development of feathers in evolution analyzed at the molecular level
Kent Paul Dolan
during feather growth and development, filled in
with connecting material, spaces then created by
cell aptosis under a particular molecular control,
so a more primitive ancestoral "feather" may well
have _been_ a membrane, making even characterizations
of Longisquama's integumentary appendages as
"membraneous" not disqualifying for them still being
early versions of feathers.
"We show that the antagonistic balance
between noggin and bone morphogenetic
protein 4 (BMP4) has a critical role in
feather branching, with BMP4 promoting
rachis formation and barb fusion, and noggin
enhancing rachis and barb branching.
Furthermore, we show that sonic hedgehog
(Shh) is essential for inducing apoptosis of
the marginal plate epithelia, which results
in spaces between barbs."
And also:
"Our data suggest that a radially symmetric
feather is more primitive than the
bilaterally symmetric feather in terms of
molecular and developmental mechanisms, and
may have been the prototype of feathers.
Some fossilized primitive skin appendages on
Sinornithosaurus also favour this model.
Further modulation of BMP and Shh pathways
may have led to the many varieties of
feather seen today by regulating the number,
shape and size of the rachis, barbs, and
barbules1,17,30. This work provides evidence
for the molecular mechanisms possibly
involved in the evolution of feather
branching."
http://www-hsc.usc.edu/~cmchuong/nature.pdf
It's a good read, not that I can claim to understand
all the details of the biochemistry involved.
Valeat quantum valere potest.
xanthian.
Augray
wrote in <1176540030.5...@d57g2000hsg.googlegroups.com> :
>The spaces between barbs in feathers are initially,
>during feather growth and development, filled in
>with connecting material, spaces then created by
>cell aptosis under a particular molecular control,
>so a more primitive ancestoral "feather" may well
>have _been_ a membrane, making even characterizations
>of Longisquama's integumentary appendages as
>"membraneous" not disqualifying for them still being
>early versions of feathers.
The authors of the paper believe this to be unlikely. Besides, cell
death allows the barbs to spread out, thereby increasing the width of
the resulting feather. If the feather was a continuous membrane, its
width would be equivalent to the circumference of the follicle it grew
from. There's also the problem of how a "membraneous" feather could
make the transition to a modern feather and still perform its function
in the interim.
> "We show that the antagonistic balance
> between noggin and bone morphogenetic
> protein 4 (BMP4) has a critical role in
> feather branching, with BMP4 promoting
> rachis formation and barb fusion, and noggin
> enhancing rachis and barb branching.
> Furthermore, we show that sonic hedgehog
> (Shh) is essential for inducing apoptosis of
> the marginal plate epithelia, which results
> in spaces between barbs."
>
>And also:
>
> "Our data suggest that a radially symmetric
> feather is more primitive than the
> bilaterally symmetric feather in terms of
> molecular and developmental mechanisms, and
> may have been the prototype of feathers.
Which is not a surprise.
> Some fossilized primitive skin appendages on
> Sinornithosaurus also favour this model.
> Further modulation of BMP and Shh pathways
> may have led to the many varieties of
> feather seen today by regulating the number,
> shape and size of the rachis, barbs, and
> barbules1,17,30. This work provides evidence
> for the molecular mechanisms possibly
> involved in the evolution of feather
> branching."
>
>http://www-hsc.usc.edu/~cmchuong/nature.pdf
>
>It's a good read, not that I can claim to understand
>all the details of the biochemistry involved.
I'm not sure that anyone does at this point. But it demonstrates that
the presence or absence of certain proteins can affect the development
of feathers.
Kent Paul Dolan
> "Kent Paul Dolan" <xanth...@well.com> wrote:
>> The spaces between barbs in feathers are
>> initially, during feather growth and development,
>> filled in with connecting material, spaces then
>> created by cell aptosis under a particular
>> molecular control, so a more primitive ancestoral
>> "feather" may well have _been_ a membrane, making
>> even characterizations of Longisquama's
>> integumentary appendages as "membraneous" not
>> disqualifying for them still being early versions
>> of feathers.
> The authors of the paper believe this to be unlikely.
I didn't see that in the paper, but my eyes were
glazing over pretty badly. Was it in there, or is
that some special "private communication" knowledge
you possess?
> Besides, cell death allows the barbs to spread
> out, thereby increasing the width of the resulting
> feather.
> If the feather was a continuous membrane, its
> width would be equivalent to the circumference of
> the follicle it grew from.
Yes, but that could have been accomodated in
evolution by the inner circumference of the follicle
being convoluted rather than smooth, or by the
follicle circumference being very large during
feather growth and shrinking back to the size of the
quill base when that growth was complete; compare to
the dilation and later shrinkage of the human cervix
during birth. Nature chose cell aptosis instead, but
it isn't the only conceivable solution to getting
wide feathers out of a narrow follicle.
