Reshuffling or inventing prosomeres: Expensive radiation or expensive neural tissue?

The target article is an elegant synthesis of the developmental and functional data and views on the evolutionary origin of the mammalian isocortex, integrating results from cell and molecular biology, experimental neuroanatomy, and chemoarchitectonic studies. Complementarily, we give here an account of two modes of isocortical evolution (prosomere reshuffling and invention) in terms of costs of radiation and neural tissue.