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Re: Ceratosauria vs. Neotheropoda?

On Sat, Nov 21, 2009 at 5:14 PM, Tim Williams <tijawi@yahoo.com> wrote:
> I think you might be overstating the importance of "original meaning" in 
> framing definitions and converting time-honored groups to clades. ÂThere's no 
> rule that says you *must* adhere to the original meaning of a name when 
> converting it into a clade name.
> For example, the name Ornithosuchia was originally erected by Huene to 
> include _Ornithosuchus_ (he erected Ornithosuchidae at the same time). Â
> However, since then Ornithosuchia has been used for a much larger archosaur 
> clade, and some definitions (e.g., "the most inclusive clade Aves but not 
> Crocodylia") would actually result in clade Ornithosuchia excluding 
> _Ornithosuchus_.
> 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_.

Although adhering to "original intent" is of course only something
that can, in most cases, only be a recommendation, the PhyloCode does
have an actual *rule* about eponymy. You *cannot* define
"Ornithosuchia" without making Ornithosuchus longidens an internal
specifier. You also *cannot* define "Ceratosauria" without
Ceratosaurus nasicornis as an internal specifier. (See Article 11.7.)

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

The total clade called "Ornithosuchia" (or "Avemetatarsalia") will
probably be named "Pan-Aves" under the PhyloCode, in keeping with the
panclade name convention for names of total clades. However, one of
those other names could be selected, in which case "pan-Aves" would be
available as an informal alternative.

> Similarly, Pseudosuchia was erected specifically to *exclude* crocodiles 
> (hence the name). ÂYet 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").
T. Michael Keesey
Technical Consultant and Developer, Internet Technologies
Glendale, California