Notice also that your statement is in part an
argument toward a refutation of the claims in
http://www.erin.utoronto.ca/~w3reisz/pdf/Longis.pdf
that what we are seeing in Longisquama's
integumentary appendages is a membrane, for exactly
the same reasons. The sheer developmental
improbability of designing a follicle that would
grow that appendage as two membranes plus a quill,
in a figure eight cross-section, as that paper
claims it to be, is a further argument against the
claims in the above paper.
> There's also the problem of how a "membraneous"
> feather could make the transition to a modern
> feather and still perform its function in the
> interim.
That's a "problem", but it isn't a show stopping
one, it's just one more question to which we don't
yet have an answer. For one thing, we'd first have
to know what the "function" was as a membranous
feather. If it were for sexual display, the
transition wouldn't be particularly challenging.
If it were for trapping air against the body for
insulation, the transition would improve the
functioning. You only have real problems that I can
infer if the feather is in fact a flight feather in
its membraneous form. That transition would be a
tough one indeed.
>> "We show that the antagonistic balance between
>> noggin and bone morphogenetic protein 4 (BMP4)
>> has a critical role in feather branching, with
>> BMP4 promoting rachis formation and barb
>> fusion, and noggin enhancing rachis and barb
>> branching. Furthermore, we show that sonic
>> hedgehog (Shh) is essential for inducing
>> apoptosis of the marginal plate epithelia,
>> which results in spaces between barbs."
>> And also:
>> "Our data suggest that a radially symmetric
>> feather is more primitive than the bilaterally
>> symmetric feather in terms of molecular and
>> developmental mechanisms, and may have been the
>> prototype of feathers.
> Which is not a surprise.
Well, maybe not a surprise, but useful if true.
A radially symmetric feather would be useless for
flight or cursorial steering, fair for streamlining,
marginal for sexual display, but splendid for
insulation.
If we grant their deductions, that gives us a pretty
strong couple of guesses at the original purpose
feathers served, and eliminates others.
>> Some fossilized primitive skin appendages on
>> Sinornithosaurus also favour this model.
>> Further modulation of BMP and Shh pathways may
>> have led to the many varieties of feather seen
>> today by regulating the number, shape and size
>> of the rachis, barbs, and barbules1,17,30. This
>> work provides evidence for the molecular
>> mechanisms possibly involved in the evolution
>> of feather branching."
>> http://www-hsc.usc.edu/~cmchuong/nature.pdf
>> It's a good read, not that I can claim to
>> understand all the details of the biochemistry
>> involved.
> I'm not sure that anyone does at this point. But
> it demonstrates that the presence or absence of
> certain proteins can affect the development of
> feathers.
And indeed of all of ontogeny, but the useful
factoid from the evolution viewpoint is that these
chemicals and/or their follicle concentration
levels can have been evolved specifically for, or
more likely received new uses in, the evolution of
feathers.
Quantum valeat.
xanthian.
Augray
wrote in <1176635422.1...@l77g2000hsb.googlegroups.com> :
>Augray <aug...@sympatico.ca> wrote:
>> "Kent Paul Dolan" <xanth...@well.com> wrote:
>
>>> The spaces between barbs in feathers are
>>> initially, during feather growth and development,
>>> filled in with connecting material, spaces then
>>> created by cell aptosis under a particular
>>> molecular control, so a more primitive ancestoral
>>> "feather" may well have _been_ a membrane, making
>>> even characterizations of Longisquama's
>>> integumentary appendages as "membraneous" not
>>> disqualifying for them still being early versions
>>> of feathers.
>
>> The authors of the paper believe this to be unlikely.
>
>I didn't see that in the paper, but my eyes were
>glazing over pretty badly. Was it in there, or is
>that some special "private communication" knowledge
>you possess?
Nothing private, but it is admittedly near the end of the paper, when
any eye glazing is likely to be at its peak:
On the basis of some fossil evidence it has been proposed that a
filamentous integument structure with a major central shaft and
notched edges may be the prototype of feathers
Items 8 to 10 in the reference list are cited, number 8 being the
Jones et al. Longisquama paper. Number 9 also concerns Longisquama.
The authors continue:
According to this model, the rachis would have formed first in
evolution, then barbs, and finally barbules. Therefore, the
rachis and barbs would be different entities and not
interchangable (Fig. 5c). Alternatively, because barbs form first
during development, it was proposed that barbs appeared first in
integument evolution, and the rachis, a specialized form of fused
barbs, appeared later as an evolutionary novelty
More cites are now given. And now the critical sentence:
The fact that the barbs and the rachis can be converted
experimentally in the laboratory favours the barb to rachis
model.
