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Re: Let's find the basal Ornithodire.
JH: I do not agree that a "juvenile phase" in *Longisquama* exists. The
highly eroded lower right edge of the holotypic slab, often showing entire
irregular sections missing (which Dave shows tracings overlying further
"fronds" extending), shows that if there was any material present
posterior to the dorsal series exposed, it would be within the slab, if
unprepared -- IF present.
DP: It's unprepared. A split slab only.
NO ONE has corroborated the increasing
"discoveries" of neonates, and apparently the entire absence of an
intermediate, initially ossifying, pterosaur non-adult.
DP: 2 reasons: 1) why raise your hand, if your're a professional, and say you
see something that only an amateur nutcase has seen. At present professionals
are not even _testing_ or _trashing_ my 2000 cladogram based on all previous
cladograms and easily visible materials and the literature. They're avoiding
it. Why? Professional issues? It's the strangest thing.
2) these images can only be seen _after_ they have been
traced. They are _that_ ephemeral. That's why so many things have been
overlooked. You need to see the real thing. Not a cast. As an aside, I found
the ascending process of the premaxilla, the complete left palate and the
occiput of Longisquama the fiftieth time I looked at the specimen. Why? Because
I didn't recognize these parts for what they were. The same thing occurs in
other ephemeral images. The same mental process occurred in the discovery of
theropod clavicles. Some things you don't recognize until you have your
ephiphany. And you actually have to do the work. I don't know _anyone_ who is
looking at Longisquama now. Lots of things are mistakenly identified at first.
The first found Rhamphorhynchus was a bird. One of the Archaeopteryx specimens
was a pterosaur. Everyone thought Jeholopterus had a half of a skull. Everyone
thought No. 9 was a juvenile. Etc. etc.
JH: As has been shown
by others and has yet to be refuted, juveniles with NO trace of
ossification post hatching OR post birth DO NOT delay ossification of
their bones; they are NOT mobile without hardened bones to support their
musculature and weight. This is a simple biological fact, and Dave does
not regard this strongly enough in light of the "neonates."
DP: Jaime you're a good candidate to learn to see ephemera. If you contact me
privately with a genuine interest, I'll take you on a tutorial.
<As in Longisquama. Not exposed in Sharovipteryx.>
JH: The sternal elements of *Longisquama* are not, in my opinion,
sufficiently oriented to show "broadening" as opposed to, say, a fully
terrestial lizard, with shorter forelimbs as hindlimbs. The prescence of a
lacertilian shoulder system, including a broad Y-shaped interclavicle.
*Megalancosaurus,* a dyed-in-the-wool arboreal or aquatic animal and
non-volant in any way, has a broader, if even MORE fixed shoulder
apparatus, and extremely elongated, broad sterna.
DP: The sternal elements are presented in full view ventrally. Sharov
illustrated them as such. I followed. Let me know specifically what you're not
seeing that has been reported in the literature.
<As in Longisquama and Cosesaurus. Not exposed in Sharovipteryx.>
JH: I don't agree with this assessment. The "keel" I see is a
misinterpretation of a dislocated or slightly separated interclavicle in
*Longisquama,* and the "nature" of a keel in *Cosesaurus* is
uncorroborated except in vague bright-exposure tracings, in which the
majority of the pectoral region is obscured beneath the holotype's
anterior dorsals and ribs.
DP: Well, I think you're agreeing with me, Jaime, because the keel is the
interclavicle. And in Cosesaurus the exposure is ventral, so the keel won't be
obscured beneath anything.
<covered above. shows up in juvie Longi.>
My refutation of this is above and elsewhere.
<by this you mean solidification of the ventral pelvis? If so, shows up in
Cosesaurus + L + S. by this you mean expansion of the anterior process of
the ilium? If so, ditto the above.>
JH: By the expansion of the sacrum, I referred to expansion of the sacrum,
i.e., incorporation of further central elements from the dorsal or caudal
series, from the general 1 or 2, up into 3, or four, as present in basal
DP: Peters 2000 counted extra sacrals in Cosesaurus. There's no doubt of extra
sacrals in Sharovipteryx. There are seven vertebrae between the extended ilia
in MPUM 6009, the basalmost pterosaur.
