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Re: The Papers That Ate Cincinnati
Mike Keesey wrote:
It depends on the definition. (And it's not a matter of classification, but
of changing phylogenetic hypotheses.) If a clade is defined with
_Opisthocomus hoazin_ as a specifier, then that species shifting around in
different cladograms may affect our understanding of the clade's content.
But I don't think anyone's ever used _O. hoazin_ as a specifier for any
clade, and, given its uncertain position, I'm not sure anyone would want
to. (Except in case the genus _Opisthocomus_ or any eponymous taxon is
converted as a clade name, of course.)
A stem clade "Panopisthocomiformes" could be erected for all birds closer to
the hoatzin (_Opisthocomus hoazin_) than to any other modern bird. It might
include such fossil taxa as _Hoazinoides_ and _Foro (if not a
musophagiform), though probably not the highly dubious _Onychopteryx_.
Given the highly uncertain relationships of the hoatzin, a node-based or
stem-based definition of Opisthocomiformes would be highly problematic. I
don't see any easy solution, except by resorting to a long list of external
specifiers. The alternative is to make Opisthocomiformes apomorphy-based,
as Clarke et al. (2003) suggested for Sphenisciformes.
Evelyn Sobielski wrote:
Then, anything that is unicellular and reproduces clonally. In these cases,
ontogenetic genetic changes (eg by HGT) *are* possible phylogenetic
changes. Howto define clades in these?
Or try Woese
These days, higher-level classification of prokaryotes (bacteria and
archaea) is based on 16S phylogeny.
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