----- Original Message ----- From: "Phil Bigelow" <bigelowp@juno.com> Sent: Monday, September 19, 2005 5:25 PM
And to be clear: I *loath* the idea of "redefining" a clade, and I hope that Phylocode comes up with rules that roughly parallel the rules for gen. sp. naming in the ICZN.
See below.
Once a clade has been defined in the literature, it remains that way forever (unless it has broken some other naming rule, such as priority, preoccupation, etc., etc.).
Example: If Padian and May's (1993) definition is ever formerly adopted, and if birds are later found to be outside of Dinosauria, then I would advocate just leaving Padian and May's clade name in place, and then creating a new clade that excludes birds. Call it Eudinosauria, or Owendinosauria, or something similar.
You'd lose a lot of people in that case.
But I would only advocate such a thing provided that all of the following criteria are rigorously met:
1) Artiodactyla is indeed monophyletic.
What degree of certainty would you like...?
3) The empirical evidence for cetaceans being members of Ariodactyla must be *overwhelming* (such as is the case with birds being dinosaurs).
Where to draw the line?
Just for the record, I suspect that the final version of Phylocode will require that a clade definition that uses a Linnaean name *must* use as specifiers only traditional members of that Linnaean group (you appear to believe this too).