The hole at the base of a skull through which
the spinal cord passes. Literally, foramen
magnum means a "large hole or opening" in Latin. The position of the foramen
magnum is a strong indicator of the angle of the spinal column to the head
and subsequently whether the body is habitually horizontal (e.g., as in
the case of a horse) or vertical (e.g. as in the case of an ape or human).