RE: Class Dinosauria?

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Hector Rivera Sylva
>
> I would like to know what is more acurate, to place
> the Dinosauria as a Class or as a Superorder of the
> Class Reptilia.
>
YIKES!

That opens a very, very large can of worms. This topic has been discussed
many, many times on the list: one can consult the archives at
http://www.cmnh.org/dinoarch/index.html.

To summarize, though:
*Many modern biologists interested in the classification of living things
have abandoned the concept of "ranks" (like Classes, Orders, etc.) as
outdated, pre-evolutionary concepts.
*Instead, we recognize a series of internested groups, but don't assign
these groups "ranks".
*So, Dinosauria is a clade within Reptilia, and Aves is a clade within
Dinosauria within Reptilia.  This more accurately reflects the evolutionary
relationships of these groups.

You may want to check out, among other readings, my chapter in Dinosaurs:
The Science Behind the Story:
http://www.geol.umd.edu/~tholtz/tyrdeintree.pdf.

I hope this helps,

                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