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Re: Pteros might be dinos?!? Oh no ...

Augusto Haro <augustoharo@gmail.com> wrote:

> The Phylocode-experts here may tell me if for phylogenetic definitions
> there is a rule of priority. In the recent paper of Langer
> et al. (2009) it is said that the first to phylogenetically define
> Dinosauria is Novas (1992), and in this work he specifically
> considered this taxon as a specifier of the Dinosauria, and according to
> him, also Gauthier (1986). However, today we accept a definition
> without Herrerasaurus as a specifier, by Padian and May (1993). Why
> is this so?

With the caveat that I'm not a PhyloCode expert (I've just read the thing), 
there are two separate issues in your question:

(1) There is not yet a "rule of priority" for phylogenetic definitions.  
PhyloCode states: "[T]he names and definitions published in the companion 
volume will be the first to be established under the PhyloCode and will have 
priority over subsequently defined names."  The publication of the companion 
volume will coincide with the starting date of PhyloCode.  This has not yet 
happened yet.

(2) Novas actually defined Dinosauria as Herrerasauridae + Saurischia + 
Ornithischia.  My reading of the PhyloCode leads me to believe that only 
species or specimens can be used as specifiers.  

>From another post, Augusto Haro <augustoharo@gmail.com> wrote:

> Regarding the elongation of penultimate manual phalanges, one should
> have care because that elongation also happens in Heterodontosaurus
> (Santa Luca, 1980, fig. 13), which is considered by now one of the
> most basal ornithischians (Butler et al., 2007). It may be a basal
> dinosaur feature.

Yes, I suspect you're right here.  The elongate penultimate phalanges of 
dinosaurs are associated with improved grasping abilities.  This has been tied 
to predation upon small animals.  This might lend support to the interpretation 
of heterodontosaurids as omnivores, which included small prey in their diets.  

If heterodontosaurids are basal ornithischians, it is remarkable that they 
survived at least into the Early Cretaceous.  By this time, the basal members 
of the saurischian clades had long gone (guaibasaurids, herrerasaurids, even 
the coelophysoids).  However, I should add that phylogenetic analyses tend to 
regard _Pisanosaurus_ as the *most* basal ornithischian taxon, and there is no 
evidence of pisanosaurids beyond the Late Triassic.