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Linnaean vs. Phylogenetic, again



It seems to me that the phylogenetic system is actually *better* at
denoting paraphyletic groups than the Linnaean system. When a paraphyletic
group is officially recognized in the Linnaean system (e.g. Dinosauria
[non-avian]), it can exclude dozens of other paraphyletic groups from
being officially recognized (e.g. non-neornithean Dinosauria,
non-maniraptoran Dinosauria, non-ceratopsian Dinosauria -- whatever). Even
worse, it can prevent monophyletic groups from being officially
recognized. (Linnaean Reptilia prevents official recognition of Synapsida
and Sauropsida.) "Pisces" is not possible under modern Linnean systems,
but "non-tetrapod craniate" is available to cladists. (As is the
shorthand, "fish".)

Under phylogenetic taxonomy, all paraphyletic groups (of equal paraphyly)
are equal and can be termed with precision, using the formula non-xxxan
Xxxx for singly paraphyletic groups, non-xxxan, non-xxxan Xxxx for doubly
paraphyletic groups, etc. (Once you start going above this, you might want
to use "basal", or question whether a term for such a group is really
necessary.) Other adjectives might prove useful as well -- "ectothemic
Amniota" is a good equivalent for the traditional concept of Reptilia;
"Mesozoic Dinosauria" comes in handy for me in a number of cases.

Instead of harming the usage of paraphyletic groups, I think the
phylogenetic system actually enables one to discuss them with greater
clarity and flexibility.

_____________________________________________________________________________
T. MICHAEL KEESEY
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