The term semiannular sulcus refers to a superficial feature of the ventromedial cerebral cortex (CTX) in the human ( Mai-1997 ) and the macaque ( Dubach-2008 ). It is a cleft that defines the rostroventral boundary between the limbic lobe (LLB) and temporal lobe (TLB). Thus, it marks the boundary of the uncus, which is the surface of the most rostral parts of the amygdala (AMG) and hippocampal complex (HPC) ( Mai-1997 ). Updated 17 Dec 2024.