Evolution of the Telencephalon in Anamniotes.
Résumé
The telencephalon is the most anterodorsal craniate/vertebrate brain division and forms with its anteroventral complement, the hypothalamus, the most rostral portion of the neural tube. The telencephalon represents part of the ancestral craniate (and, thus, anamniote) brain Bauplan (morphotype). The craniate telencephalon includes ventrally a subpallial region (medially: septum; laterally: striatum) and dorsally a pallial region. In addition to olfactory bulb input, the pallium receives ascending sensory information in all craniates, with largely separate pallial terminations in all jawed vertebrates (gnathostomes). While it is likely that a lateral pallium (olfactory cortex homologue) and a medial pallium (hippocampus homologue) arose at the latest with the gnathostomes (and likely are ancestral for craniates), a dorsal pallium may have arisen several times independently in chondrichthyans, teleosts and amniotes. A separate pallidal subdivision of the craniate striatal formation may only have evolved with the gnathostomes.