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

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 ...

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


Nick Gardner

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