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Re: Ceratosauria vs. Neotheropoda?

In Sereno's defense, he realized the error of his ways in framing a definition 
of Ceratosauria that included _Coelophysis_ (but not _Ceratosaurus_) as an 
internal specifier.  Thus, he later (2005) coined a new definition that 
replaced _Coelophysis_ with _Ceratosaurus_.  This was a good move (although 
belated), because it meant that _Ceratosaurus_ is guaranteed to be a member of 
the clade that takes its name, irrespective of _Ceratosaurus_'s phylogenetic 
position relative to other theropods.

However long before this point, Holtz and Padian (1995) had erected a 
stem-based definition for the clade Ceratosauria ("All theropods closer to 
_Ceratosaurus_ than to birds").  This definition was essentially retained by 
Sereno (2005) ("_Ceratosaurus nasicornis_ but not _Passer domesticus_").  
Personally, I think this definition is fine, although I agree that it can't 
hurt to include _Allosaurus fragilis_ as an external specifier. 

At one stage, Marsh (1895) included ornithomimids in the Ceratosauria.



--- On Fri, 11/20/09, Augusto Haro <augustoharo@gmail.com> wrote:

> From: Augusto Haro <augustoharo@gmail.com>
> Subject: Ceratosauria vs. Neotheropoda?
> To: "Dinosaur Mailing List" <dinosaur@usc.edu>
> Date: Friday, November 20, 2009, 4:59 PM
> Question for people who know about
> Phylocode:
> Langer et al. (2009) pointed out that the oldest available
> phylogenetic definition of Ceratosauria is synonymous with
> Neotheropoda. They point out that Rowe and Gauthier (1990)
> defined
> Ceratosauria as a node-based taxon this way: "We employ the
> name
> Ceratosauria for the group including Ceratosaurus
> nasicornis,
> Dilophosaurus wetherilli, Liliensternus liliensterni,
> Coelophysis
> bauri, Syntarsus rhodesiensis, Syntarsus kayentakatae,
> Segisaurus
> halli, Sarcosaurus woodi , and all other taxa stemming from
> their most
> recent common ancestor".
> Sereno (1998) defined Neotheropoda this way: "Coelophysis,
> Neornithes,
> their most recent common ancestor and all descendants", and
> later
> (2005), this way: "The least inclusive clade containing
> Coelophysis
> bauri (Cope 1889) and Passer domesticus (Linnaeus 1758)."
> Accepting the phylogenetic hypothesis of Rauhut (2003),
> that what
> Gauthier called Ceratosauria is not monophyletic, with
> Ceratosaurus
> being closer to Tetanurae than to Coelophysis, it seems
> that both
> definitions group the same taxa, as expressed in Langer et
> al (2009).
> Is there a reason for not using Ceratosauria instead of
> Neotheropoda?
> The definition by Rowe and Gauthier (1990) seems like
> acceptably
> constructed from the comments.