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Re: Some thoughts on AVES



I understand that Mike, but if we put our cleverness thinking caps on, I think we can find an appropriate gap that will be stable even as it does fill in. They did it with mammals a long time ago, and I think we can find a reasonably good equivalent for Aves. Not all transitions are equally gradual, and the faster it happened the better.
Another consideration is trying avoid an enormous expansion of Aves, so Tracy's nomination of the diapsid character will probably not be high on my list. I think it would be best to keep crocs in Reptilia.
So hopefully we can find an appropriate gap and character transformation which would only transfer a subset of dinosaurs to Aves. Theropoda would probably be on my short list, especially if Phytodinosauria should prove to be holophyletic.
I have no problem bucking the Archaeopteryx tradition, but the further back we move the line, the harder it will be to get it accepted. My best guess is that it will involve a subset of Theropoda rather than the whole group, but not excluding the possibility a subset of dinosaurs more inclusive than Theropoda. It's too soon to know how things will turn out.
-------Ken
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T. Mike Keesey wrote:
Ken, don't you see that any "larger gap" you choose is just going to fill
in as we make new discoveries? Evolution occurs through the accumulation
of minute changes, not the sudden appearance of radical changes. If you
try to pick a character you're just going to find that it arose gradually
and that there will be forms where it is debatable whether it has the full
character or not.

This is incredibly UNstable, because it decides ranks based on where the
largest gaps in our knowledge currently are, something which changes as
new discoveries are made.

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