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Re: Diagnostic Material

Yes, there will always be varying opinions; some things are clearly diagnostic, 
others are clearly not, but there will always be gray areas.

It certainly can't be done by number of bones - just saying "a specimen 
composed of one vertebra/whatever can't be diagnostic" doesn't work, because of 
stuff like <i>Xenoposeidon</i> - one partial vertebra, tons of distinctive 

----- Original Message -----
From: "Thomas R. Holtz, Jr." <tholtz@umd.edu>
To: VRTPALEO@usc.edu
Cc: "Dinosaur Mailing List" <dinosaur@usc.edu>, "vert paleo mailing list" 
Sent: Thursday, April 15, 2010 6:25:18 AM GMT -06:00 US/Canada Central
Subject: Re: Diagnostic Material

Jaime Headden wrote:
> Â Greg Paul's recent notification of his and Carpenter's appeal to the
> ICZN has left me with a question (previously posted, but perhaps not
> pointed in the right direction).
> Â I am rather intrigued by any use of "not diagnostic," or the conclusion
> that a specimen is not complete enough to be diagnostic. This lends the
> very meaning of the word "diagnostic" in question.
> Â I thus ask what, if any, definitions for the term "diagnostic" are
> available for specimens (either as types, for referral phylogenetically,
> or determination for completeness)? It seems a fairly important question
> that is both raised and left out of the application by Paul and Carpenter,
> and I am sure there are other people just as interested as I in this
> apparently important scientific, yet seemingly underdefined term.

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.

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.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA