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Re: *Gansus*



>What chance is there that *Gansus* actually belongs into Hesperornithes?

>As explained in their supplementary information, You et al. (2006) found 24 
>MPTs, in which *G.* was either outside of (Hesperornithes + Neornithes) or 
>closer to Neornithes than *Ichthyornis* or (as in the majority-rule consensus 
>tree in the paper itself) closer to (Neornithes + *Ichthyornis*) than to 
>Hesperornithes.

>Neither *Enaliornis* nor *Pasquiaornis* (nor, unsurprisingly, *Potamornis*) 
>were included; the only representatives of Hesperornithes are *Baptornis* and 
>*Hesperornis*. The supp. inf. states that *E.* was excluded because it shows 
>hesperornithean autapomorphies and would therefore predictably have come out 
>as >the sister-group to *Baptornis* + *Hesperornis* -- but I can't see why 
>that's an argument. It would after all have broken up the very long branch 
>that leads to (*B.* + *H.*); I wonder if we are seeing long-branch attraction 
>of (*B.* + *H.*). away from *G.*. The occurrence of MPTs where *G.* is outside 
>(Hesperornithes + Neornithes) shows that the phylogenetic position of (*B.* + 
>*H.*) is unstable.

    I think I can interject here (from being on vacation)...
 
    We simply used Clarke & Norell's matrix, with a few changes and additions 
-- we didn't try to change or add codings from anything we hadn't personally 
seen (well, Luis & Jingmai probably saw, and they did contribute to our changes 
for a few things), including _Enaliornis_.  This wasn't because we were/are 
lazy -- we are trying hard to get the funding we'll need to go see as many of 
these things in person as humanly possible -- but because our analysis was 
preliminary.  Like a lot of these kinds of phylogenetic analyses, we depended 
on other people's codings to be accurate and simply added our stuff to get a 
preliminary estimate of where _Gansus_ lay.  We had kind of predicted it would 
be fairly derived, based on its various characters, but were pretty surprised 
that it came out as advanced as it did -- that was the thing that made it 
_Science_-worthy.  If/when we get our funding, we will do a much more detailed, 
monographic osteology and comparison with lots of other things, and
 hopefully all will made much clearer, including whether or not _Gansus_ really 
is where we found it the first time (and yes, we have contemplated that it's a 
basal hesperornithean, specifically one that was still volant).  Rest assured 
also that a brand-new data matrix is being compiled, based in part on Clarke & 
Norell and others but with lots of new/changed characters and more accurate 
codings.
 
    We are aware of the various problems that convergence, long-branch 
attraction, etc. can have on an analysis with a taxon like _Gansus_; we're 
keeping all this in mind.  Still, it does beggar the question of exactly how 
much faith one can put in a computer-generated analysis when the human mind 
says something else...are we Borg or are we capable of abstracting beyond a 
bunch of statistics?  (Not an argument I'm going to have here...)
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
 and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/
 
"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and
humans is like trying to decipher
Demotic Egyptian with the help of an
odometer and the Oxford English
Dictionary."
               -- D. Graur & W. Martin
                    (_Trends in Genetics_
                    20[2], 2004)