Re: dwarf tyrannosaurus

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

 From: "Considine, Blaise" <BPC.APA@email.apa.org>
 >
 > If nanotyrannus is a dwarf species of tyrannosaurus, why would it need to 
 > be named T. lancensis?

Because that is the species name it was first given, and priority
rules *seperately* at the genus and species levels. Thus, even when
placed into a new genus, a species retains its original species name.
Since the species was described *many* years ago as Gorgosaurus
lancensis, the name is probalby going to remain lancensis.

[Bakker merely erected a new genus, Nanotyrannus, for this previously
described species - if it turns out to be a species of Tyrannosaurus,
then the genus Nanotyrannus becomes a junior synonym of Tyrnnosaurus].

 > Is there already a dwarf species named? 

No, there are only two species of Tyrannosaurus at this time,
T. rex and T. bataar.  Both are very large.

 > And, if 
 > I've been following this naming thread properly, wouldn't nanotyrannus 
 > stick?,

Not if it is held to be a species of Tyrannosaurus.  It only sticks
as long as the species is held to be in a seperate genus.

And, since size is considered to be a very *minor* feature in
taxonomy, a species that differs *only* in size from some other
species simply does *not* belong in a seperate genus.

But this all depends on the lack of autapomorphies in G. lancensis
other than minor ones like size or the shape of the skull ridges.
[Since the skull ridges in tyrannosaurids are species recognition
characters, they are expected to change rapidly and noticably
between any two species].


Note, Tyrannosaurus is not the only possiblity here.  Depending
on its actual phylogenetic position, and on the acceptance of
Gorgosaurus again as a genus, the species might be placed in
Albertosaurus or even returned to its original position in
Gorgosaurus.

I just suggested Tyrannosaurus since Dr. Holtz cited one
expert as claiming it had no significant difference from
Tyrannosaurus.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.