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-Press Release Number: PR-ESRF-09-2-45B
-Source: European Synchrotron Radiation Facility
-Date issued: March 2, 2009
-Contact: Montserrat Capellas Espuny, +33 476 88 26 63, press@esrf.fr Scientists discover the first fossil brain A 300-million-year-old brain of a relative of sharks and ratfish has been revealed by French and American scientists using synchrotron holotomography at the European Synchrotron Radiation Facility (ESRF). It is the first time that the soft tissue of such an old fossil brain has ever been found. The results are published in PNAS this week.  As in many scientific discoveries, it all happened by chance. The team from the National Natural History Museum in Paris (MNHN in French), the ESRF and the American Museum of Natural History in New York was using the synchrotron to study one of the few skulls of an iniopterygian fish that has maintained its three dimensions (most of them are squashed). Inopterygians are an extinct relative of sharks and ratfish, and used to live on the shallow and muddy marine ground. They were not bigger than 50 centimeters.
Image 1. Image of the fossil. (Credit: PNAS)
The scientists used the technique of absorption microtomography to study different samples. One sample, stemming from Kansas (US), revealed a peculiar structure: it was denser than the surrounding matrix that fills the braincase, and which is made of crystalline calcite. In order to elucidate its structure in detail, they decided to use a second technique, X-ray holotomography. Surprisingly, the results showed a symmetrical and elongated object placed in the same position as a brain would have been. The 3D reconstruction showed different parts of the brain, such as the cerebellum, spinal cords or optic lobes and tracts, among others. The only part the researchers couldn’t spot was the forebrain, perhaps too thin to become mineralized.  Further analysis of the fossil indicated that the area where the brain-like structure reaches the surface of the sample reveals a high concentration of calcium phosphate, whereas the surrounding matrix is almost pure calcium carbonate. The mineralization of the brain is, according to the main author of the paper, Alan Pradel, from the MNHN, “due to the presence of bacteria that covered the brain shortly before decay and induced its phosphatization”.
Image 2. Superposition of the skull and the brain (inside) on the fish anatomy. (Credit: PNAS)
On top of this, the environmental conditions, probably saturated with calcium phosphate, the lack of oxygen in the braincase and the presence of fatty acids in the brain may have generated a fall in pH that also shifted the appearance of calcium carbonate in favour of calcium phosphate.  Scientists already knew that iniopterygians must have possessed a brain, but this new discovery can shed light on brain evolution during major evolutionary transitions, provided that other similar cases of exceptional preservation turn up in key fossils. This research also proves that, thanks to the use of microtomographic techniques in lightsources like the ESRF, details of the anatomical organisation of the nervous system in fossil brains are, from now on, potentially available.
Image 3. The structure of the skull (foreground) of a 300-million-year-old iniopterygian fish from Kansas remotely related to living ratfish is elucidated thanks to holotomography, a technique based on synchrotron X-ray phase contrast imaging (background), and yields the first hint at an exceptional mineralization of the brain (orange). (Credit: PNAS/Philippe Janvier (CNRS, Museum National d'Histoire Naturelle)
### Reference: Pradel, A., et al, Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography, PNAS Early Edition, 2 March Movies:
http://www.esrf.fr/files/press/Braincase_lat.mov
Movie of the 3D reconstruction of the braincase (green), the endocranial cavity (red) and the brain (orange) in lateral view. http://www.esrf.fr/files/press/brain_lat.mov
Movie of the 3D reconstruction of detail of the posterior part of the orbit with the brain in a better resolution (from Holotomography imaging) in lateral view (purple: braincase, blue: endocranial cavity, orange: brain). http://www.esrf.fr/files/press/brain_dorsal.mov
Movie of the 3D reconstruction of detail of the posterior part of the orbit with the brain in a better resolution (from Holotomography imaging) in lateral view (purple: braincase, blue: endocranial cavity, orange: brain). All movies courtesy of PNAS.
Also: Oldest fossil brain found in Kansas and imaged in France [Note: Published in Proceedings of the National Academy of Sciences of the USA, online before print March 9, 2009, doi: 10.1073/pnas.0807047106; Alan Pradel, Max Langer, John G. Maisey, Didier Geffard-Kuriyama, Peter Cloetens, Philippe Janvier, and Paul Tafforeau; "Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography". X-ray data collection took place at the European Synchrotron Radiation Facility, beamline ID-19. The contents of all materials on lightsources.org are the sole responsibility of the authors of the materials and/or the facilities or institutions under whose auspices the materials were produced. -lightsources.org]
Tags:
Archaeology and Forensic Science
ESRF - European Synchrotron Radiation Facility
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