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Re: Acme genericometer (was RE: Gorgosaurus (was RE: Daspletosaurus t emporal...
In a message dated 8/7/02 2:08:22 PM Pacific Daylight Time,
<< 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
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.