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Re: Ornithopoda + (Heterodontosauridae + Marginocephalia) phylogeny

Tom Holtz wrote:

Can't say I much like a Neornithopoda that doesn't necessarily include
Camptosaurus, Iguanodon, and the hadrosaurids (i.e., the critters for whom
the clade was originally coined), but it isn't explicitly defined here.

Frankly, I can't think of a *less* appropriate name for a Heterodontosauridae + Marginocephalia clade than "Neornithopoda". It reminds me of one of Kurochkin's classifications of Aves, which proposed the name "Euornithes" for a clade of enantiornithine birds. Very peculiar. It reminds me of another pet peeve of mine in archosaurian systematics: having the Suchia (crocodiles &c) as a clade within the Pseudosuchia.

Anyway, back to the proposed Heterodontosauridae + Marginocephalia clade. One course of action would be to define a node-based Heterodontosauria as "all descendents of the most recent common ancestor of _Heterodontosaurus_, _Triceratops_, and _Pachycephalosaurus_". If heterodontosaurids are ornithopods, then Heterodontosauria would become a heterodefinitional junior synonym of Cerapoda. If heterodontosaurids are linked to marginocephalians to the exclusion of ornithopods, then Heterodontosauria comprises Heterodontosauridae + Marginocephalia.

However, I don't know how Ornithopoda is defined - is it stem-based or node-based, and if node-based is _Heterodontosaurus_ one of the anchor taxa? If it is, and Heterodontosauridae and Marginocephalia form a clade, then pachies and ceratopsians would all become ornithopods. Looks like another job for Mike... :-)


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