We recently discovered new well 3D-preserved jawed vertebrates in two Paleozoic (540-240 Ma) deposits, one in Uruguay, the other in Peru. Exceptionally, in addition to some muscles associated to the head, we found a mineralized brain in a cartilaginous fish (sharks, rays and chimaeras) and probably in a stem jawed vertebrate placoderm. Only two previous cases of vertebrate fossilized brains were documented to this date, and these new remarkable preservations of species that lived during an important evolutionary radiation of modern jawed vertebrates will provide new characters documenting the early stages of the still debated morphological evolution of the vertebrate head and central nervous system