The term arcuate sulcus refers to a composite superficial feature of the frontal lobe of the macaque. Located on the dorsolateral surface, it consists of the superior limb of the arcuate sulcus, the inferior ramus of the arcuate sulcus and the spur of the arcuate sulcus ( Krieg-1975; Walker-1940 ). The adult human has no feature topologically equivalent to the arcuate sulcus of the macaque ( Matelli-2004 ). One finds a similar angular depression, however, in the human-fetal-brain.htm" TARGET="_BLANK">fetal cortex of the 32-33 week human. There the vertical, inferior limb appears to become the inferior precentral sulcus. The depression located rostral to it in the 32-33 week human fetus, a location comparable to that of the principal sulcus, appears to become the inferior frontal sulcus instead ( Savel'ev-2005 ). And, based upon the organization of human-motor-cortex.htm" TARGET="_BLANK">architectonic areas relative to sulcal features, the superior, horizontal component appears similar in location to the superior frontal sulcus and superior precentral sulcus. Equivalent structures are not found in the smooth cerebral cortex of the rat or mouse ( NeuroNames ).