In addition:
Our data suggest that a radially symmetric feather is more
primitive than the bilaterally symmetric feather in terms of
molecular and developmental mechanisms, and may have been the
prototype of feathers (Fig. 5c). Some fossilized primitive skin
appendages on Sinornithosaurus also favour this model.
Since the appendages of Longisquama are already bilaterally
symmetrical, this argues against any homology as well.
>> Besides, cell death allows the barbs to spread
>> out, thereby increasing the width of the resulting
>> feather.
>
>> If the feather was a continuous membrane, its
>> width would be equivalent to the circumference of
>> the follicle it grew from.
>
>Yes, but that could have been accomodated in
>evolution by the inner circumference of the follicle
>being convoluted rather than smooth,
I'll have to think on that.
>or by the
>follicle circumference being very large during
>feather growth and shrinking back to the size of the
>quill base when that growth was complete; compare to
>the dilation and later shrinkage of the human cervix
>during birth.
While such a scenario is certainly imaginative, I have to admit that I
find it doubtful. Looking at the picture in Reisz & Sues (URL down
below), the maximum width of the appendage is roughly one centimeter,
which would give a follicle diameter of about 3 millimeters. But in
figure 2 of Jones et al. (at
http://arnica.csustan.edu/jones/Publications/pdf/Longisquama.pdf for
anyone who missed this in another thread) one can see that the bases
of the appendages are separated from each other by a distance that's
smaller than that. Hence such dilation would cause the follicles to,
shall we say, "overlap".
>Nature chose cell aptosis instead, but
>it isn't the only conceivable solution to getting
>wide feathers out of a narrow follicle.
>
>Notice also that your statement is in part an
>argument toward a refutation of the claims in
>
>http://www.erin.utoronto.ca/~w3reisz/pdf/Longis.pdf
>
>that what we are seeing in Longisquama's
>integumentary appendages is a membrane, for exactly
>the same reasons. The sheer developmental
>improbability of designing a follicle that would
>grow that appendage as two membranes plus a quill,
>in a figure eight cross-section, as that paper
>claims it to be, is a further argument against the
>claims in the above paper.
You assume that they grew from follicles, and this is by no means
agreed upon.
>> There's also the problem of how a "membraneous"
>> feather could make the transition to a modern
>> feather and still perform its function in the
>> interim.
>
>That's a "problem", but it isn't a show stopping
>one, it's just one more question to which we don't
>yet have an answer. For one thing, we'd first have
>to know what the "function" was as a membranous
>feather. If it were for sexual display, the
>transition wouldn't be particularly challenging.
>If it were for trapping air against the body for
>insulation, the transition would improve the
>functioning.
How?
>You only have real problems that I can
>infer if the feather is in fact a flight feather in
>its membraneous form. That transition would be a
>tough one indeed.
So, if the appendages are indeed membranous, they weren't used for
flight?
>>> "We show that the antagonistic balance between
>>> noggin and bone morphogenetic protein 4 (BMP4)
>>> has a critical role in feather branching, with
>>> BMP4 promoting rachis formation and barb
>>> fusion, and noggin enhancing rachis and barb
>>> branching. Furthermore, we show that sonic
>>> hedgehog (Shh) is essential for inducing
>>> apoptosis of the marginal plate epithelia,
>>> which results in spaces between barbs."
>
>>> And also:
>
>>> "Our data suggest that a radially symmetric
>>> feather is more primitive than the bilaterally
>>> symmetric feather in terms of molecular and
>>> developmental mechanisms, and may have been the
>>> prototype of feathers.
>
>> Which is not a surprise.
>
>Well, maybe not a surprise, but useful if true.
Agreed. I was merely remarking that the claim is in accordance with
what we find in the fossil record if Longisquama is assumed not to
have feathers.
The chemicals themselves seem to have evolved to regulate the growth
of bone and the nervous system.
>Quantum valeat.
>
>xanthian.
JTEM
> If we grant their deductions, that gives us a pretty
> strong couple of guesses at the original purpose
> feathers served, and eliminates others.
You're a monkey raping psycho, but you usually post
the more provocative cites, so I thought I'd post
something that should give you reason to pause:
http://www.geotimes.org/june02/WebExtra0627.html
What you should -- though doubtless won't -- take
from this:
How do you judge fossil evidence? If you want
us to accept one fossil (or, more accurately, the
interpretation there of), it's incumbant upon you to
accept all the others. This gets a little difficult after
a while, because of the inevitable (but not always
in the way you expect) conflicts.
If the above tracks were a contemporary of
archaeopteryx they would fit into prevailing views
quite easily. Hasn't it often been suggested that --
because of size and/or habitat -- early birds may
not have fossilized easily? And here we'd have
tracks, but no birds, kind of proving it....
