The term simian sulcus refers to the confluence of the intraparietal sulcus, the lunate sulcus of the human and the parieto-occipital sulcus on the dorsal surface of the cerebral cortex of the macaque ( Kappers-1960 ). It is an externally visible opening to the intraparietal sulcus, which some authors refer to as the 'simian fossa'. It is not identified as a separate structure in brain atlases of the human, and equivalent structures are not found in the smooth cerebral cortex of the rat or mouse ( NeuroNames ).