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Re: Tetanurae

Mickey Mortimer wrote:

As an aside, I don't agree with Sereno's revision of Tetanurae's definition, adding Carnotaurus. As I wrote previously-The addition of Carnotaurus as an external specifier by Sereno (2005) seems counter-productive. Tetanurae was designed as a stem away from Ceratosaurus, and abelisaurids were not explicitly discussed (having been named only a year prior). In fact, technically, Indosaurus and Indosuchus were classified as tetanurines by Gauthier (1986), since he lists them as carnosaurs. If abelisaurids are megalosauroids (as in Paul, 1988), it shouldn't stop megalosauroids from being tetanurines.

I disagree. I think adding an abelisauroid as an external specifier is a great idea. Sereno added _Carnotaurus_" to ensure the stability of the taxonomic content of the Tetanurae". The revised definition succeeds on this point, and is much better in this respect than having only _Ceratosaurus_ as the external specifier.

Although Gauthier (1986) was the guy who erected Tetanurae (and resurrected Ceratosauria), abelisaurids (collectively or individually) had not yet been exposed to a cladistic analysis. _Indosaurus_ and _Indosuchus_ might have been classified as tetanurans by Gauthier, but he also treated tyrannosaurids as carnosaurs. These were all a priori assumptions made by Gauthier, and not actually tested.

Paul's (1988) classification of theropods was not cladistic. But if, for example, a cladistic analysis does recover abelisauroids as the sister taxon to carcharodontosaurids (as has come up), then Tetanurae would certainly contract (and would probably be equivalent in content to Neotetanurae!). So much for "taxonomic stability". But I would regard an abelisaurid+carcharodontosaurid clade as a remote (but exciting) possibility.



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