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tyrannosaur implosion; useful classifications
Mickey, George, and others,
I feel that I have also contributed in a small way to the tyrannosaur
implosion (but at a higher taxonomic level). As far as I am concerned
Tyrannosauridae sensu lato is quite adequate, and Tyrannosauria and/or
Tyrannosauroidea are unnecessary splitting. Furthermore, the content of
these latter taxa could vary in the future, since their definition would be
cladistically fixed, so they just complicate the literature.
Easier just to have one formal Tyrannosauridae, and when a new genus
like Eotyrannus comes along, the family just grows to accomodate the new
form. Or alternatively, the family stays the same and we add a Plesion
Eotyrannus as its sister group. We don't need all these clade names choking
up the nomenclatural system and causing this obvious confusion. It's just
too destabilizing and too much of a straight-jacket.
And finally I must counter the charge that I am being too typological
as a traditionalist eclecticist. The way I see it, having just one type for
a taxon gives me some flexibility. Strict cladists, on the other hand, feel
more comfortable with two or more types (euphemistically called specifiers)
which only provides stability of definition. Unfortunately it restricts
flexibility and also can severely destabilize taxon content.
Whether you call if being typological, or specifilogical (to use a
euphemistic neologism), I think you are unnecessarily restricting
flexibility and usefulness, and perhaps even increasing overall instability
as well. Isn't it interesting that my more concise classification of
Ornithischiformes is sparking a useful discussion of phylogeny, perhaps
because its very conciseness makes phylogenetic problems so readily
apparent. You are less likely to get such discussion when faced with an
oversplit and cladistically confusing classification or even cladogram. I
can only reiterate that there is more than one way to cladistically skin a
cat (or any other taxon).
So in the interests of long-term stability, I hope the appropriate
PhyloCode committee will consider assigning the current definition of
Tyrannosauroidea to Tyrannosauridae instead. I believe it is (according to
Keesey's terminology) as follows:
Tyrannosaurus > Ornitholestes, Neornithes.
Whatever clades exist within this broader family can be defined with
reference to subfamilial names (subfamilies, tribes, or whatever). If the
lower taxa are imploding, why not implode the higher taxa a little and avoid
conflict with traditionalists?
Subject: Re: Digit Loss
Date: Sat, 9 Jun 2001 02:59:13 EDT
In a message dated 6/8/01 7:49:32 PM EST, Mickey_Mortimer11@email.msn.com
<< George Olshevsky wrote-
> The describers keep Eotyrannus outside Tyrannosauroidea
> (whatever that is these days) as a sister group, so to this extent our
> phylogenetic hypotheses agree.
Actually, the authors place Eotyrannus within the Tyrannosauroidea, which
defined as all taxa more closely related to Tyrannosaurus than to
Ornithomimus or Deinonychus. >>
Right, so they did. At one point I thought Tyrannosauroidea was
Aublysodontidae plus Tyrannosauridae (though now I think Aublysodontidae is
just juvenile/subadult Tyrannosauridae), and they do exclude Eotyrannus
that. Hence the phrase "whatever that is these days" above. Their def of
Tyrannosauroidea is more or less my def of Tyrannosauria.
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