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Re: Lumping Spinosauridae Redux



--- "Jaime A. Headden" <qilongia@yahoo.com> wrote:

> [For those of you on the PhyloCode list, this stems from a discussion on
> synonymy of *Baryonyx* and *Suchomimus*, and how you can prove this
> scientifically. Appologies for cross-posting, but this contains material
> relevant to both lists.]
> 
> Mike Taylor (mike@indexdata.com) wrote:
> 
> <To be clear, I fully realise that you are not advocating going to these
> extremes.>
> 
>   ... quite the opposite, in fact, Mickey likes genera :) ...
> 
> <But I do think this shows that you can't just rely on monophyly of the
> new, broader genus when deciding whether one should be sunk into another.>
> 
>   I have a different position, one of first assignment with given
> priority. If, in the course of a taxon's assignment, a species is coined
> and assigned to a genus, it pertains to that genus from thenceforth. IF,
> however, a species is separated from a genus and established in its own
> right, it should be determined to belong to this new genus. Thus
> preserving historical artifacts. However, if a species is referred to
> another genus, one which is NOT new, and the species had its own unique
> container (a genus) separate from this new referral, it should remain in
> its own container, unless the species too is also a synonym.
> 
>   Example:
> 
>   *Aublysodon molnari* was originally designated, until at some point, it
> was recognized that *Aublysodon* was not the "correct" container for
> *molnari*; *A. molnari* was assigned a new container, *Stygivenator
> molnari,* at which point this referral business ends. However, if
> *molnari* belongs to either *libratus,* *sarcophagus,* *torosus,* *rex,*
> or potentially even *bataar,* we should lose *Stygivenator* in referral of
> *molnari* to one of those species as a juvenile form. The only way we lose
> *Stygivenator* is with loss of *molnari* as a junior objective synonym.
> 
>   Hence, until one can prove that *walkeri* is a senior synonym of
> *tenerensis,* the separation of *Baryonyx* and *Suchomimus* is just as
> valid. They currently contain equivalent taxa, from the "species" to the
> "genus," which Mickey himself has yet to determine _how_ these are to be
> differentiated, only treated them as if they were distinct entities. This
> is my idea as it stands.

In fact, my provisional treatment of genera works out much the same way. I
define each genus as a stem-based clade with the type species as the internal
specifier and every type species of every other genus as external specifiers.
Thus:
_Suchomimus_ = clade(_terenesis_ not [all other type species]}

Thus, _Suchomimus_ is only invalidated under two circumstances:
1) If _tenerensis_ is synonymous with a species which is the type of an older
genus, in which case _Suchomimus_ becomes a junior synonym of that genus.
2) If _tenerensis_ is ancestral to some other type species, in which case
_Suchomimus_ becomes a null clade.

The only difference with Jaime's system is that my system allows for non-type
species to not have any genus. For example, if _sternbergi_ is the type species
of _Pentaceratops_, _belli_ is the type species of _Chasmosaurus_, and
_Chasmosaurus irvinensis_ turns out to fall right outside clade(_belli_ and
_sternbergi_), then _irvinensis_ cannot be assigned to any genus. It is instead
referred to by the least inclusive clade which it does belong to, e.g.,
_Chasmosaurinae irvinensis_.

Of  course, I don't think either of these systems will be good in the long run.
I'll only use mine until something better comes along.

>   One consideration (Mike Keesey has advocated this in part for the sake
> of defining "genera") is that everything above the "traditional"
> species-level taxaon is not a named type of clade, but just a clade,
> including "genus." In this manner, Clade={*Suchomimus*} is inclusive of
> only *tenerensis,* and all other designated type species are not (this
> would have to have another temporal modifier).

Temporal modifier?

> By using the same formula,
> *Baryonyx* can never include *tenerensis,* even if they were found to be
> synonymous, because their definitions would mutually prohibit it. I don't
> like this solution.

Not so. If _tenerensis_ and _walkeri_ are the same, then _Suchomimus_ and
_Baryonyx_ are heterodefinitional synonyms (see above).


=====
=====> T. Michael Keesey <http://dino.lm.com/contact>
=====> The Dinosauricon <http://dinosauricon.com>
=====> Instant Messenger <Ric Blayze>
=====


                
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