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Clade nomenclature Re: Ceratosauria vs. Neotheropoda?



Combined answer to stuff written by several people, whom I can't cite easily because I can't find any such setting in Thunderbird.

(Hmmmm. Are there native speakers who would use "stuff" and "whom" in the same sentence?)

 I think you might be overstating the importance of "original meaning"
 in framing definitions and converting time-honored groups to clades.
 There's no rule that says you *must* adhere to the original meaning
 of a name when converting it into a clade name.

Indeed not. Instead, there's a rule (Art. 10.1) that requires "minimiz[ing] disruption of current and/or historical usage":
http://www.ohio.edu/phylocode/art10.html

The original meaning is not always the same as the one that has been most common. As an extremely simple example, Lissamphibia Haeckel 1866 explicitly excluded the caecilians (part of the paraphyletic Phractamphibia Haeckel 1866) in the original publication, but the next paper to use that name (a few years later by someone else) included them, and so have all publications ever since. Art. 10.1 clearly argues against restricting Lissamphibia to frogs + salamanders (a clade nowadays called Batrachia... a name with a very complex history behind it) and for using it for the crown-group of extant amphibians, if these form a clade to the exclusion of us amniotes.

 Personally, I would prefer that Ornithosuchia be defined such that it
 includes _Ornithosuchus_ - for the sole reason that the name was
 erected specifically to include _Ornithosuchus_.

Mike Keesey has already explained Art. 11.7:
http://www.ohio.edu/phylocode/art11.html

 Similarly, Pseudosuchia was erected specifically to *exclude*
 crocodiles (hence the name).  Yet some definitions of Pseudosuchia
 allow the crocodilian-containing clade Suchia to be a subset of
 Pseudosuchia, which strikes me as ridiculous.

There are several more such cases, like Paracrocodylomorpha which is meant to include Crocodylomorpha, and the fortunately forgotten Eotetrapoda which was meant to include all limbed vertebrates (Tetrapoda being limited to the crown-group in that scheme). Rec. 11G (more precisely Note 11G.1) is against that:
http://www.ohio.edu/phylocode/art11.html (bottom of the page)

 Caveat author!

Auctor, actually. Connected to "augment" and "Augustus". The overzealous Renaissance etymologists who meddled with the mediaeval spelling _autor_ (which is preserved in many languages today) were right that it wasn't classical, but, well, wrong about everything else, even the language it's from (Latin, not Greek as the _th_ requires).

 However, sometimes compromises have to be made: Dinosauria now
 includes birds (Aves), even though this would make Richard Owen spin
 in his grave.  But the nesting of birds inside Dinosauria is a
 phylogenetic reality, and so overrides historical usage.  Ditto for
 nesting tetrapods inside Osteichthyes, or putting mammals inside
 Therapsida.

However, the PhyloCode nonetheless recommends against making it so by definition, and even uses Dinosauria as Example 1 (of Rec. 11F) on selecting internal specifiers from among the originally included taxa. Science, not nomenclature, should be how we know that birds are dinosaurs.
http://www.ohio.edu/phylocode/art11.html

(Also, if it hasn't become too boring, Owen is continually rotating anyway because nobody listens to his peculiar brand of creationism anymore. But I digress.)

I do dislike the name Osteichthyes, but the alternatives proposed so far -- Euteleostomi, Neoteleostomi, Osteognathostomata -- all have drawbacks of their own...

 In situations like this, the only options are to expand the
 understanding of the taxon (as with Dinosauria, now
 all-but-universally understood to include birds), or to draw back and
 not assign a clade definition of the name at all (which, happily,
 sees to be the way we're headed with the paraphyletic group
 Reptilia).

I fear it's not a done deal, though. I'm not quite sure what for instance Robert R. Reisz, whose middle R is said to stand for "Reptile", is contributing to the Companion Volume...

 Now, in the case we had some original meaning of Ceratosauria
 including Ceratosaurus and ornithomimids, but excluding Allosaurus
 (and if we want to follow original meaning instead of common usage)
 we may do what Mike said and make a [node-based] definition with
 internal specifiers Ceratosaurus and Ornithomimus and external
 specifier Allosaurus, and then make the name get destructed at
 paraphyly/polyphyly.

But we don't want that. We want to keep the name Ceratosauria for the clade for which it has been constantly used in the last few decades. For that, a branch-based definition like "everything closer to *Ceratosaurus nasicornis* than to *Allosaurus fragilis*" would probably be best.

 Note that you *can*, however, define "Archosauria" without
 Archosaurus rossicus, because Archosauria is not named after
 Archosaurus. (Archosauria was named much earlier.)

Apparently *Archosaurus* was named after Archosauria in both senses of "after" -- it is the oldest known archosaur and was probably thought to be a direct ancestor of all others, thus, in a sense, "the" archosaur (such as the only archosaur of its Permian time).

 > Similarly, Pseudosuchia was erected specifically to *exclude*
 > crocodiles (hence the name).  Yet some definitions of
 > Pseudosuchia allow the crocodilian-containing clade Suchia to be
 > a subset of Pseudosuchia, which strikes me as ridiculous.

 Me too. Under the PhyloCode this will likely be "Pan-Crocodylia" (or
 at least, informally, "pan-Crocodylia").

What about Crurotarsi?