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Re: D.Marjanovics repliesto J'r pts I-II
David Marjanovic wrote-
> There are a few papers whose authors have looked at every specimen
> they've coded. HP Oliver Rauhut's dissertation and follow-up paper are
Not true. Rauhut didn't personally examine Euparkeria, Staurikosaurus,
Herrerasaurus, "Szechuanoraptor", Poekilopleuron, Torvosaurus,
Monolophosaurus, Siamotyrannus, Sinraptoridae or Bagaraatan.
Peters is correct. It's simply not feasible to see every specimen, and
people do write articles in the literature for a reason. If we're not going
to code off those, why should they bother writing? They could just say
"yeah, our specimen is new, come to this museum and look for yourselves if
you want to know anything about it." Knowing what we do about the
importance of including all specimens with unique character combinations,
it's probably less detrimental to code a specimen incompletely from the
literature than to exclude it from the analysis. And even if you code off
someone else's matrix, your data is at least as correct as theirs, and their
article was apparently fit to publish.
Note I do think seeing taxa, or at least multiple good photos, in person is
important. The literature has enough errors and misinterpretations possible
to make that obvious. I just think it's ridiculously idealistic to think
data isn't publishable until all specimens are personally examined.
> Your... idealism is breathtaking.
> Yes, Nature is a single tree, so we should ideally get a single tree if we
> look for shortest -- or most likely! -- trees. But to get that tree, we
> would need all nature in our matrix. Not only would we need from 1000
> characters upwards for a pterosaur matrix.* What proportion of _all
> pterosaur species that have existed_ do you think there are in your
> 1 %? 0.1 %? With samples this small, the chance is high that we introduce
> huge artifacts. Remember how Mickey always reports on what happens when he
> adds one more coelurosaur to his matrix.
> In short, we _are_ unable to finish the job in the foreseeable
> future. Period.
I think Peters has a point here too. With the small amount of characters
and taxa in nearly any dinosaur or pterosaur cladogram, the authors
certainly haven't tried hard to "finish the job". Holtz (2000) is the one
near exception among coelurosaur cladograms. My analysis may have >400
characters, but I haven't even begun to try "finishing the job". It may not
be possible to get a confidently true tree from our small sample sizes, but
it's usually possible to get a well resolved tree, ignoring instances where
related taxa preserve no elements in common.
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html