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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?
-------Ken Kinman
*******************************************************
From: Dinogeorge@aol.com
Reply-To: Dinogeorge@aol.com
To: dinosaur@usc.edu
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
writes:

<< 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 is
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 from
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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