"Well, we know the birds were there, living
everywhere from Germany to South America,
because we've found the tracks in South America
even if we don't have any fossils of the birds
themselves!"
No, I'm not saying that you're required to accept
these tracks as "proof" that birds pre-date... well...
they predate themselves, according to prevailing
views. All I'm saying is that you have to look at
ALL fossils the exact same way, with the exact
same critical eye. And, you have to be ready,
willing & able to articulate your reasons for
accepting one while rejecting another, and you
have to be able to defend those reasons.
Kent Paul Dolan
>> If we grant their deductions, that gives us a
>> pretty strong couple of guesses at the original
>> purpose feathers served, and eliminates others.
> but you usually post the more provocative cites,
> so I thought I'd post something that should give
> you reason to pause:
> http://www.geotimes.org/june02/WebExtra0627.html
> What you should -- though doubtless won't -- take
> from this:
What, accept your broken-brained reasoning? You're
right, I won't. Nor will any other intelligent reader here.
> How do you judge fossil evidence? If you want
> us to accept one fossil (or, more accurately, the
> interpretation there of), it's incumbant upon you to
> accept all the others.
No, moron, it is _not_ incumbant on _anybody_ to
accept _every_ speculation on every fossil.
Just because you lack the ability to distinguish
between drivel and science doesn't mean the
_intelligent_ people here do.
This is an excellent example of why your broken
thinking and industrial strength stupidity leads you
to prating inanities here so consistently while
evading all responsibility to document your claims.
> This gets a little difficult after a while,
> because of the inevitable (but not always in the
> way you expect) conflicts.
Resolving conflicts is what logical thought is all
about, but again, having no experience with logical
though, you wouldn't know that.
> If the above tracks were a contemporary of
> archaeopteryx they would fit into prevailing views
> quite easily. Hasn't it often been suggested that --
> because of size and/or habitat -- early birds may
> not have fossilized easily? And here we'd have
> tracks, but no birds, kind of proving it....
Um, you did bother to _read_ that article, didn't
you? None of the scientists are claiming those _are_
bird tracks (and some features of those tracks are
described that are in conflict with classifying them
as bird tracks), only that they need more study
because of the possibility that they _might be_ bird
tracks, or might well be something else entirely.
> "Well, we know the birds were there, living
> everywhere from Germany to South America,
> because we've found the tracks in South America
> even if we don't have any fossils of the birds
> themselves!"
Shorebirds, leaving tracks in lakeshore mud, do
indeed have a good chance that their tracks will be
fossilized, especially if the lake drains suddenly
due to something like rupture of a natural or
animal-built dam, so that their tracks dry
undisturbed.
This ability to find tracks of real birds where no
real bird fossils have been found (remember, birds
are very mobile, they may well die far from where
they walk, remember bird bones are very light and
therefore fragile with respect to crushing by larger
animals via chewing or just stomping) lends exactly
no support to any contention of yours.
> No, I'm not saying that you're required to accept
> these tracks as "proof" that birds pre-date...
> well... they predate themselves, according to
> prevailing views.
No, moron, no one says that, you just use it as one
of your idiotic strawmen because you cannot
understand what _is_ being claimed, due, again, to
your military grade stupidity.
> All I'm saying is that you have to look at
> ALL fossils the exact same way, with the exact
> same critical eye.
No, "you" don't. Intelligence is all about learning
how to distinguish between seemingly similar cases.
Lacking any intelligence, of course you wouldn't
know that from personal experience.
> And, you have to be ready, willing & able to
> articulate your reasons for accepting one while
> rejecting another, and you have to be able to
> defend those reasons.
Of course you do, and of course you, JTEM, refuse to
defend your "reasons", say, your reasons for
claiming that tens-of-tons creatures that reach
adulthood rapidly do not, thereby, lend credence to
claims that they were warm-blooded. Or have you
found that missing evidence to support your lies
that dinosaur era tens of tons crocodilians also
reached adult size rapidly?
Vae victis, JTEM, vae victis.
xanthian.
Kent Paul Dolan
I don't see the logic here. If what Longisquama
displays is what I see, a fully developed rachis and
barbs, but lacking barblets and hooks, that is
already a developed set, and the stage the authors
describe of hair-like barbs evolving to be colliding
in the follicle to create the rachis "quill" would
have long preceded it in evolutionary time.
If instead it is a (single thickness, by the logic I
explained earlier) membrane which collided to form a
rachis just as barbs in feather follicles do today,
there's nothing to prevent the aptosis that turned
the membrane into barbs from evolving later in time,
and what are now barbs and rachis being
interconvertable. Remember, in current feathers, the
rachis isn't a real separate thing, it is just the
bases of a bunch of barbs that collided and merged
together.
