Re: Acme genericometer (was RE: Gorgosaurus (was RE: Daspletosaurus t emporal...

[Dinogeorge@aol.com]

In a message dated 8/7/02 2:08:22 PM Pacific Daylight Time, 
TiJaWi@agron.iastate.edu writes:

<< 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.>>

I'm perfectly happy with paraphyletic genera (and higher taxa). Otherwise 
Homo is simply a subgenus of some unicellular eucaryote genus.
 
<< (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. >>

I addressed this issue in my Dino Frontline article on tyrannosaurids and 
later in my email on the tyrannosaurid implosion. AFAIK lacrimal horns occur 
only in the genus Albertosaurus, which is derived relative to Tarbosaurus and 
all other known Asiatic tyrannosaurids. It's still an open question (to some, 
anyway) whether Tyrannosaurus derives from Albertosaurus or Tarbosaurus; if 
the former, then the lacrimal horn was secondarily lost in Tyrannosaurus, if 
the latter, then the lacrimal horn never appeared in Tyrannosaurus.