RE: Cladospeak: Bonnan errata and corrections

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dinogeorge@aol.com
>
> Well, indirectly. Groups are now >defined< in terms of phyletic
> relationships, e.g., common ancestor  of x and y plus all its descendants
> (node group) or all organisms more closely related to x than to y (stem
> group). Once a group is defined, the problem is to figure out
> whether a given
> organism is in the group or out of the group, and that's where
> the characters
> come in.

Agreed.

> I support this method of doing taxonomy, although it has not yet
> been taken
> to its logical conclusion in many instances (e.g., accepting Peter Ax's
> definition of stem-group birds as including dinosaurs).

Actually, your example is not necessarily the "logical conclusion".  There
would be nothing programmatically incorrect with regards to such a
definition, save for the fact that there already are precedants and
priorities set for the stem-group of birds and everything closer to them
than to crocs; for the name "Aves" and "Avialae" and "Neornithes"; and for
"Dinosauria".

That is to say, the logical conclusion is to give formal phylogenetic
definitions to taxon names; it is not neccessarily to give a stem-based
definition for all well-loved, well-known names.

                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