Smithsonian’s blog has a post about fossilized brains.  The brains belonged to a Cambrian arthropod called Fuxianhuia protensa from the famous Chenjiang fossil beds in south western China.  The paper appeared in the journal Cell Current Biology.  Interestingly, this study was a follow up to a paper that appeared in Nature in October of 2012.  In that instance, a single specimen of Fuxianhuia with preserved brain and optic nerves was described.  At that time, the preservation was thought to be implausibly rare.  However, the new paper details seven more specimens with similar preservation.  The complexity of these preserved brains, similar to modern day insects, is causing scientists to rethink early arthropod evolution.