Re: Hanson 2006, Mortimer, Baeker response

["Jaime A. Headden" <qilongia@yahoo.com>]

David Peters (davidrpeters@earthlink.net) wrote:

<Most, if not all, dinos and pteros found today can be placed into existing
slots. Examples of new dinos include Lotosaurus and Silesaurus, but these have
been slotted into Ornithischia without a retro pubis.>

  *Lotosaurus* is allied to the crocodylomorphans. Dzik suggested that
*Silesaurus* could be an ornithischian if the dentary morphology and teeth were
to be held higher than the remainder of tis postcrania, but did not follow this
up with an out-and-out referral, while other analyses of both of these taxa
have failed to find this, though most were done outside of print and some
presented here onlist. The extremely primitive nature of the postcrania of both
of these animals would keep them outside of Ornithischia, since it's a group
comprised of its components, not of a single particular character or two (which
is itself highly convergent across all of Diapsida).

<Examples of new pteros include Austriadactylus, Bakonydraco and Pterorhynchus,
all of which have nothing else exactly like them, but can be slotted into an
existing cladogram.>

  YOUR existing cladogram? *Austriadactylus* is likely either *Preondactylus*
or another similar eudimorphodont. Hardly "nothing else," there, but I guess
that qualifier "exactly" can be used to escape this, just as it can be used to
escape ANYTHING definitive. Czerckas's pterosaur, I am not so sure. It doesn't
appear to be an amalgam, but I've not seen xrays to determine relative
densities of the slabs, and it appears singular and cohesive to my admittedly
untrained eye. However, what it appears to be is a long-tailed pterodactyloid,
so I think the transition from long to short tails is simply poorly documented
and this taxon, whatever it is, represents part of that transition.
*Bakonydraco* is an azhdarchid, as Osi, Weishampel and Jianu wrote in 2005,
given both the cervical and mandibular morphologies. The absence of a lot of
cranial material for most azhdarchids leaves its position to be founded largely
on the basis of the cervicals, while the jaw does appear to be highly similar
to *Azhdarcho* itself. I don't see what the problems here are, save for
Czerckas' taxon.

<If you have a cladogram that includes all known pterosaurs and you have one
MPT, plus the cladogram is chronologically correct and there are no untennable
reversals, then you've achieved your goal. Note that reversals are still
permitted, but untennable ones are not.>

  The fossil record is incomplete, so why should we expect the cladogram to be
temporally congruent? Indeed, this is one of the problems with the classic
series of horse and human evolution, which was hardly linear and "perfect" in
it's transitions, at the same time producing both dwarfism in the lineages,
robust taxa, and gracile taxa. That one can draw a line from beginning to end
is a product of evolution and hindsight, but the work to produce these lineages
was acheived of over a century of investigative phylogenetic research.
Pterosaurs have received much less in comparison, being farther from the mind
of us humans than ourselves. But dwarfism, and other forms of reversals, occur
periodically, and in some great abundance, for some reasons we don't know, as
the current debate on the Flores "hominid" is currently showing. So, too,
should pterosaurs be a wild and crazy bunch, and the deceit of a "perfect"
result makes me VERY suspicious.

<So, knowledge of the fossil record is incomplete in one sense, but complete in
another. Sorry. Some of the mystery is gone now.>

  In one's own mind perhaps. The fossil record will never be complete. New taxa
cannot be expect to simply "line up" or "slot in", as *Silesaurus* _clearly_
shows.

<You sound like a referee. Afraid of the 'danger' of finding a really good
cladogram.>

  I myself am afraid of the danger of someone saying they have a really good
cladogram. This is a personal deceit, that one mught think their result is so
clean or perfect as to not require introspection, or to simply start from
group-up and over again, in order to duplicate the results. One to dismiss
ephemeral "adults" and traced "characters" in order to advance one's own
knowledge, not just to satisfy a doubting few. If someone starts saying their
cladogram is "really good" because of their perfect MPT results and so-called
chronological linearity, then I would wash my hands of this. There are several
other cladograms out there, published, that contest this phylogeny, and we can
be self-assured this means no one has NEAR the perfect knowledge claimed by
Dave.

