[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: tiny-armed theropods





----------------------------------------
> Date: Mon, 17 Oct 2011 18:41:41 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: tiny-armed theropods
>
> Anthony Docimo <keenir@hotmail.com> wrote:
>
>
> > On the other hand, if you make up a name that you think all Coelophysids 
> > and Podokesaurids can be grouped together within (say,
> > Gdayraptoroidea), that might also prove labile if the features you assign 
> > it (based on the Coelophysids and Podokesaurids and anyone
> > else you group with them at the time) turn out to be not what you 
> > thought...such as if _Coelophysis_ belongs outside the group, far away
> > from _Podokesaurus_.
> >
> > Would the Gdayraptoroidea have to be scrapped?
>
>
> I might not be fully understanding you here, 
 
 from what I see below, you appear to understand - if you're not understanding, 
it's non-understanding on a level over my head anyway.  :-)
 
 
> (1) Coelophysoidea is tied to _Coelophysis_. Podokesauroidea is tied
> to _Podokesaurus_. If _Podokesaurus_ is not a member of the clade
> Coelophysoidea (defined as _Coelophysis_ but not _Ceratosaurus_,
> _Carnotaurus_ or _Passer_), then there is no problem. But if
> _Podokesaurus_ is inside Coelophysoidea then the ICZN would say we

> have to re-name this clade Podokesauroidea. I say this is silly,
> because Podokesauroidea has no phylogenetic definition - and we
> shouldn't have to provide it with one just for this contingency.
 
 Wouldn't it be better to have a definition ready for use, *before* such a 
contingency need arises?
 
 
> (2) Those "features you assign to it" constitute the diagnosis, not a
> definition. Unless you're advocating an apomorphy-based definition of
> Gdayraptoridae (and I don't think you are), the definition of
> Gdayraptoridae would be linked to specific taxa, such as _Coelophysis_
> and/or _Podokesaurus_. Thus, the content of Gdayraptoridae would
> depend upon how you define this clade. For example, if you were to
> define Gdayraptoridae as "all descendents of the most recent common
> ancestor of _Coelophysis_ and/or _Podokesaurus_" then the content of
> Gdayraptoroidea would depend upon the relative position of
> _Coelophysis_ and/or _Podokesaurus_ within a cladogram.
 
 So if, as I suggested, _Coelophysis_ turned out to be farther away 
relationship-wise from _Podokesaurus_ than previously thought, then 
Gdayraptoridae would simply expand...it wouldn't be rendered moot and useless.
 
 
> (3) Because there is currently no genus Gdayraptor or family
> Gdayraptoridae, the group Gdayraptoroidea is NOT a coordinated
> family-level taxon. Thus, Gdayraptoridae does not fall under ICZN
> rules. Coelophysoidea and Podokesauroidea, on the other had, do.
 
 That was kinda my point about _Dinosauria_ itself in a recent post.  :-)