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

[Stanley Friesen <sarima@friesen.net>]

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.

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