Re: David Marjanovic's ptero comments

[David Marjanovic <david.marjanovic@gmx.at>]

> >>>>Very unlikely, because the picture in the pdf has very low resolution
(as,
> grrr, usual for Nature). There even is no way to see the papillar surface
> ornamentation on the eggshell fragment that is mentioned in the text and
> indicated in the close-up photo!!!

The jpg in the online full text is hardly better. It doesn't show the
papillae either -- it just shows that the surface isn't completely
homogenous.

> Easy David. I was thinking a pre-publication photo had to be floating
around.

Nature is good at keeping things secret.

> And besides, you would be stunned, as I was, what the pdf does reveal.

I can't believe that you can cut the pixels apart.

> DP > 1. the embryo is ossified
>
> DM >>>>>I hope so.
>
> This would imply post-independent or adult status in the radical
hypothesis.

Which has yet to explain how the poor beasties supported their own weight,
and how they were able to bite with their large teeth when the jaws were as
pliable as mammalian ears. Wait -- why can you see the teeth when no hard
material seems to be preserved?

> I know that in all other verts embryos develop bone tissue and I was
raised and educated on the notion that the same would hold true to
pterosaurs. The new hypothesis follows the observation of 40 examples, so I
can only follow and report the data. Although not a scientist, I play one on
the DML.

My argument isn't so much that all other vertebrates ossify early, but
rather that they _need to_ ossify early.

> DM [...] Eyes have strong negative allometry; small animals have
> proportionally bigger eyes than large ones.
>
> This suggested that we consider taxa that have, as adults, proportionately
large eyes, while still not rejecting the possibility that this is an
embryo.

Why should they have proportionately large eyes? Were all pterosaur babies
diurnal and all adults nocturnal?

> Again, I was raised and educated to consider all the  tiny forms with a
short rostrum and big eyes as juveniles. I was surprised as anyone to
discover that pterosaurs were somewhat different from the norm.

I'm not sure if the word "discover" is appropriate here.

> DP > In addition, the record of Wang and Zhou is not good with regard to
> > identifying pterosaurs and parts of pterosaurs.
>
> DP >>>>. Ad hominem argument. Pseudoscientific.
>
> A track record is a track record. Knowing beforehand that Wang and Zhou
appear to have less of an interest in pterosaurs than in birds suggests that
mistakes may be present here as well. What surprises me is your and others
faith-based approach to this problem. You read the text and accept it as
gospel.

Oh no. _In the absence of evidence to the contrary_, I _do_ take it at face
value what they write -- because I assume _they_ are scientists and _have
already_ done the science. Whether they're not so much interested in
pterosaurs, or have already misinterpreted others, doesn't matter. "Even a
blind chicken finds a grain once in a while" (forgot what the actual English
version is). Even Feduccia has gotten a few things right. :^)

Now _if_ evidence to the contrary is present, then I'll immediately stop
believing what they write. The question is whether such evidence is really
present, or whether you just interpret it into the texture and color of the
slabs.

> DP > Recent research has found
>
> DM  >>>> It's not good to imply that 5 or 10 researchers all over the
world have
> found them when this isn't the case. Why not "I have recently found"?
>
> No one is implying 5 or 10 anything. I, like other scientists, try to keep
the "I" out of it.

"Recent research has found" sounds very impersonal. It implies that it's a
general phenomenon that doesn't only involve one worker.

> DP > these unossified offspring
>
> DM >>>>>>Are you aware what this means? That they were all terminally
rachitic, and
> _suffering_ from it. Unable to support their own weight. Much like a
> stranded whale.
>
> You're making up this malady like a 17th century Puritan.

(17th? I'm more talking about the 19th century, when all those kids in the
dark factories weren't able to produce enough vitamin D and therefore had
problems getting calcium into their bones, which were then bent by their
body weight.)

> The evidence says that most baby pterosaurs were just fine. Why they did
not have bones the color of their mother's remains to be discovered.

First of all, you should demonstrate that those babies actually exist. If no
bones are there, we don't need to discuss their color or material.

> DP > In <i>Cosesaurus</i> a ruptured sac is visible within the mother's
torso,
>
> DM >>>> If such a thing is preserved, then where are all the inner organs?
Why
> doesn't it _at least_ look like *Scipionyx*?
>
> Why don't you look at the specimen? Maybe I missed something beneath all
that gastralia. If a jellyfish was preserved on the same slab, surely a
liver and some kidneys should be prominent. For the moment, though, the
subject is reproduction.

Gastralia? I can barely see the ribs on this coarse-grained slab with
millimeter-sized pixels!

