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Re: Defining Ornithischia (was Re:)

David Marjanovic (david.marjanovic@gmx.at) wrote:

<Philosophical arguments have been made about this point (before phylogenetic 
nomenclature came along, at least). One suggestion was to regard secondary 
absence as a special kind of presence, so that snakes can still be regarded as
tetrapods... >

  Doesn't something odd happen to you when you read a cladogram or a
synapomorphy support list in one study and start looking at the acquisition and
loss of features and think, "Hmm, this animal lost a feature..." Maybe one is
thinking, losing a feature is not as big as gaining one, right?

  The loss of a feature in a cladogram is the same as acquiring one, even if
it's a reversal from an earlier trend. So as David may have a pet peeve about
people using "Phylogenetic taxonomy" as I did earlier, this peeves me when
people mention something about how it's awesomely spectactular that a taxon or
grade loses a feature, as opposed to acquiring one (which they are assumed to
have done). The dichotomy being, there is no real dichotomy, and a reversal is
the same as an acquisition, but it effects long-branch attraction differently.


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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