Re: FW: Dracorex's phylogenetic position examined with science

[Nick <nick.gardner@gmail.com>]

On 6/22/06, Jaime A. Headden wrote:
>   Lastly, one might attempt to merge the disparate matrices of Williamson and
> Carr and that of Sullivan, as this might best capture their different coding
> perceptions and give where each analysis differs in characters an attempt to
> fill in some blanks. That Williamson and Carr started from scratch, and
> Sullivan from a root Sereno, 1999 cladogram, though Sullivan adds characters,
> might best be treated as a cohesive treatment all taxa might be coded into.

I'd like to clear up the misconception, Sullivan derived his character
list first from Sereno (2000- not 1999, though they're nearly
identical IIRC), as does Williamson and Carr's. Both authors went on
to add additional characters and made changes to Sereno's existing
ones.

On 6/23/06, Michael Mortimer wrote:
> Well, Bakker lacks a pachycephalosaur matrix (as I'm sure he always will).
> Sullivan's (2003) is based on Sereno's, with several characters added.  From
> prior experience, I know Sereno's analyses tend to exclude conflicting data,
> giving them very high Consistancy Indices (Sullivan's variant of Sereno's
> is .91 compared to Williamson and Carr's .83).
>  So not only did I feel
> Williamson and Carr's would be less biased, but I felt it would have the
> greatest chance of changing to a novel phylogeny (as advocated by
> Sullivan) given the data added by Dracorex.

I agree with this, however, I went on to do the following:

> It would be interesting to
>  code Dracorex in Sullivan's matrix

Strict consensus of 6 MPTs, 57 steps-
--+--Ornithopoda
 |--Ceratopsidae
 `--+--Stenopelix
    `--+--Wannanosaurus
       `--+--Goyocephale
          `--+--Homalocephale
             |--Stegoceras
             `--+--+--Tylocephale
                |  |--P. prenes
                |  `--+--P. goodwini
                |     `--+--P. brevis
                |        `--P. edmontonensis
                `--+--+--Colepiocephale
                   |  `--Hanssuesia
                   `--+--Dracorex
                      |--Pachycephalosaurus
                      `--Stygimoloch

Sullivan (2003) had 3 MPTs with 54 steps, and the same topology
excluding the presence of Dracorex. It doesn't seem that the inclusion
of Dracorex in either matrix makes "previous phylogenetic analyses ...
inadequate".

> , just as it would be interesting to
> merge the two matrices.

Perhaps.

Nick Gardner

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