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Re: birds and/or/with dino's

On Wed, Sep 16, 2009 at 5:25 PM, Tim Williams <tijawi@yahoo.com> wrote:
> Yet, we already do link many clade definitions with phylogenetic hypotheses. Â
> For example, Saurischia is used for the dinosaur clade that includes 
> Theropoda and Sauropodomorpha, but not Ornithischia. ÂFollowing Sereno 
> (2005), the clade Saurischia is defined such that it can only be used for the 
> Theropoda+Sauropodomorpha clade. ÂThus, clade Saurischia is explicitly tied 
> to the phylogenetic hypothesis that Theropoda and Sauropodomorpha are closer 
> to each other than either is to the Ornithischia.
> If new fossil discoveries support a clade that includes Sauropodomorpha and 
> Ornithischia but excludes Theropoda, then the clade Saurischia ceases to 
> exist. ÂHowever, the name Phytodinosauria is available for a 
> Sauropodomorpha+Ornithischia clade. ÂPhytodinosauria would *only* be used in 
> the event of a Sauropodomorpha+Ornithischia clade being supported by 
> phylogenetic analysis.
> Thus, Saurischia and Phytodinosauria are each linked to separate phylogenetic 
> hypotheses that are mutually exclusive. ÂFurther, the names reflect the 
> individual phylogenetic hypotheses, based on traits inferred to be primitive 
> for each clade: Saurischia (propubic pelvis) and Phytodinosauria (herbivorous 
> dinosaurs).

It's not necessary to define these in such a way -- the matter can be
resolved using priority instead. Suppose we used these definitions,
listed in order of precedence:

 Dinosauria := Clade(Megalosaurus bucklandii + Iguanodon bernissartensis)
 Theropoda := Clade(Megalosaurus bucklandii <-- Diplodocus longus)
 Saurischia := Clade(Megalosaurus bucklandii <-- Iguanodon bernissartensis)
 Phytodinosauria  := Clade(Iguanodon bernissartensis + Diplodocus longus)

Under the "phytodinosaur" hypothesis, Saurischia would become a
heterodefinitional synonym of Theropoda. Under the more usual view,
Phytodinosauria is a heterodefinitional synonym of Dinosauria.
Precedence removes the unnecessary name in either case.

(That said, I don't have a real problem with using multiple internal
specifiers for Saurischia -- it all amounts to about same thing in the

> Even if polyphyletic, they were also paraphyletic given that they were the 
> putative basal members of much larger groups (Condylarthra-Ungulata; 
> Protozoa-Eukaryota; Proteutheria-Eutheria). ÂOr I may have misunderstood you 
> here (if so, I apologize in advance)...

A polyphyletic taxon cannot also be paraphyletic -- they're mutually
exclusive categories. (And Ungulata is polyphyletic, anyway.) And I
thought Proteutheria was a more specific grouping than an equivalent
of "stem-Eutheria".

Or do you mean that they were considered paraphyletic, even though
they later turned out to be polyphyletic?

>> The rest more or less
>> correspond to clades which already had other names: Insecta
>> (or Hexapoda),
> Apterygota referred to the primitively wingless insects, so it would be 
> inappropriate to expand this group into a clade that includes *all* insects 
> (including the winged ones). ÂSome entomologists have retained Apterygota for 
> the clade of primitively wingless ectognathous insects (such as silverfish) 
> that is the sister taxon to the winged insects (Pterygota), which are also 
> ectognathous.

Right, because the larger clade already has a perfectly good name.

>> Something like this could work:
>> Artiodactyla := Clade(Sus scrofa + Camelus dromedarius +
>> Bos taurus)
>> Cetartiodactyla := Clade(Balaena mysticetus + Sus scrofa +
>> Camelus
>> dromedarius + Bos taurus)
> Yep, agreed. ÂIn your scheme, both Cetacea and Artiodactyla are restricted to 
> their respective crown groups, which is a neat idea.

I like it, but we'll see how it actually pans out....

>ÂOther available names could be used for the respective stem groups: Cete 
>(stem-Cetacea; which would include the raoelliids under Thewissen &c's 
>phylogeny) and Paraxonia (stem-Artiodactyla).

You mean total groups, no? (Stem-Cetacea roughly corresponds to
Archaeoceti.) Interesting idea.

Note that the PhyloCode would allow the coexistence of these as total
group names along with the informal names "pan-Cetacea" and

>> Then give the former precedence if they turn out to be
>> heterodefinitional synonyms. (Mmm, cinnamon.)
> Thanks - now I have a donut craving....

Homerdefinitional cinnamons!

T. Michael Keesey
Technical Consultant and Developer, Internet Technologies
Glendale, California