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Re: =?unknown?b?TPw=?= and Li 2006, a review

David Peters (davidrpeters@earthlink.net) wrote:

<1. Well, the choice of the outgroup taxa dooms the base of this study from the
start. Pterosaurs are lizards, not archosaurs as shown by a cladistic analysis
2 to 14 times larger and more inclusive than any prior attempt at classifying

  I doubt whether the outgroup would have influenced the deeper arrangements of
pterosaurs much at all, though it might shift the base around a little.
However, anyone is welcome to test this by actually adding in taxa to the
matrix (and code accordingly) to determine if there is fault in the outgroup.

<2. 34,000 most parsimonious trees were found and that's because the limit of
the Max Tree was set at 34,000. Wow. That should be a huge red flag that
something is rotten in this tree and more work needs to be done.>

  If I got to 34,000 max trees on my result, I'd realize that little would
result in fewer trees unless I started un-zeroing entries, which in the
authors' cases would mean pretending that some specimens were clearer or more
complete than they really are.

<3. As usual, the highly derived pterosaur, Rhamphorhynchus, is shown to be the
sister group to the classic 'Pterodactyloidea' when anyone with an eyeball
would be hard-pressed to find a synopomorphy or two uniting the two. In an
unpublished cladistic analysis of greater breadth, Rhamporhynchus is a highly
derived dead end leaving no progeny and the pterodactyloid grade arises four
times by convergence from dorygnathids twice and via basal dorygnathids, from
scaphognathids twice.>

  It's a "highly derived dead end" in EVERY cladistic analysis to include it,
which comes from the nature of it's peculiar cranial anatomy. Less confusing, I
am sure, is the more plesiomorphic postcrania. Then again, pterosaurs like
*Dorygnathus* and *Sordes* has very similar jaws and skull structure, so I
doubt Rhamphorhynchidae is very incoherent in the current pterosaur
environment. As for the polyphyletic treatment of some clades, one must wait
for testable, available results to consider claims of such oddity, if indeed
such would exist.

<5. No tiny pterosaurs (typically known from numbers rather than names) were
included, which also screws up the results royally. Tracings of pterosaurs in
eggs show that their proportions do not differ greatly from their parents, so
any so-called assignments of short-rostrum 'juveniles' to long-rostrum 'adults'
are false and misleading.>

  These specimens are not included for what, it seems to me, is a VERY good
reason: they are considered juveniles by just about every pterosaur worker out
there. Not because they assume it to be true, but because a good deal of work
has gone into considering them and relegating them as juveniles, even if
taxonomic assignment can be shaky (which it may be). Only one person it seems
considers them adults, and for reasons that it would appear NO ONE agrees with
him on (that no one referring to pterosaur workers or anyone who's looked into
the situation). Finding proof these aren't juveniles would be considerable, but
so far, no data demonstrating this has been published. The paper Dave published
on a few juveniles found inside eggshells are just that, juveniles inside
eggshells. Additionally, "ephemera" (that which disappears with a second look)
do not prove the adulthood of an adjacant specimen. So, there is good reason
not to include these specimens in a matrix. If anything, this inclusion is what
I suspect is resulting in the rather topsy-turvy result of "pterodactyloidea"
and non pterodactyloid pterosaurs in Dave's own analyses (testing to this idea
would require REMOVING THEM to see the results).


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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