The neocortex is a uniquely mammalian evolutionary innovation emerging within the dorsal pallium of the telencephalon - in early amniotes this region was the point at which the archicortex, paleocortex, and striatum converged.
The thalamus is the sole source of extrinsic non-olfactory input to the cerebral cortex but only five percent (5%) of the synaptic connections in the neocortex are of thalamocortical origin.
Olfactory input is via the paleocortex and proceeds directly to the olfactory centers of the neocortex.
In addition to the three layer allocortex of non-mammals, mammals possess an additional cortical component comprised of six layers.
.gif "Primary Somatosensory Cortex of the Owl Monkey")
