Kerberosaurus paper comments

[Nick Gardner <pyroraptor86@yahoo.com>]

--- On June 16, 2004 Mickey Mortimer wrote:
"I'll leave it to Nick to comment on the taxon itself,
supposedly just outside the Prosaurolophus +
Saurolophus clade.  But I have a few complaints about
the phylogenetic analysis"

I'm sorry for taking so horribly long to reply. I
largely agree with Mickey's comments on the
phylogenetic analysis, however, I have a few more
detailed comments to make, mostly on the characters
used to diagnose the Lambeosaurinae.  I'm not sure why
I'm supposed to comment especially on this, since I
completely lack useful references for the
Hadrosaurinae (excluding this paper and The
Dinosauria), and my entire knowledge of the
Hadrosauridae is limited entirely to the
lambeosaurines and a few basal members.  I am aware
there are certain individuals on this list (hint hint)
who have other opinions as to the phylogenetic
placement of this taxon and I'd like to see them post
something on it.

First, the holotype is not as fragmentary as was
implied on list earlier.  The holotype (AENM 1/319)
consists of portions of the back of the skull,
including the prootic, laterosphenoid, orbitosphenoid,
basioccipital, basisphenoid, parasphenoid, and
parietal. Of these, only the basisphenoid is complete.
The rest are not horribly incomplete, just not as well
preserved and missing parts, it seems.  The referred
material consists of nearly complete paired
exoccipitals-opisthotics (AENM 1/321), frontals (AENM
1/30; AENM 1/31; AENM 1/32; AENM 1/222), paired
prefrontals (AENM 1/243; AENM 1/320), incomplete
nasals (AENM 1/318; AENM 1/324), a nearly perfectly
preserved jugal (AENM 1/200), paired maxillae (AENM
1/322; AENM 1/323), a squamosal (AENM 1/36), and a
quadrate (AENM 1/38).

Now onto those pesky diagnostic characters used for
the Lambeosaurinae.  I would like to point out that
these characters lend nothing to the analysis (with
the exception of 13, which is to distinguish their
state from other hadrosauroids, especially the
different states that vary within the Hadrosaurinae). 
Bolotsky and Godefroit should have not felt compelled
to include these characters unless they were going to
split the Lambeosaurinae into multiple OTUs in which
case, these characters would have actually been useful
in the analysis itself.  Anyway, the authors use five
autapomorphies to support the Lambeosaurinae.

-1- Maxillary shelf developed.
This character was referred to as a lambeosaurine
synapomorphy by Godefroit et al. 1998 (and also in
their 2001 paper) and has been used as one at least as
early as 1990 (Weishampel and Horner used it, for
instance, in their chapter on the Hadrosauridae in The
Dinosauria), however, it was not used in Godefroit et
al.'s lambeosaurine analyses until their 2003 paper. 
I'm not sure why they hestitated so long before
including it, and it is somewhat strange, since it is
stated as a lambeosaurine character in the text of
their 2001 paper on Charonosaurus.
-2- Rostral platform strongly excavated on the dorsal
aspect fo the frontal.
This character is coded incorrectly by the authors,
when they coded Lambeosaurinae as having the derived
state ("1"), when infact, the clade is polymorphic
("0/1"), since the plesiomorphic state is present in
the basalmost lambeosaurine Tsintaosaurus (Godefroit
et al. 2001; Godefroit et al. 2003).  This character
would have been more useful for joining Jaxartosaurus
and more derived lambeosaurines (as it is used in
Godefroit et al. 2003), had the authors split the
Lambeosaurinae into multiple OTUs.
-3- Ratio 'length/minimal width' of the parietal <2.
This character has been recognized for sometime as a
lambeosaurine synapomorphy, and there's nothing
especially worth commenting on the authors' use of it
that has not been already stated above.
-4- Lateral side of the squamosal elevated.
This character suffers from the same problem as 2.  It
isn't present in the two basalmost lambeosaurines,
Tsintaosaurus and Jaxartosaurus, and instead diagnoses
a more derived clade within the Lambeosaurinae, that
being Amurosaurus, the parasaurolophs, and the
corythosaurs (Godefroit et al. 2003). Again, it's
rather useless in the present analysis.
-5- Rostral process of the jugal rounded and
symmetrically very expanded.
This character has been recognized for a long time as
a lambeosaurine synapomorphy, though there's been some
argument over its use in the past, such as when it was
used to place Pararhabdodon in the Lambeosaurinae (a
placement that is not as spurious as thought by Head
2001).

Anyway, for those of you who have been waiting (like
myself) for the redescription of Amurosaurus, it's
time to start holding your breath folks. It's listed
in Bolotsky and Godefroit's bibliography as:

Bolotsky, Y.L., and P. Godefroit. In press.
Amurosaurus riabinini, a Late Cretaceous lambeosaurine
dinosaur from Far Eastern Russia. Acta Palaeontologica
Polonica.

I'm quite satisfied with where the authors have chosen
to publish their paper, as APP provides free access to
its papers, unlike the other journals that the authors
have been published in.

Nick Gardner

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