SJ>Interesting, scientific journals take a few weeks to get out to
the
antipodes, but I saw the following brief report on the web at
http://www.nature.com/Nature2/serve?SID=5125902&CAT=TOC&PG=19980101 /
toc.html (you will have to sign on for a free subscription):
KK>I mentioned the two articles that appeared in Nature because
both mentioned "integumentary structures." The article,
"Feathers, filaments and theropod dinosaurs" it mentions
"Although few scientist have yet seen the fossil material, some are
already incorporating Sinosauropteryx into models for the origin of
feathers and bird flight."
In the article, An exceptionally well-preserved theropod dinosaur
from the yixian Formation of China" Feathers are not mentioned
until the "discussion" portion of the article. "The integumentary
structures are extremely interesting regardless of wether they are
referred to as feathers, protofeathers or some other structure."
In my opinion I think it is safe to say that this new fossil represents
co-evolution. Personally I equate this fossil to something similar to
bats, flying lemurs and flying squirrels. Like these animals
Sinosauropteryx may have evolved to fill an empty niche.
I don't think it discredits the evolution of birds from reptiles either. I
suppose one could use this fossil as a model as to how feathers
*might* of evolved. (I am not familiar to genetic studies comparing
scales and feathers. I learned something from this.)
I thought the second article, An exceptionally well-preserved
theropod dinosaur from the yixian Formation of China, was the
more interesting as it sought to only describe this new find and
then present ideas in the discussion portion.
Even in the discussion (I thought well written BTW) it mentioned "
. . . feathers, protofeathers, or some other structure." Indeed the
way these integumentary structures are described I thought of the
hollow shafted hairs that polar bears possess or hairs like those of
a hedgehog or, from Stephen's own continent, the hairs of an
Echidna.
I'm not implying that they are hairs or that Sinosauropteryx is
somehow related to mammals. I'm saying the integumentary
structures are similar to those I mention above. From these
observations I can say that the filamentous structures do not
necessarily have to be protofeathers but rather an adaptation of
some sort.
-snip-
KK>We found it interesting that the "artifacts of preservation"
appear
>only on the back, tail and belly. These are places where one
>would assume feathers, hairs or some kind of filamentous
structure
>would appear.
SJ>Reptiles did not have "hair"-that is one of the defining
characteristics of mammals. And I would have thought that
"feathers
would appear on the proto-bird's forelimbs!
KK> If one assumes that this is a "proto-bird" that *flew* and not a
prehistoric example of something like a Kiwi then I agree it would
be strange not to have "feathers" on the wings.
SJ>Even if this dinosaur turns out to have feathers, that will not
mean
we are one iota closer to understanding how they were developed
from
a reptile scale by a Darwinian, step-by-step, process.
KK> I agree.
-Major snipage of some interesting stuff-
KK>Does anyone know how or what produces artifacts of
>preservation? Why don't these artifacts of preservation appear
>around the open mouth, in between toes, around legs or under
the
>chin?
SJ>When things fossilise, skin and bone is replaced by minerals. I
presume this process can sometimes cause its own side-effects
(eg.
cracking of mud, etc). Also, I have heard that when one dies,
ones
fingernails and hair keep growing for a while. In the case of a
reptile, a possibility is that the scales might keep growing after it
has died and been covered by mud. Alternatively, the scales
might
flake off. Any of these possibilities might look like feathers.
Recently there was a report of another "feathered" dinosaur which
turned out not to be.
KK> This was the original question and intent of my post. I
probably didn't phrase it correctly. What I am curious about is why
are these structures considered artifacts of preservation. The
above is the best explanation I have read so far but, I have
misgivings about it too.
Indeed I too have heard about certain parts of the morphology
continuing to grow after death. If this is true and the integumentary
structures did grow after death then why do we not see these
artifacts around the beak or toenails?
It is also possible that the scales could flake off but, I don't see
how this explains it either. If they did flake off the scales show us
their morphology; - filamentous-. Modern reptiles do shed and if we
are to use this as an example then there should be larger portions
connected together and not individual scales.
SJ> "When things fossilise, skin and bone is replaced by minerals.
I
presume this process can sometimes cause its own side-effects
(eg. cracking of mud, etc). "
KK> Is there a geologist in the house! :-)
Kevin