I can see the skull of the baby that's being born. It just looks unreal. I
bet that, if seen from a different angle, it would _disappear_. Like the
face on Mars. The grainy texture of the matrix _begs_ for being interpreted
in terms of shapes. I've found a V-shaped thing under the "sternal ribs"
that, at second glance, just isn't there -- its lower branch consists of
three individual hills that are not connected in any way.

> DP > a half-size juvenile
>
> DM >>>> An unossified juvenile half the size of an adult? What have I
misunderstood
> here?
>
> [...] It falls within the typical pterosaur pattern of development.

Then, really, how did it _survive_?

> DP > Relatively short snouts and large orbits place these tiny adults
close
> > to <i>Scaphognathus</i> and <i>Dorygnathus</i> in cladistic analysis.
>
> DM >>>>These features are classical features of juveniles, see above.
>
> True, and as I said before, everyone was raised on this, including your
truly. Perhaps that's why the wee ones were ignored in cladistic analysis.
However, taking the chance that something might be learned, I inserted a
number of these tiny pteros into the matrix and came up with new
perspectives on pterosaur phylogeny (see pterosaurinfo.com > taxa > family
tree). As in pre-mammals > early mammals, a size squeeze appears to have
facilitated the development of pterodactyloid-grade characters in four
lineages of pterosaurs. Again, and before you get all huffy about having
your dogma shaken, I urge you to approach this like a scientist, instead of
a priest of the Inquisition. Gather the data, create the matrix, see what
shakes out. "The times they are a changin'." It took me a few years of head
scratching to come up with this. But I offer it to you freely.

Keep in mind, though, that cladistics is COMPLETELY INCAPABLE of telling
which characters are ontogenetic. It isn't capable EITHER WAY of doing
anything about this problem.

> DP > Pterosaur offspring do not have proportionately larger eyes.
>
> DM >>> See above for why this is _funky_.
>
> Also see above. This too comes from observation â?"â?" not a politicized
notion of what "should" be.

My interpretation comes from the hypothesis of why large eyes should and
should not exist, not so much from where they exist.

> DP > At birth the wing finger may
> > be relatively longer than that of the parent
>
> DM >>> While the animal is unable to fly???
>
> See my article in Prehistoric Times for a take on this (pterosaurinfo.com
> news). No one knows why.

This article doesn't give any speculation for why this should be so. It
doesn't even mention the problem.
        Besides, it assumes a lake bottom to be a beach... and it begins in
such an unpersonal style that every reader must assume what you write were
common textbook wisdom. Modesty is not scientific. When you have found
something, write so!

> It's just an hypothesis.

If the flightless babies have a fully developed flight apparatus, then
probably something is wrong with the hypothesis.

> DP  > The data shows that no
> > more than two juveniles and two embryos are present, except in breeding
> > grounds where the matrix may be littered with abandoned babies.
>
> DM >>>>Why "abandonded"?
>
> Sadly, some offspring, for whatever reason, were unable to hitch a ride on
their mother. Left behind as she flew off from the breeding ground/rookery,
they died. > Natural selection at its best.

Yes, natural selection _against_ a long wing-finger which hindered climbing!

> DP > As in bats, offspring clung to the mother, apparently beneath
> > her and oriented posteriorly.
>
> DM >>>>> Not obvious from those of your tracings that I've seen.
>
> Rarely are the juveniles actually attached to their mothers insitu. I've
seen it in Zhejiangopterus and Rhamphorhynchus. Since writing this, however,
the tall crested nycto baby showed up.

And from these three you generalize?

> DP > Delayed ossification facilitated the
> > development of extremely thin-walled hollow bones.
>
> DM >>>>>>No, the development of severe rachitis. Pneumatic bones are
formed by air
> sacs _destroying present bone_, not by bone growing as a tube.
>
> I'm guessing that the long bones of baby pterosaurs already had air sacs
in place, and that what we are seeing, as in the adults, are collapsed
tubes.

Imagine a cartilage tube with walls perhaps 100 µm in thickness. (The
cartilage of your ears is easily 10 times that thick, and quite pliable.) If
it's a weight-bearing bone, it will assume a _balloon_ shape under the
weight of the animal.

Is anything known on the ontogeny of pneumaticity in pterosaurs? In
dinosaurs dead and alive, pneumaticity comes long after ossification.

> I'm glad you're this interested in pteros, David. And a good challenge is
better than coffee in the morning.

I can't judge this. I don't drink coffee. Coffee smells much better than it
tastes. :-)

BTW... the diameter of the egg is not 41 mm at all. It's squished flat so
that it now measures 41 mm in width and perhaps 5 mm in height... when these
two measurements should have been equal in vivo.