Chemical analysis has rarely been applied to vertebrate fossils; such as the exceptionally preserved 120 Mya Chinese bird Confuciusornis. Ideally such analysis would measure and map the chemistry of bone, soft tissue structures, and the embedding rock matrix.
analysis has rarely been applied to vertebrate fossils; such as the exceptionally preserved 120 Mya Chinese bird
Confuciusornis. Ideally such analysis
would measure and map the chemistry of bone, soft tissue structures, and the
embedding rock matrix. Mapping such a fossil in situ would place constraints on the mass transfer between embedding
matrix and the preserved specimen, and therefore aid in distinguishing
taphonomic processes from original chemical zonation remnant from the fossil itself.
Conventional nondestructive analytical methods face serious problems in this
case and most recent technological advances have been targeted at developing
nanometer-scale rather than decimeter-scale capabilities. However, the recent
development of Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) at the
Stanford Synchrotron Radiation Lightsource now allows large specimens to be
non-destructively analyzed and imaged using major, minor, and trace element
the identification of endogenous and exogenous phases.
High-resolution SRS-XRF maps show how an entire Confuciusornis specimen, along with large sections of the mudstone
matrix, can be chemically mapped (for Si, P, S, Cl, Ca, Ba, Mn, Fe, Zn, Cu, Br,
and Pb). The results from this work unequivocally show that the feathers in
this Confuciusornis are not simply
impressions. This technique has shown
that some trace metals (e.g., copper) correlate with discrete biological
structures in a range of extinct and extant organisms, most notably in feathers
of Confuciusornis. Additionally,
x-ray absorption spectroscopy shows that the chemical inventory of fossils
commonly consists of organo-metallic and organo-sulfur compounds coordinated in
a manner similar to extant organisms. The application of SRS-XRF imaging can
help identify and map the crucial elements associated with original soft
tissues. In the case of Confuciusornis
this evidence suggests that
copper can be used as a biomarker for the distribution of the darker eumelanin
pigment, providing the first accurate reconstruction of dark pigment patterns
across an entire extinct organism.
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