FIGURE 10.

Comparison between neonate and adult dolphins, and between dolphins and terrestrial mammals. Different features converge to confirm the advanced developmental stage of the dolphin nervous system at birth. (A) Neuroanatomical features: (A’), neonatal/juvenile dolphin brain anatomy is very similar to that described in adults; (A”) white matter growth and myelination in dolphins are already advanced at neonatal/juvenile stages; WM, white matter; GM, gray matter; in the graph on the right the means calculated at single brain levels of different animals are showed. (B) Existence/exhaustion of postnatal germinal layers; (B’), advanced development of the cerebellar cortex in neo/postnatal dolphins: the external germinal layer (EGL) is extremely thin at birth and disappears at a very juvenile stage; the granule cell layer (IGL) is almost formed at birth; (B”) no germinal layer is detectable along the wall of the lateral ventricle at birth in dolphins, whereas it is present in all mammals studied so far (see references in the text). (C) The neonatal brain: comparison between aquatic and terrestrial mammals.