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Re: tyrannosaur implosion; useful classifications
Ken Kinman wrote-
> I feel that I have also contributed in a small way to the
> 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
> cladistically fixed, so they just complicate the literature.
I actually agree with Ken here, in principle. In many cases, restricting
clades to node-based groups is a bad practice in my opinion. For instance,
there has been a recent controversy as to the definition of
Oviraptorosauria. Some would have it be (Chirostenotes + Oviraptor), a
group which I call Caenagnathoidea. The problem is, this would exclude
Caudipteryx, Microvenator and possibly Nomingia from the Oviraptorosauria.
These taxa are obviously closer to Oviraptor than to segnosaurs, but there's
no clade name that would show this easily. I think node-based definitions
should only be made when a sister group relationship between two taxa is
being emphasized, but when a group is being defined just to contain some
taxa, keep it stem-based. Same thing for Ornithomimosauria (Pelecanimimus +
Ornithomimus). Just because Pelecanimimus is the most basal ornithomimosaur
found before the phylogenetic definition thing caught on, we'll never have a
more basal member. We shouldn't limit taxa just because we haven't found
more basal members yet.