Re: Def. of Ornithischia

[Jeff Poling <jpoling@dinosauria.com>]

At 04:17 PM 6/11/97 -0400, Thomas R. Holtz, Jr. wrote:
>"Triceratops and all taxa sharing a more recent common
>ancestor with Triceratops than with birds": Padian and May, 1993.
...
>While on this subject, the node joining Pisanosaurus and Genasauria (or
>Lesothosaurus and Genasauria) has not been named.  "Predentata" might be
>used as a node-based taxon using either of those definitions.

   One question about phylogenetic naming conventions and priority.  Stem
based definitions exclude the most recent common ancestor of the taxa in
question.  Since clades are supposed, if I understand correctly, to be the
monophyletic representation of taxa and their ancestor, shouldn't node based
definitions therefore be the ones used, and have the priority?

   In other words, why wouldn't a node based Predentata of the most recent
common ancestor of, say, Pisanosaurus and Triceratops take precedence since
node based taxa seem to be the underlying principle of cladistics?

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