criticism



Greetings,

Below are short little responses to a number of different threads going on
the computer this morning. Rather than risk running out of available
messages early in the day, I'd thought I'd lump them all together:

>From Aspidel:
>So... What's a plesion?

A term coined by Patterson and Rosen (1977), who recommended that fossil
taxa should not be assigned the customary categorical ranks of their
(generally living) sister group, as this would lead to to an inordinate
increase in the number of ranks and/or quickly "inflate" the maximum rank
used in a particularly small part of the tree.  (Eldredge and Cracraft later
pointed out that you could in prinicple use it for living monospecific
higher ranks).  So "plesion" (plural "plesia") is a "place-holder" for a
traditional rank.  With the move to unranked taxonomy, plesia became
redundant and since abandoned by most working systemicists.

Henri Rönkkö writes:
>
> The cladists build cladograms by feeding data into a computer. I am very
interested in the
> data used to build cladograms of the Dinosauria. (Not the modern birds
especially.) As even
> on this list there are many scientists who have engaged themselves in the
art of
> classification, it occured to me that I might be able to get the data by
asking these
> particular scientists to send me some. So, would you please send me some
data, then? The
> proximal reason for my desire is that I'm making a treatise on bird
evolution. (For a good
> deal of time by now, indeed, and my efforts will likely extend to distant
future too.)

Many databases for particular phylogenies are available on the web,
particularly if they are part of the "Supplementary Information" provided
with the online version of a paper.  (Note that the "Supplementary
Information" is often freely accessible even if the paper might require some
personal or institutional subscription).  Sereno's 1999 databases are
online, as are those of various manuscripts by Xu Xing and colleagues,
Norell and colleagues, and others in recent years at Science and Nature.  My
own Gaia paper matrix, with data for Confuciusornithidae, Protarchaeopteryx,
and Caudipteryx added, will be available online from Yale Press once the
Ostrom Symposium volume is out; I'll let you know when that happens.  There
will be other databases available with that volume, too.

Morgan Churchill writes:

> Number two: what was the height of Eotyrannus, as compared to say a human.

About 2 m high at the hips, based on Naish's reconstruction.

> Number three: How probable/improbable would it be to depict Eotyrannus
with some sort of
> feathers.  I know the recent illustration by Todd Marshal gave it a sort
of atrophied
> plumage; would this be reasonable

Plumage is inferred because tyrannosauroids seem to be more closely related
to birds (in at least some studies) than is Sinosauropteryx, a form known to
have primitive protofeather plumage.

Ken Kinman writes:
>
> Dear All,
>       I finally decided to update my classification of
> Ornithischiformes.

[table snipped]

> Constructive criticism is welcome.

I hope this is taken in the spirit it is intended, but my suggestion is that
you leave creating taxonomies to people with first hand familiarity with the
specimens and the literature involved.  That has been the practice in
taxonomy for many generations, and should go doubly in the age of the
Internet.  Unsuspecting non-systemicists may find your (as I am sure you
would admit yourself very preliminary) work on the Web, and might use it in
future compiliations, textbooks, etc.  Mickey Mortimer has already pointed
out (and rightly so) that he was uncomfortable with you using his analysis
for the basis for a classification scheme, as his own work has not been
examined by others nor is based on direct evaluation of the specimens in
question.  I strongly urge anyone who does post classification schemes here
or on your own website that are not based on professional-level studies to
have some clear information on the same posts/pages SAYING that these are
not the results of professional-level studies.  At the very least, you
should have citations on the same page for the sources of the information
presented.

                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