<not sure if anything in the dorsal spine is locked up in basal pteros.
Curious about this though. Please explain.>
JH: Rigidification of the dorsal series, aka, "locking up" occurs through
orientation of zygapophyses, development of addition vertebral processes
(zygosphenes, hyposphenes, xenarthrans, etc.,) -- this endorses reduction
of the flexibility of the spine (useful in a terrestrial biped or aquatic
animal with an elongated dorsum [if for instance that *Megalancosaurus* is
aquatic]). In basal pterosaurs, vertebrae become small, centra smaller --
they become essentially additional intervertebral articulations in the
style of the zygapophyses, and they bear condyle-in-socket intercentral
surfaces. This reduces much intervertebral movement. So far, such
vertebrae are unknown in proposed pterosaur ancestors. They retain
elongated "lizard-like" spines, with the sole exception of drepanosaurids,
in which the anterior dorsals are expanded in such a fashion to prevent
dorsiflexion. Such dorsiflexion (as well as latiflexion= turning to the
side) is a hazzard to a pre-pterosaur learning to fly.
DP: I cannot help you find what you're looking for. I haven't studied problems
related to spinal flexion in this clade. I can tell you that in basal
pterosaurs the spine is relatively short, as in immature Longisquama and as
opposed to adult Longisquama.
JH: If the arms are
already elongated in *Eudimorphodon* or *Preondactylus,* it stands to
reason that, along with the modifications to the vertebrae mentioned
above, the ancestor should have this, and as in birds, this may have
occured BEFORE the arms become effective aerial locomotors.
DP: You're using apriori assumptions. Again, long antebrachia are one of the
synapomorphies of the Pterosauria. Non- and pre- pterosaurs won't have them.
<They don't close up in basal pterosaurs. See Peters 2001. Historical
JH: These DO close up in pterosaurs:
DP: I hear what you're saying, but I'm saying they remain separated and
identifiable on the surface. Perhaps on the internal surfaces they are joined
in basal forms. I'll grant you that. Remember, some things like tail vanes and
syncarpals do show up later in pterosaurs, not in basal forms.
JH: they become fixed, locked elements that
serve a function: to prevent the wrist from moving in an entire plane,
normal in terrestrial animals for locomotion. Since pterosaurs rotate the
effective posture of the humerus lateral or dorsal 90 degrees to its
position in other terrestial animals,
DP: Whoa! Where did this come from?? They hold their arms like gunslingers do.
Or like bipedal lizards do. Or like birds and bats do.
JH: the "dorsal" side of the manus faces
DP: do you mean laterally (while standing)? or dorsally (while flying)?
JH: allowing flexion at the wrist ONLY inboard of the ulna.
DP: Inboard, you mean proximally? Proximal of the ulna? A little confused by
as pterosaurs, fuse or lock their wrists into effective "blocks,"
increasing as the pterosaurs got larger (i.e., towards Pterodactyloidea)
into a proximal and a distal block, instead of a set of distinct, but
"locked" elements of the ulnare, radiale, and all distal supra-metacarpal
<Actually its the elongation of the fourth metacarpal relative to I-III.
That's in L + S. And are there such things as proximal metacarpals? Did
you mean proximal carpals? If so, that's probably present in Longisquama,
but it's a bit messy around the wrist. And tiny.>
JH: My next question should have clarified this, but I do admit I was vague.
I mean reduction in mean size, reduction in diameter, circumference, area,
<In L + S. See pterosaurinfo.com>
JH: Not to the extent that ANY lizard doesn't get a long fourth : third
DP: True. But then, all I'm looking for is a longer fourth than third.
Impossible to find in Archosauriformes and especially Archosaurs. That's a big
JH: However, both *Longisquama* and *Sharovipteryx* do NOT
preserved osseous or even "impressed" material that ANY ONE ELSE has been
able to verify.
