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Re: Defining Ornithischia (was Re:)



<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...>

Just for the record: I do not wish to imply that I _supported_ that notion. In fact, I regard it as ridiculous and entirely useless, if not outright counterproductive -- I regard it as yet another case of philosophers meddling with science instead of staying at their own affairs. More precisely, the philosopher in question overlooked the tree for the leaves...


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?

I'm not thinking that.

(I could think that, or for that matter its opposite, if the developmentary genetics _and_ the selection pressures on the character in question were all completely worked out. I don't know of a single such case.)