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Re: MULTIPLE INCLUSIVE ANCHORS?



On Wed, 13 Feb 2002 Tetanurae@aol.com wrote:

> Mike Keesey wrote, quoting Gauthier and de Quieroz:
> <<Galloanserae_ = Clade(_Phasianus [Gallus] gallus_ + _Anas [Anser] anser_)
> ("Pangalloanserae" suggested for Clade(_Phasianus gallus_, _Anas anser_
> <-- _Fringilla domestica_).)>>
>
> Plus many other
>  stem based taxa with more than one inclusive anchor.  I thought that this
> could not be possible, because a topology like this [which is technically
> possible, we don't have the hindsight of the creator of the universe]:
>
> --+--Gallus
>   `--+--Anser
>      `--Fringilla
>
> would indicate that this supposed stem based clade  is actually composed of
> two different stems that are serial outgroups to Fringilla, and polyphyletic.
>
> Am I missing something here?

In this case, the definition falls apart, and _Galloanserae_ does not
refer to any clade. The draft PhyloCode allows this:

"11.9 ...
Example 3: If a name is defined through a stem-based definition with more
than one internal specifier, and one internal specifier is later found to
be more closely related to the external specifier than to the other
internal specifier, the definition does not apply to any clade...."

So that definitions is okay (insofar as PhyloCode is concerned). But I
took another look at this style of definition, which they use in several
places:

"the crown clade stemming from the last common ancestor of A and all
extant organisms sharing a more recent common ancestor with A then with B"
(Essentially, taking a stem-based clade and making a node-based clade
using its extant members.)

This seems to be invalid under the draft PhyloCode, which states:
"11.3. When a species is used as a specifier, the author and publication
year of the species name must be cited."

Here they only cite the author and publication year of species A (and
species B, but that's not really a specifier of the clade in question),
but not of any of the other specifiers, instead providing a formula for
determining them. Interesting idea, but I don't think it's allowed, at
least under this draft.
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