There's not that much difficulty in the membrane
coming from a follicle much smaller circumferance
than the membrane's width. Plant leaves do the same
trick everywhere today, by growing as two rolled
surfaces with a central rib, which unfurls as it
emerges from its narrow bud. When the Longisquama
purported membrane changed later in evolution to a
phalanx of barbs, growing out, remember, base first,
the growth base could have simplified from two
spirals to one circle. We lack the soft tissue
fossil samples in detail great enough to distinguish
the cases.
> In addition:
>: Our data suggest that a radially symmetric
>: feather is more primitive than the bilaterally
>: symmetric feather in terms of molecular and
>: developmental mechanisms, and may have been the
>: prototype of feathers (Fig. 5c). Some fossilized
>: primitive skin appendages on Sinornithosaurus
>: also favour this model.
> Since the appendages of Longisquama are already
> bilaterally symmetrical, this argues against any
> homology as well.
Again, you're assuming the "membrane" interpretation
of Longisquama's "integumentary appendages", but
that's surely not what the photos in the original
paper depict: those are barbs, not "corrugations".
>>> Besides, cell death allows the barbs to spread
>>> out, thereby increasing the width of the
>>> resulting feather.
>>> If the feather was a continuous membrane, its
>>> width would be equivalent to the circumference
>>> of the follicle it grew from.
>> Yes, but that could have been accomodated in
>> evolution by the inner circumference of the
>> follicle being convoluted rather than smooth,
> I'll have to think on that.
Much like the interior surface area of a lung is
huge, of a charcoal briquette is enormous, making
something convoluted enough gives it "fractal
dimension", where lots of line can be squashed into
very little area or lots of surface into very little
volume.
>> or by the follicle circumference being very large
>> during feather growth and shrinking back to the
>> size of the quill base when that growth was
>> complete; compare to the dilation and later
>> shrinkage of the human cervix during birth.
> While such a scenario is certainly imaginative,
Why thank you. I'm just proud that evidence of it in
animal organisms is widespread and has been since
the first egg was laid.
> I have to admit that I find it doubtful. Looking
> at the picture in Reisz & Sues (URL down below),
> the maximum width of the appendage is roughly one
> centimeter, which would give a follicle diameter
> of about 3 millimeters. But in figure 2 of Jones
> et al. (at
. http://arnica.csustan.edu/jones/Publications/pdf/Longisquama.pdf
> for anyone who missed this in another thread) one
> can see that the bases of the appendages are
> separated from each other by a distance that's
> smaller than that. Hence such dilation would cause
> the follicles to, shall we say, "overlap".
Well, you're assuming that in life the follicles
were in a single row, but they may well have been in
two or more staggered rows, flattened at
fossilization time into a nicely intercalated single
row by compression and the tendency of the
sturderier quill bases to mold and push aside the
flesh. That's speculation, but not too far fetched.
Anyway, I'm going to continue to contend that what
Longisquama had was already highly evolved rachis
and barb feathers, just with the outer tips of the
barbs merged for reasons I explained in an earlier
posting. The rest of this is just to try to make
developmental peace with those who claim that's a
membrane, by describing several ways it could have
grown. Since we _do_ see follicles, and we _do_ see
the appendages, we are at least guaranteed that
whatever the character of the appendages, it was
_somehow_ possible for them to grow from those
follicles.
>> Nature chose cell aptosis instead, but it isn't
>> the only conceivable solution to getting wide
>> feathers out of a narrow follicle.
>> Notice also that your statement is in part an
>> argument toward a refutation of the claims in
>> http://www.erin.utoronto.ca/~w3reisz/pdf/Longis.pdf
>> that what we are seeing in Longisquama's
>> integumentary appendages is a membrane, for
>> exactly the same reasons. The sheer developmental
>> improbability of designing a follicle that would
>> grow that appendage as two membranes plus a
>> quill, [and therefore] in a figure eight
>> cross-section, as that paper claims it to be, is
>> a further argument against the claims in the
>> above paper.
> You assume that they grew from follicles, and this
> is by no means agreed upon.
Sure it is, the follicles are visible in the fossil,
and that part of the "integumentary appendages" maps
extremely well to the same parts of modern bird
feathers. Look at the photo captions again.
>>> There's also the problem of how a "membraneous"
>>> feather could make the transition to a modern
>>> feather and still perform its function in the
>>> interim.
>> That's a "problem", but it isn't a show stopping
>> one, it's just one more question to which we
>> don't yet have an answer. For one thing, we'd
>> first have to know what the "function" was as a
>> membranous feather. If it were for sexual
>> display, the transition wouldn't be particularly
>> challenging. If it were for trapping air against
>> the body for insulation, the transition would
>> improve the functioning.
> How?
