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Re: Non-serpentine lacertids (was RE:WHAT'S GOING ON?)



At 03:34 PM 7/3/00 -0400, T. Mike Keesey wrote:

Because removing Aves from Dinosauria precludes other distinctions. It
says "this distinction is more importent than other distinctions along the
lineage".

Yes.

 Why should it be cut at Aves? Why are the distinctions between
_Archaeopteryx_ and basal Eumaniraptora more important than the
distinctions between basal Maniraptoriformes and basal Coelurosauria?

This is where information theory is used in a proper non-cladistic system. That cut is used which maximizes information content. The distinction is more important because it summarizes more information than the others.


This is what Dr. Ashlock's system was trying to accomplish.

Now, in actual fact the proper analysis has not yet been performed with regard to Aves versus dinosaurs, so the proper place for the cut is, strictly speaking, not yet known. Indeed, analysis may show it to be inappropriate in this case (though I doubt it). It is quite possible that after analysis the best place for the cut would put the paleornithines in Dinosauria not Aves.

 Or
between basal Ornithodira and basal Archosauria? Or between basal
Neornithes and basal Carinatae?

All of these distinctions are important. Placing more significance on one
than on the others undermines our understanding of evolutionary history.

How? The cladogram is still there to see all of them if one needs to. To my mind pretending all evolutionary changes are *equal* undermines our understanding of certain aspects of evolutionary history - especially evolutionary ecology.


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May the peace of God be with you.         sarima@ix.netcom.com