Brain of the most ancient vertebrates (Agnatha: Heterostraci) and man: Comparison and inferences

Natural brain casts of Devonian heterostracans (Agnatha: Heterostraci) are compared for the first time with the brain of contemporary man. The similarity in telencephalon morphology is revealed; the olfactory brain part of both man and heterostracans contains the olfactory tracts and bulbs. Based on the similarity in the olfactory apparatus of adult heterostracans and gnathostomes (sharks) it is concluded that the developmental schemes of the hypophysis, which adjoins the diencephalon, are similar in these groups. In the evolution of vertebrates, Diplorhina (Agnatha having two nostrils) and jawed vertebrates (Gnathostomata) form a natural phylogenetic branch, in which Diplorhina and man are regarded as the lowest and most advanced morphological levels.