DP: Someone had to be first. I have been very open and public about what to
look for and where to find it (pterosaurinfo.com). No one is currently working
on this problem as far as I know. No one has disputed or come up with a more
precise tracing. Again, both are difficult, otherwise they would have been
<Am I the Dave you are referring to?>
<If so, can lizards draw the humerus close to the trunk? If so, then
Longisquama and Sharovipteryx could.>
JH: Indeed, the former is preserved in such a position, *Sharovipteryx* is
... equivocal ... depending on how much gratitude one gives to some of the
tracings I have seen on this, as well as my own observation: I have been
unable to find a complete antebrachium or humerus in the material though
what seems to be present is _typical_ for a quadrupedal lacertilian [and
I've seen a few].
DP: I'd be glad to review your Sharovipteryx tracings. Maybe you found
something I missed.
JH: My argument is that Dave has stated elsewhere that pterosaurs held their
humeri parallel to the trunk.
DP: Not sure that I remember this or espouse it now. In flight I do suggest
that the humeri were held about 40- 55º from the sagittal plane, a little
closer than others suggest (pterosaurinfo.com).
JH: I argue that this is NOT possible for the
majority of pterosaurs given the lateral orientation of the glenoid with a
limited caudal component, preventing the humerus from turning caudally in
the position Dave so often positions it in.
DP: Again, I'm not aware of any published, web or print, dorsal views that
you're referring to.
BTW, as a clarification, I write David Marjanovic for _that_ David, but
"Dave" for Dave Peters. Sorry for the confusion.
<Ah, Luke...look beyond the obvious. Start with the toes. Do your
cladogram. Let PAUP guide you. Sharovipteryx even has a long neck. It's
going off in another direction. Still, PAUP says it's a sister taxon.
Closer than almost anything else known to exist.>
JH: I don't have the ... patience ... to mess with PAUP* for the purpose of
plugging in material from elements gleaned from grain-sized structures in
slabs like that in the VERY SMALL *Sharovipteryx* holotype. My
examination, though brief, of a cast of the *Longisquama* holotype showed
that these slab structures are so ... irregular and massive in proportion
to the clear impressions that observations of other structures are
artefactual, not actual. This is a bias, I admit.
DP: The great thing about the new technique is that in messy cases like
Longisquama, the various visual layers one can construct can help visually
segregate this from that. The irregular and massive portion you refer to
<More importantly, if a taxon fulfilled ALL of your requirements, guess
what, it would be a pterosaur! You have to allow for something to evolve
from "not a pterosaur" to "a pterosaur". Think about the theropod-bird
connection and make the parallels in your mind work to accept this. Or try
JH: It may also be a bird. *Confuciusornis* satisfies these criteria.
DP: Tell me more. I can't imagine how, but I'm willing to learn.
JH: Not that I hold birds and pterosaurs as sister-groups, but this supports
these features would refutably infer the progression of a terrestrial or
aquatic animal into a volant, actively flighted animal. Since Heilmann, so
far every single "pro-avian" model has essentially conformed to dinosaurs.
Since Heilmann, no such progression has occured to produce a pre-pterosaur
intermediate between pterosaurs and ANY reptilian group, "ornithodiran,"
"protorosaurian," "prolacertiform," or otherwise.
DP: Why are you ignoring Peters 2000 and 2001? I found four.
JH: While I admire PAUP* for
the tool it is, I DO strongly stress that it is a tool, and not a means by
deriving an end-all hypothesis to be thrown up in support of any
relationship it may "support."
DP: At present it is the only tool we know that takes the bias out (as much as
that is possible), perhaps not when it is originally constructed by the biased
scientist who built it, but it can bias can easily be dissected from it via
review by others.
JH: As David said, one's data put into the
"machine" will get you your result.
DP: They why didn't Unwin and Kellner get more resolution out of their trees?
They didn't get the result they wanted.
JH: If you put a juvenile animal in it,
prepare to be surprised when it finds a juvenile grouped with adults of
the same species. Test this by using neotenic salamanders, hominids with
growth series, birds, cats, etc.
DP: I would expect the same. Juveniles should group with adults.
... Indeed, this response does help, but I fear it does not clarify my
position much clearer than has been said, and aside from my other post and
eventual response on neoteny/paedomorphism, I will not go further unless
more data is to be offered.
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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