A research team from the National Natural History Museum in Paris and the American Museum of Natural History in New York recently analyzed the 3D structure of a 300-million-year-old brain of a relative of sharks and ratfish at the European Synchrotron Radiation Facility (ESRF). This is the first time that the soft tissue of such an old fossil brain has ever been found, and the sample studied was found in Kansas, United Sates. The study was performed by combined use of absorption microtomography and a new holotomographic approach, which uses phase-contrasts. The analysis 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 might be due to the presence of bacteria that covered the brain shortly before decay and induced its phosphatization. For information about the holotomographic approach, see the paper, "Mixed transfer function and transport of intensity approach for phase retrieval in the Fresnel region", P. Guigay et al., Opt Lett., 32, 1617 (2007). For more information on this research, see the paper, "Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography", A. Pradela et al., Proceedings of National Academy of Science (published online before print March 9, 2009, doi: 10.1073/pnas.0807047106)