The same way attic spun glass insulation has more
insulating value than an equal weight per surface of
the attic of a single sheet of plate glass. The
trapped air acts as more insulation than the glass
alone, and the more "fractal" the trapping agent,
the more air gets trapped.
>> You only have real problems that I can infer if
>> the feather is in fact a flight feather in its
>> membraneous form. That transition would be a
>> tough one indeed.
> So, if the appendages are indeed membranous, they
> weren't used for flight?
That isn't claimed for Longisquama anyway, the claim
is that they may have been gliding appendages. If
so, membranes like those stretched between the legs
or toes of many gliding species suffice just fine,
so no, being membranous doesn't disqualify them from
being instruments of flight. That's one of the open
issues about Longisquama.
>>>> "We show that the antagonistic balance
>>>> between noggin and bone morphogenetic protein
>>>> 4 (BMP4) has a critical role in feather
>>>> branching, with BMP4 promoting rachis
>>>> formation and barb fusion, and noggin
>>>> enhancing rachis and barb branching.
>>>> Furthermore, we show that sonic hedgehog
>>>> (Shh) is essential for inducing apoptosis of
>>>> the marginal plate epithelia, which results
>>>> in spaces between barbs."
>>>> And also:
>>>> "Our data suggest that a radially symmetric
>>>> feather is more primitive than the
>>>> bilaterally symmetric feather in terms of
>>>> molecular and developmental mechanisms, and
>>>> may have been the prototype of feathers.
>>> Which is not a surprise.
>> Well, maybe not a surprise, but useful if true.
> Agreed. I was merely remarking that the claim is
> in accordance with what we find in the fossil
> record if Longisquama is assumed not to have
> feathers.
Um, no, you're still confused by the debunkers' idea
that Longisquama is somehow "pre-feathers". If it is
instead an early example of having feathers, just
feathers slightly different than we know them from
their barbs being joined at the leading and trailing
edges, all the "radial symmetry" and such could
still precede that stage evolutionarily, and indeed,
the radial symmetry would have had to, because the
joined barb tips would have made no sense for a
radially symmetric feather (now you've got a tube
full of radial fibers with a rib up the middle of
the tube, not much good for anything but being a
cat-tail seed head).
Like I said, for many reasons in the physical
evidence, what Longisquama has doesn't work to be
membranes as the debunkers claimed, I'm just trying
to find ways to allow for that concept and
Longisquama still to be in the pathway on the way to
feathers. If radially symmetric feathers evolved to
bilaterally symmetric ones, part of that change
_might_ have rejoined the barbs into a "membrane", I
just don't buy it in the Longisquama photos.
>>>>http://www-hsc.usc.edu/~cmchuong/nature.pdf
"New uses" then. The follicle being itself a pretty
obvious evolved feature, having its own evolved
local chemical balance isn't much of a reach, we
know all about the modern ontogeny control chemicals
that make such stuff happen.
xanthian.
Sorry this reads so confused, do your best to read
it with a bit of forgiveness. I'm a bit sleep
deprived tonight, with only about 30 minutes of lie
down time in the last 36 hours or so. Too much new
art has been created on my computer recently, mostly
1280x800 screen wallpapers in abstract art style,
plus the WOWIO.com (USA only) "free books" site is
giving me five free books a day, more than I can
possibly read with all the rest of the stuff I do.
JTEM
> Just because you lack the ability to distinguish
> between drivel and science doesn't mean the
> _intelligent_ people here do.
You've confused "observation" for dribble and "knee-jerk"
for science.
Thse things are more so "bird tracks" than those things
associated with Longisquama are "feathers."
Now, why don't you go back to blowing smoke...
Kent Paul Dolan
> Thse(sic) things are more so "bird tracks" than those things
> associated with Longisquama are "feathers."
Apparently you cannot even read with understanding
the articles you URL -- the scientists themselves say
that it is too early to classify those tracks as confirmed
bird tracks...
> Now, why don't you go back to blowing smoke...
...that would be you, claiming that documents you URL
say what even the involved researchers disclaim them
saying.
Do have a nice, idiot-appropriate day of heavy drooling.
Quantum valeat.
xanthian.
JTEM
> Apparently you cannot even read with understanding
> the articles you URL -- the scientists themselves say
> that it is too early to classify those tracks as confirmed
> bird tracks...
While they most definitely *Are* tracks, or at least there
has yet to be any dispute on that much....
Your Longisquama cite? Well, there have been those who
dispute the very notion of feathers.... plenty of people...
Augray
wrote in <1176971331.1...@y5g2000hsa.googlegroups.com> :
Apparently, this is not what the authors see in Jones et al.
>If instead it is a (single thickness, by the logic I
>explained earlier) membrane which collided to form a
>rachis just as barbs in feather follicles do today,
>there's nothing to prevent the aptosis that turned
>the membrane into barbs from evolving later in time,
>and what are now barbs and rachis being
>interconvertable.
