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RE: Two new dinosaurs in JVP: Arcusaurus and Haya



Amusingly, Tornier (1913)  originally used Plateosauria as an alternative 
  name for Theropoda, which also contained basal sauropodomorphs at the time. 
  Also, note Sereno's "2005" definition is unpublished, online only.  While 
Taxon Search credits all his new definitions to "Sereno, 2005", the paper in 
question has not appeared.

Mickey Mortimer

----------------------------------------
> Date: Wed, 11 May 2011 11:39:37 +1000
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Two new dinosaurs in JVP: Arcusaurus and Haya
>
> Brad McFeeters  wrote:
>
> > Yates, A.M, M.F. Bonnan & J. Neveling, 2011.  A new basal sauropodomorph 
> > dinosaur from the Early Jurassic of South Africa.  Journal of Vertebrate 
> > Paleontology 31: 610-625.
>
>
> Although Yates &c erect a new genus (_Arcosaurus_ - "rainbow lizard"),
> there is no net increase in new genera, because _Ignavusaurus_ is sunk
> into _Massospondylus_. Things don't look for _Gryponyx_ either (and
> so soon after it jumped off the nomen nudum merry-go-round).
>
>
> The only quibble I have with the _Arcusaurus_ paper is the use of the
> name Plateosauria. Clade Plateosauria is defined by Yates &c as
> "_Plateosaurus_ + _Massospondylus_ and all descendants of their most
> recent common ancestor." This definition goes back to Sereno (1998),
> where it was clear that Plateosauria was used for a subset of
> Prosauropoda. However, if prosauropods are paraphyletic, and
> _Plateosaurus_ and _Massospondylus_ do not belong to a clade to the
> exclusion of sauropods, then Plateosauria would also include all
> sauropods! To prevent this from happening, Sereno later (2005)
> amended the definition to include _Saltasaurus as a negative taxon
> qualifier. I think this is a good idea: the negative qualifier
> ensures that Plateosauria cannot be used if _Plateosaurus_ and
> _Massospondylus_ are not more closely related to each other than to
> sauropods
>
>
> Yates &c actually recovers _Massospondylus_ closer to sauropods than
> to _Plateosaurus_. Because there is no negative qualifier in the
> definition, the paper uses Plateosauria for the least inclusive clade
> that includes _Plateosaurus_, _Massospondylus_ and sauropods. This
> goes against the grain of the intent behind the name Plateosauria -
> which is as a clade of non-sauropod sauropodomorphs. I know it is
> handy to have a clade that includes "advanced" prosauropod-grade taxa
> (like _Plateosaurus_ and _Massospondylus_) and sauropods, and which
> therefore excludes the most basal sauropodomorphs. But IMHO it would
> be better to use a different name for this clade, such as Sereno's
> Sauropodiformes (although this is anchored in _Mussaurus_) or a new
> name.
>
>
>
>
> Cheers
>
> Tim