<Just as I have tested this cladogram in every way possible, this is a
challenge to others to let it get published and/or test it yourself.>

  The tracing method should be publically aired and scrutinized before your
results using it in a phylogeny published. This allows us to test the means by
which it seems a large number of the results have been produced from.
  
<A cladogram, I remind you, is a hypothesis. I promote this particular
hypothesis because it works in every way. A hypothesis doesn't prove anything,
but it is the best evidence (and usually they are widely accepted) that we
have.>

  An hypothesis is not evidence. The fossils are the evidence, and it's the
personal projection that the features have meaning that lend themselves to a
system of relationship. We have tested THAT particular interpretation to the
virtual satisfaction of the entire scientific community, but cladograms are a
way of doing this relationship-ratcheting algorithmically. That requires the
hypothesis that the algorithm represents an accurate means of deriving
information from the evidence, and that the results are a way to interpret it.
Thus a cladogram itself is also not evidence, but a projection of an
hypothesis, the hypothesis being the matrix (which is not available to us to
test). Since the very methods of deriving that matrix are at question, it would
be highly circumspect not to publish on the means prior to the ends.

<Let's say that No. 9 is a juvenile. What is it a juvenile form of? Be specific
and show evidence that it is indeed the candidate you propose and that it
doesn't have more evidence (remember parsimony) that it is closer to my
candidate.>

  It could be a juvenile of its own species. This doesn't stop it from being a
juvenile. It could be a juvenile of *Pterodactylus kochi*, not that I really
care, or of *P. antiquus*. But this doesn't stop it from being a juvenile. We
can also argue that the juvenile *P. micronyx* is a ctenochasmatid, but of what
more-nested is not certain, possibly either *Ctenochasma* or *Gnathosaurus* or
one of its relatives (parsimony would have us place it into an existing taxon
than coin a new one of equivalent standing, and it simply seems "cleaner" that
way to be LESS assumptive than MORE asusmptive about our taxonomy).

<Next point: do pterosaurs change their morphology during ontogenesis? Or not?
The embryos in eggs are the only known pterosaurs for which their ontogenetic
age is known precisely. Morphologically do they look like adults of one form or
another? Or are they unclassifiable? My evidence indicates that embryos look
like parents, and I used a cladogram. If embryos look like their parents, I
think we should expect that juveniles do too. Don't you?>

  The various authors of all the juvenile and embryo, near-hatchling pterosaurs
would argue that not only can these pterosaurs be shown to be embryos (as they
were before Dave said they were adults), but that their advanced limb
architecture and geometry was explainable through ordinary means and
hypotheses, as Unwin has done. The reasons are suited for more discoveries,
such as if there was creching, large nests, a single or a few eggs, parental
rearing or parental abandonmnet, which pterosaurs evidenced which, or something
else, etc. Perfect fossil record enough? No.

  Ontogeny also tells us juveniles do not look like adults. If the claim that
the limb proportions allow juvenile nesting to a volant adult, then this simply
means the wings have similar proportions and loading regimes, it says little
about the age of the animal, or even its phylogeny. Find a juvenile to support
the claim in the current environment, testably, or abandon it. This is science,
and the claim is an hypothesis driven into an hypothesis without even any
testing to determine its accuracy, which is not science.
 
<Again, no one making a cladogram cares what temperature pterosaurs were. But
you bring up an interesting point. What happens with baby sauropods versus big
sauropods? We know what size baby pterosaurs of any adult species were because
the egg chute has a limited aperture. We can start from there. Just think how
small a baby of a tiny pterosaur would have to be. Lizards are remarkable,
aren't they?>

  The homeothermy (or absence of it) in pterosaurs and its prescence throughout
ontogeny would be expected in an argument of flight-capable juveniles that were
precocial or super-precocial, and would require they were born highly active,
possibly without parental care, etc. This would also explain away virtually all
of Dave's hypotheses regarding juveniles appearing like adults, since the
body-size and mass relative to wingshape and loading will differ as the
pterosaurs scale up, and thus may not be phylogenetically informative without a
growth series. However, Dave's phylogeny does not look for a growth series, as
others have done outside of phylogeny, and this is a failing of the cladistic
system Dave is operating in, and was why Dr. Bäker spent half of his post
suggesting other paradigms to consider.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

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

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