There seem to be three major camps in this debate (at least). Those who map the morphology of both extant and extinct feathers to compare and contrast the presence, absence and shape of the biological paint-pots (melanosomes) that once might have held pigment (remember that an albino would have no pigment, but still have melanosomes). The second group of folks seem to favour chemistry, given it might well be possible to identify the remnant chemistry of pigments, locked in the degraded keratinous tissues of fossil feathers. The third group, looks at both structure and chemistry.
|Biological paint-pots or bacterial contamination, that is the question?|
|The eumelanin pigment molecule with its central copper atom.|
Group 2 have been using chemistry to aid in their interpretation of possible pigments preserved in fossil feathers. This is a powerful technique, if it is possible to constrain elements/compounds that are linked to, or are breakdown products of original pigments. Some chemical techniques can only map small areas of fossils and are often not sensitive enough to detect the dilute concentrations of trace-metals that might well be associated with pigments. The x-ray analysers (such as EDAX) on many ESEM's only allow a rough guide as to the presence or absence of elements and are often difficult (if not impossible) to map over large areas. The EDAX is also unable to constrain the oxidation state of elements, which is so critical to the elucidation of their organic or inorganic origins.
|ESEM and EDS can provide valuable information, but not to the same resolution or |
sensitivity of synchrotron based imaging.
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It is clear that the different groups are all generating new and exciting data. This is splendid. As more data gets published, more information becomes available to the wider scientific community. Hopefully within this growing sink of evidence, more robust hypotheses can be constructed as to the preservation of feathers and the possibility of a whiff of colour.