RE: Kerberosaurus manakini

[Mike Milbocker <mmilbocker@psdllc.com>]

Mickey Mortimer wrote:

>The authors state- "The purpose of the present paper is to establish the
phylogenetic relationships of the new hadrosaurid genus Kerberosaurus, and
not to propose a complete revision of Hadrosaurinae, which would require a
more extended revision of North American specimens. Therefore, we only
retained characters that can be directly observed on the material referred
to as Kerberosaurus manakini at hand, keeping in mind that more exhaustive
studies of hadrosaurid systematics are in preparation (J. J. Head and D. B.
Weishampel, pers. comm.)."
This is NOT a reason to limit character selection to those that can be coded
for your fragmentary taxon.  This only skews the result of the analysis.
Characters not codable for Kerberosaurus might nonetheless affect clades it
belongs to.  WHY don't the authors realize this?<

Are you complaining that the authors should have looked at other
Kerberosaurus specimens to fill in the missing characters or that they
should have retained the characters but assigned them state value
"undetermined". If you view this as a perturbation theory problem, it would
be less parsimonious to destabilize a well characterized phylogeny by
introducing a taxon that is ill-determined. I think the authors took the
only sensible approach with the limited data available. From perturbation
theory, the small perturbation of leaving out the undetermined characters is
preferred to introducing alot of unconstrained varibles into the system -
which is what you do when you code characters as "undetermined" and build a
systematics on this. Perhaps the authors even did this, and found the number
of equally parsimonious trees to be increased by this approach, which would
be consistent with perturbation theory.


>Finally- "Because missing data may influence cladistic analysis in rather
unpredictable ways (Platnick et al., 1991), we also left out taxa known to
be too incomplete, or requiring systematic revision, such as Hadrosaurus
foulkii Leidy, 1858, Kritosaurus navajovius Brown, 1910 (5Anasazisaurus
horneri Hunt and Lucas, 1993 1 Naashibitosaurus ostromi Hunt and Lucas,
1993), Lophorhothon atopus Langston, 1960, Claosaurus agilis (Marsh, 1872),
Secernosaurus koerneri Brett-Surman, 1979, Aralosaurus tuberiferus
Rozhdestvensky, 1968, or Shantungosaurus giganteus Hu, 1973."
WHEN will people learn poorly coded taxa do NOT negatively influence
results?  They _can_, but they can also have definite placements, or their
unique character combinations can suggest better results.<

I think you have been romanced by the black box, phylogeny programs do not
cope well with poorly coded taxa, and the authors are quite correct.

>In any case, the analysis of so few characters, obviously designed to have
a
preconceived result (CI = .92), is of little use.  I mean, there are two
(count them- two) discordent codings in the matrix (Maisaura lacks character
7, unlike other hadrosaurines; lambeosaurines and saurolophins both have
character 21).  The Sereno-esque "analyses" must stop!<

Wow, one could say the same for your approach. The problem with orthodox
cladistic coding is that it leaves out the numerous details that cannot be
coded. I agree that including them can introduce subjectivity into the
analysis, but when working with a sparce set of data, which most of
paleontology does, the predictive power of cladistics is dubious as well.
Cladistics is useful for illustrating the relationships among taxa for which
the fewest number of state changes occur between related individuals
averaged over all individuals. But to make the fantastic leap that this is
the only way data can be scientifically analyzed is really just as
subjective.

Michael Milbocker