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Re: Taxonomic Rant (was Re: SERENO'S NEW DINOSAUR PAPER)



In a message dated 97-07-02 19:12:04 EDT, th81@umail.umd.edu (Thomas R.
Holtz, Jr.) writes:

<< Essentially.  And, in hindsight, there isn't any problem using the type of
 _Iguanodon_ to anchor the taxon: although there might be question as to the
 interrelationships WITHIN the Iguanodontia, the Weald teeth clearly come
 from iguanodontian euornithopod ornithopod ornithischian dinosaurs and not
 from any other kind of animal. >>

I would say it's better taxonomically to anchor a taxon to a well-known
species rather than to a potential _nomen dubium_ (get this: a "potential"
_nomen dubium_[!]--a taxon about whose doubtful nature there is doubt),
_ceteris paribus_. There are better-known iguanodontian euornithopod
ornithopod ornithischian dinosaur species than _Iguanodon anglicus_; why not
use them? Again, I'm just playing devil's advocate here.

Incidentally, all you really need here is "iguanodontian," not the whole
euornithopod, etc. shebang, since we already know the whole shebang includes
Iguanodontia as a subclade. And--don't we have stuff like "dryomorphan
styracosternal ankylopollexian" stuck there in between the "iguanodontian"
and "euornithopod"?

I discuss the "too-many-names" problem of cladistic taxonomy in _Mesozoic
Meanderings_ #2. This business of naming a major node after excluding but a
single basal genus from a more-inclusive major node can get really
nightmarish, and it's not really necessary. As I point out in that
discussion, any binary cladogram with N terminal nodes always has N-1 branch
nodes, and since every branch node may correspond to at least three different
clades (node-based, stem-based, or character-based), there are at least
3*(N-1) potentially nameable clades in any cladogram with N terminal nodes
(>more< if there is more than one key character acquired between the branch
node and its predecessor). There is a real need to cull "useful" taxa out of
the great swamp of "nameable" taxa and not to name everything. Give them
internal letters or numbers or something if you desperately need to
distinguish them in a paper: subclade A, subclade B, etc. Decide on a name
only if the same unnamed subclade X keeps showing up repeatedly in people's
papers.