No Brain Drain
Because the brain is soft tissue mostly made up of water, the fact that it was fossilized and did not dry out is a surprise to everyone. Such nice preservation likely occurred due to bacteria quickly mineralizing the brain tissue before decay ensued. It likely happened when the fish was suddenly buried during the Flood about 4,300 years ago.
* A. Pradel et al., “Skull and Brain of a 300-Million-Year-Old Chimaeroid Fish Revealed by Synchrotron Holotomography,” Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.0807047106.
http://www.answersingenesis.org/articles/am/v4/n3/brain-drain