Well, no. The authors argue that barbs are primitive. Also, note that
none of the experiments resulted in a membrane.
>Remember, in current feathers, the
>rachis isn't a real separate thing, it is just the
>bases of a bunch of barbs that collided and merged
>together.
Which would discount modern feathers arising from a membranous
precursor.
>There's not that much difficulty in the membrane
>coming from a follicle much smaller circumferance
>than the membrane's width. Plant leaves do the same
>trick everywhere today, by growing as two rolled
>surfaces with a central rib, which unfurls as it
>emerges from its narrow bud.
Plant leaves don't do the same thing at all, since they are still
alive and growing when they "unfurl". Feathers, on the other hand, are
mostly non-living keratin once they leave the follicle, and so must be
at their final size when they leave.
>When the Longisquama
>purported membrane changed later in evolution to a
>phalanx of barbs, growing out, remember, base first,
>the growth base could have simplified from two
>spirals to one circle. We lack the soft tissue
>fossil samples in detail great enough to distinguish
>the cases.
I very much doubt such fossils will ever be found, because I doubt
that they ever existed.
>> In addition:
>
>>: Our data suggest that a radially symmetric
>>: feather is more primitive than the bilaterally
>>: symmetric feather in terms of molecular and
>>: developmental mechanisms, and may have been the
>>: prototype of feathers (Fig. 5c). Some fossilized
>>: primitive skin appendages on Sinornithosaurus
>>: also favour this model.
>
>> Since the appendages of Longisquama are already
>> bilaterally symmetrical, this argues against any
>> homology as well.
>
>Again, you're assuming the "membrane" interpretation
>of Longisquama's "integumentary appendages", but
>that's surely not what the photos in the original
>paper depict: those are barbs, not "corrugations".
I disagree. It seems very obvious to me that they're corrugations in a
membrane. This is especially obvious in figure 4 of Jones et al. where
part of the lower vane seems to drape over an underlying object, and
the corrugations disappear.
>>>> Besides, cell death allows the barbs to spread
>>>> out, thereby increasing the width of the
>>>> resulting feather.
>
>>>> If the feather was a continuous membrane, its
>>>> width would be equivalent to the circumference
>>>> of the follicle it grew from.
>
>>> Yes, but that could have been accomodated in
>>> evolution by the inner circumference of the
>>> follicle being convoluted rather than smooth,
>
>> I'll have to think on that.
>
>Much like the interior surface area of a lung is
>huge, of a charcoal briquette is enormous, making
>something convoluted enough gives it "fractal
>dimension", where lots of line can be squashed into
>very little area or lots of surface into very little
>volume.
Having thought on it, this scenario seems unlikely. Keratin, while
being flexible, resists being changed from its initial shape,
otherwise the hooklets on the barbules would be rather useless. If the
circumference of the follicle was convoluted, the resulting membrane
would be too.
However, such an arrangement would make them relatively useless for
gliding.
>Anyway, I'm going to continue to contend that what
>Longisquama had was already highly evolved rachis
>and barb feathers, just with the outer tips of the
>barbs merged for reasons I explained in an earlier
>posting.
For gliding?
>The rest of this is just to try to make
>developmental peace with those who claim that's a
>membrane, by describing several ways it could have
>grown. Since we _do_ see follicles,
And as I pointed out before, this is by no means agreed upon.
>and we _do_ see
>the appendages,
Something that no one contests.
>we are at least guaranteed that
>whatever the character of the appendages, it was
>_somehow_ possible for them to grow from those
>follicles.
Well, they grew somehow. If they grew from follicles, they weren't
homologous with those of birds.
>>> Nature chose cell aptosis instead, but it isn't
>>> the only conceivable solution to getting wide
>>> feathers out of a narrow follicle.
>
>>> Notice also that your statement is in part an
>>> argument toward a refutation of the claims in
>
>>> http://www.erin.utoronto.ca/~w3reisz/pdf/Longis.pdf
>
>>> that what we are seeing in Longisquama's
>>> integumentary appendages is a membrane, for
>>> exactly the same reasons. The sheer developmental
>>> improbability of designing a follicle that would
>>> grow that appendage as two membranes plus a
>>> quill, [and therefore] in a figure eight
>>> cross-section, as that paper claims it to be, is
>>> a further argument against the claims in the
>>> above paper.
>
>> You assume that they grew from follicles, and this
>> is by no means agreed upon.
>
>Sure it is, the follicles are visible in the fossil,
>and that part of the "integumentary appendages" maps
>extremely well to the same parts of modern bird
>feathers. Look at the photo captions again.
