RE: Definitions

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Steven Mahon
>
> > Dinosauria is _Triceratops_, Aves, their most recent
> > common ancestor, and
> > all of its descendants (Padian and May, followed by
> > Sereno 1997; however, a
> > second school holds a definition _Iguanodon_,
> > _Megalosaurus_, their most
> > recent common ancestor, and all of its descendants).
>
> What do you mean by second school?

As in "a second school of thought" or "another batch of folks".  Including
one Thomas R. Holtz, Jr... :-)

> > Sauropodomorpha is _Cetiosaurus_ and everything
> > closer to it than to Aves
> > (Padian et al. 1999) OR _Plateosaurus_,
> > _Saltasaurus_, their most recent
> > common ancestor, and all of its descendants
> > (Sereno).
>
> I thought it was Saltasaurus > Aves? Is there
> something I'm missing?!

Sereno 1997, 1998, and 1999, and Wilson and Sereno 1998, are all pretty
clear in using a node-based definition.

> I also had heard that there might be a Dinosauria
> definition that includes Herrerasaurus. Does it really
> exist?

D'OH!! Yeah, Gauthier 1986, where Dinosauria is the clade that contains
Herrerasauridae, Ornithischia, Sauropodomorpha, and Theropoda. Note that
this paper was developed prior to the literature on phylogenetic taxonomy,
so some of the clades are not given a formulaic definition. Therefore, we
can't tell if this is a node-based or stem-based group.  (Incidentally,
following this version of Dinosauria and the then-accepted hypothesis that
herrerasaurids were outside the remaining dinosaurs, Novas named
"Eudinosauria" for Ornithichia + Saurischia.)

> Also, I don't think I should have make a page for
> every taxon. What main clades *should* I make pages of
> that would represent the major clades well?

Your own call there. I could envision several different versions.

                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