(A, C) Mammalian species and orders (scientific name, common name – used hereafter – and abbreviation) with special reference to their brain size and lifespan (C, top). (B) Color code (see also Figure 4). (C, bottom), Different ages considered for each species; all groups are composed of four individuals (apart from different specification; Supplementary file 1). (D) Four anterior-posterior brain levels, identified by comparable neuroanatomy based on histology (example of a cat brain section in E), and correspondent mini-atlases for each animal species; representative sections within the thickness of each level are shown. (F) Paleocortex-neocortex transition (arrowheads), identified histologically as a shift from three to six cortical layers. Scale bars: E, 500 µm; F, 50 µm.