There is no room for a dermal pulp in the appendages of Longisquama,
indicating that it's not homologous with avian feathers. Also note
that in figure 3, the tips of the supposed barbs are closer to the
animal than the bases, indicating a growth pattern completely opposite
to that of bird feathers.
>>>> There's also the problem of how a "membraneous"
>>>> feather could make the transition to a modern
>>>> feather and still perform its function in the
>>>> interim.
>
>>> That's a "problem", but it isn't a show stopping
>>> one, it's just one more question to which we
>>> don't yet have an answer. For one thing, we'd
>>> first have to know what the "function" was as a
>>> membranous feather. If it were for sexual
>>> display, the transition wouldn't be particularly
>>> challenging. If it were for trapping air against
>>> the body for insulation, the transition would
>>> improve the functioning.
>
>> How?
>
>The same way attic spun glass insulation has more
>insulating value than an equal weight per surface of
>the attic of a single sheet of plate glass. The
>trapped air acts as more insulation than the glass
>alone, and the more "fractal" the trapping agent,
>the more air gets trapped.
But if the glass is a continuous sheet, virtually *all* the air gets
trapped.
>>> You only have real problems that I can infer if
>>> the feather is in fact a flight feather in its
>>> membraneous form. That transition would be a
>>> tough one indeed.
>
>> So, if the appendages are indeed membranous, they
>> weren't used for flight?
>
>That isn't claimed for Longisquama anyway, the claim
>is that they may have been gliding appendages.
Which is basically what I meant.
>If
>so, membranes like those stretched between the legs
>or toes of many gliding species suffice just fine,
>so no, being membranous doesn't disqualify them from
>being instruments of flight.
However, there'd be no incentive to change to the current "style" of
feather, with barbs and barbules.
No, I'm merely pointing out that there are symmetrical feathers on
creatures more basal than Archaeopteryx, namely Caudipteryx and
Protarchaeopteryx.
>If it is
>instead an early example of having feathers, just
>feathers slightly different than we know them from
>their barbs being joined at the leading and trailing
>edges, all the "radial symmetry" and such could
>still precede that stage evolutionarily, and indeed,
>the radial symmetry would have had to, because the
>joined barb tips would have made no sense for a
>radially symmetric feather (now you've got a tube
>full of radial fibers with a rib up the middle of
>the tube, not much good for anything but being a
>cat-tail seed head).
Which makes one wonder why such a structure would evolve in the first
place.
>Like I said, for many reasons in the physical
>evidence, what Longisquama has doesn't work to be
>membranes as the debunkers claimed,
Unfortunately, that's what it seems to have had.
>I'm just trying
>to find ways to allow for that concept and
>Longisquama still to be in the pathway on the way to
>feathers.
Why?
>If radially symmetric feathers evolved to
>bilaterally symmetric ones, part of that change
>_might_ have rejoined the barbs into a "membrane", I
>just don't buy it in the Longisquama photos.
But why take such a circuitous route?
Kent Paul Dolan
>> Apparently you cannot even read with understanding
>> the articles you URL -- the scientists themselves say
>> that it is too early to classify those tracks as confirmed
>> bird tracks...
> While they most definitely *Are* tracks, or at least there
> has yet to be any dispute on that much....
So, that's what JTEM speak for "yes, I, JTEM, was lying,
pulling from my butt facts nowhere in evidence in the
URLs I provided" looks like? You need more practice at
admitting that you are a prevaricating fool.
> Your Longisquama cite? Well, there have been those who
> dispute the very notion of feathers.... plenty of people...
How sad for you that changing the subject doesn't in the
least distract from the evidence that you've once again been
caught with your pants around your ankles, lying for all the
world to see, lies archived in Usenet that can be pointed out
to others as cautionary examples that nothing you have to
say is ever worth a bit of believing.
xanthian.
Yes, Longisquama is very much in dispute as being feathered
or "something else"ed. Augray and I are having such a dispute
at this very time period. Since you have no habits useful for
the discussion of matters of science, you will undoubtedly
weigh right into that discussion, hauling your usual freight of
lies, misdirection, invincible ignorance, and abject stupidity.
Then I will commence kicking your butt around the block for
you, as here, as now, as everywhere, as ever.
JTEM
> So, [---nothing---]
*Yawn*
> > Your Longisquama cite? Well, there have been those who
> > dispute the very notion of feathers.... plenty of people...
>
> How sad for you that changing the subject
I wasn't changing the subject, you raging idiot. You have
demonstrated an inability to properly weigh evidence, and
I was presenting you with a clear-cut, unambigious example
where your trust in meager evidence fails miserably.
In reality (maybe you've heard of it), quite a bit of the evidence
is rather meager. You just don't notice because you're far too
busy typing paragraphs of lame insults that nobody will ever
read....