Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.
The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies.
CR2P, UMR 7207 CNRS, MNHN, UPMC, Paris, France ; IPANEMA, USR 3461 CNRS, MCC, Gif-sur-Yvette, France.
Pierre
P
Gueriau
Synchrotron SOLEIL, Gif-sur-Yvette, France.
Cristian
C
Mocuta
15 passage du Buisson Saint-Louis, Paris, France.
Didier B
DB
Dutheil
IPANEMA, USR 3461 CNRS, MCC, Gif-sur-Yvette, France.
Serge X
SX
Cohen
Synchrotron SOLEIL, Gif-sur-Yvette, France.
Dominique
D
Thiaudière
CR2P, UMR 7207 CNRS, MNHN, UPMC, Paris, France.
Sylvain
S
Charbonnier
CR2P, UMR 7207 CNRS, MNHN, UPMC, Paris, France.
Gaël
G
Clément
IPANEMA, USR 3461 CNRS, MCC, Gif-sur-Yvette, France ; Synchrotron SOLEIL, Gif-sur-Yvette, France.
Loïc
L
Bertrand
D000818:Animals; D005399:Fishes / Q000033:anatomy & histology*; D005580:Fossils; D008674:Metals, Rare Earth / Q000737:chemistry*; D010163:Paleontology; D033561:Penaeidae / Q000033:anatomy & histology*; D013052:Spectrometry, X-Ray Emission / Q000295:instrumentation / Q000379:methods*; D017356:Synchrotrons
D008674:Metals, Rare Earth