Carl,
In this case we must use comparative anatomy (or comparative histology). We must check also the symmetry (if any bilaterality or radiality is aplicable) of the colour pattern.
Also is truth that some colour patterns are, in fact, the signature of some anatomical structure but not coloration. For example in some arthopods, it is comming to my mind the cranidium of Ectillaenus -Trilobita- where you can find muscle attachment scars. As the scars show a distictive not smoth surface, they sometimes shows two different colour in the fossils -presumibly not in the living animal-, iridiscent and pigmented by oxides (in the fossil!). Both are fairly common examples in the middle ordovician from Spain. However, from comparative anatomy we know that these spots are, in fact, muscle attachment. In contrast, spots or bands in moth's wings should be coloration patterns.
Patricio
----- Mensaje original -----
De: Carl Mehling <cosm@amnh.org>
Fecha: Martes, Junio 14, 2005 10:02 pm
Asunto: Re: paleonet Fossil Color
> That brings me to another question I've had about color patterns:
> how sure
> can we be that these patterns were part of the external coloration
> of the
> living organism rather than an alteration of some aspect of the
> structure
> of the tissues that manifests diagentically as a visible pattern?
>
> -Carl
>
> At 02:03 PM 6/14/2005, you wrote:
>
> >Carl, I am not sure. Probably it is just an aproximation.
> However, I
> >belive that the proper colour is rather an "artistic"
> interpretation.
> >Actually, the important thing is to discover patterns.
> >
> >They can show mimicry patters (disruptive), display
> >patterns... Iridiscent patterns can works also with UV light
> (i.e. in the
> >checks of parakeets). If we are able to survey the surfaces of
> the fossils
> >we could find these kind of changes. But the real colours... that
> it's
> >another problem.
> >
> >Patricio
> >
> >----- Mensaje original -----
> >
> >De: Carl Mehling <cosm@amnh.org>
> >
> >Fecha: Martes, Junio 14, 2005 7:15 pm
> >
> >Asunto: Re: paleonet Fossil Color
> >
> > > Damn...
> > >
> > > That said, since iridescence is structural, can the original color
> > > be
> > > determined from an analysis of the preserved structure?
> > >
> > > -Carl
> > >
> > > At 12:21 PM 6/14/2005, you wrote:
> > >
> > > >Carl,
> > > >
> > > >That is correct. After burial the proportions of the micro-
> > > surfaces
> > > >change. We are talking in terms of light wavelenght (700
> > > nanometers for
> > > >red 400 nm for blue). Just some little deformation (some
> > > nanometers in
> > > >that particular surface) is enough to change these physical
> > > properties.
> > > >We can see the color pattern but not the former factual colour.
> > > >
> > > >
> > > >
> > > >Patricio
> > > >
> > > >----- Mensaje original -----
> > > >
> > > >De: Carl Mehling <cosm@amnh.org>
> > > >
> > > >Fecha: Martes, Junio 14, 2005 6:03 pm
> > > >
> > > >Asunto: Re: paleonet Fossil Color
> > > >
> > > > > Thanks Patricio. I was aware of the difference between
> pigment vs.
> > > > > structural color. But not to the degree you outlined -
> thanks! One
> > > > > question: When you say of the Messel beetles "could be not
> green> > > > but dark
> > > > > violoaceous" do you mean that the colors they show are not
> > > > > original or may
> > > > > not be original?
> > > > >
> > > > > -Carl
> > > > >
> > > > > At 11:48 AM 6/14/2005, you wrote:
> > > > >
> > > > > >Living organisms exhibit two main types of coloration:
> pigmentary> > > > and
> > > > > >structural colours. Probably you realise what is a pigmentary
> > > > > color. A
> > > > > >pigment, usually an organic component such as melanins (i.e.
> > > > > mammal’s skin
> > > > > >and hair), carotenoids (i.e. astaxanthin in crayfish), bilins
> > > > > (i.e.
