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Acme genericometer (was RE: Gorgosaurus (was RE: Daspletosaurus t emporal/stratigraphic range))

> Meanwhile, my own genericometer sees Albertosaurus, Gorgosaurus, and 
> Daspletosaurus as three distinct species of the genus Albertosaurus. One
> diagnostic character uniting them is the presence of a lacrimal horn
> that protrudes above the skull table. 

Two points:

(1) Check the manufacturer's instructions for your genericometer.  Before
your genericometer can even be switched on, you have to first demonstrate
that the species constitute a monophyletic group.

(2) The assumption that the lacrimal horn is a derived character that unites
certain tyrannosaurines (sarcophagus, torosus, libratus) to the exclusion of
other tyrannosaurines (remotus, rex, bataar) has to be shown to be superior
to competing scenarios e.g. that the lacrimal horn is a primitive
tyrannosaurine character that was lost in rex, bataar and remotus.



Timothy J. Williams, Ph.D. 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 9359