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RE: Cladistic Idea



The assumption that earlier taxa are more primitive is the only reason your 
idea would be better than analyzing all taxa.  Since there would be no long 
branches, we wouldn't have to worry about long branch attraction.  I thought 
that was the implied reasoning- to get past the confounding effects of more 
derived taxa on the topology.

Mickey Mortimer

----------------------------------------
> Date: Fri, 15 Jul 2011 18:34:43 -0300
> From: gahrdng@mta.ca
> To: dinosaur@usc.edu
> Subject: Re: Cladistic Idea
>
> Thanks for your explanations, everybody. I understand now: with the fossil
> record as incomplete as it is, we need to use all the information we have.
>
> I do want to argue one point, however. David Marjanovic wrote:
> <<Naturally, it gets worse if the fossil record is worse and D through J 
> isn't a
> clade that exclude A, B and C.>>
>
> And Jason Brougham wrote:
> <<We should
> never conclude from this that opossums are more advanced than mastodons.
> Nor that painted turtles evolved into snapping turtles.>>
>
> But surely my idea doesn't rest on the assumption that the earlier taxa are 
> also
> the most primitive, and that the later taxa all nest together to the exclusion
> of the earlier ones. There's nothing to stop my hypothetical series of
> constrained trees from coming out with a topology like this:
>
> +--F
> `--+--+--I
> | `--+--A
> | `--D
> `--+--+--B
> | `--+--E
> | `--H
> `--+--J
> `--+--C
> `--G
>
> Is there?
>
> -Grant