> > > > > >bilverdin in bird eggs), quinines (i.e. echinoquinones in sea
> > > > > urchins),
> > > > > >give some coloration as ink do it in a paper. Usually such
> > > > > pigments are in
> > > > > >specific cells (chromatophores, melanophores, etc)
> scattered in
> > > > > particular
> > > > > >tissues (dermis, epidermis, etc.).<?xml:namespace prefix
> = o
> > > ns =
> > > > > >"urn:schemas-microsoft-com:office:office" />
> > > > > >
> > > > > >On the other hand, structural colours are due to the
> microscopic> > > > features
> > > > > >of the physical surfaces. These include interference,
> > > > > diffraction,
> > > > > >reflection, refraction, iridescence… A very famous structural
> > > > > colour is
> > > > > >the Tyndall blue (a similar phenomena to the Rayleigh
> scattering> > > > observed
> > > > > >in Earth’s atmosphere). Nacre exhibits iridescent structural
> > > colour.> > >
> > > > > >Animals combine any of such structural colours with pigments
> > > in a
> > > > > plethora
> > > > > >of visual effects not only in the same estructure but also
> > > > > different parts
> > > > > >of the organism are coloured using differnt "technologies".
> > > > > Usually,
> > > > > >black or brownish colours are usually pigmentaries. However,
> > > > > white colour
> > > > > >rarely is pygmentary .
> > > > > >
> > > > > >Most of the pigments may well decay after death. However
> > > > > structural
> > > > > >colours may be easily preserved, although as such colours
> depends> > > > of the
> > > > > >very precise length of the micro-details of the surface
> (in terms
> > > > > of
> > > > > >fraction of wavelength of incident light) the resulting
> colour> > > > after
> > > > > >fossilization should be very different. For example, the
> > > > > beautiful
> > > > > >metallic green of some of the Lucanids beetles from
> Messel, could
> > > > > be not
> > > > > >green but dark violoaceous (for example). Other examples of
> > > > > structural
> > > > > >coloration are the brownish pattern that some fossil
> moths and
> > > > > butterflies
> > > > > >exhibit in their wings.
> > > > > >
> > > > > >
> > > > > >
> > > > > >Jere Lipps proposes a couple of Ph.D. dissertation on
> colours.> > > > Possible
> > > > > >candidates: don’t forget to use SEM to check the
> surfaces at
> > > > > wave length
> > > > > >scale. Structural colours, although not visible today
> should be
> > > > > preserved
> > > > > >in some way…
> > > > > >
> > > > > >
> > > > > >
> > > > > >Cheers,
> > > > > >
> > > > > >
> > > > > >
> > > > > >Patricio Domínguez
> > > > > >
> > > > > >
> > > > > >
> > > > > >----- Mensaje original -----
> > > > > >
> > > > > >De: "Jere H. Lipps" <jlipps@berkeley.edu>
> > > > > >
> > > > > >Fecha: Martes, Junio 14, 2005 8:23 am
> > > > > >
> > > > > >Asunto: Re: paleonet Fossil Color
> > > > > >
> > > > > > > We need some studies on the taphonomy of color.
> > > > > > >
> > > > > > > My impression is that color is preserved in certain
> > > circumstances,> > > > including species-specific aspects.
> > > Organic rich and/or anoxic
> > > > > > > deposits seem to preserve color sometimes, whereas others
> > > (oxic?)> > > > do not. Certain gastropods seem to show more
> > > color whereas
> > > > > > > others have no color when alive. So a taphonomic review
> > > would run
> > > > > > > the entire gamut from living through fossilization to
> > > collection> > > > by paleontologists (do we pick out the colored
> > > ones more than
> > > > > > > others?).
> > > > > > > Probably a couple of Ph.D dissertations in this, at least.
> > > Maybe
> > > > > > > some have been done, but more could be done I'd bet.
> > > > > > >
> > > > > > > Jere
> > > > >
> > > > > Carl Mehling
> > > > > Fossil Amphibian, Reptile, and Bird Collections
> > > > > Division of Paleontology
> > > > > American Museum of Natural History
> > > > > Central Park West @79th Street
> > > > > New York, NY 10024
> > > > > (212) 769-5849
> > > > > Fax: (212) 769-5842
> > > > > cosm@amnh.org
> > > > >
> > >
> > > Carl Mehling
> > > Fossil Amphibian, Reptile, and Bird Collections
> > > Division of Paleontology
> > > American Museum of Natural History
> > > Central Park West @79th Street
> > > New York, NY 10024
> > > (212) 769-5849
> > > Fax: (212) 769-5842
> > > cosm@amnh.org
> > >
>
> Carl Mehling
> Fossil Amphibian, Reptile, and Bird Collections
> Division of Paleontology
> American Museum of Natural History
> Central Park West @79th Street
> New York, NY 10024
> (212) 769-5849
> Fax: (212) 769-5842
> cosm@amnh.org
>