The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline.
In the young skull, this area is rough and uneven, and is joined to the body of the sphenoid by a plate of cartilage.
By the twenty-fifth year, this cartilaginous plate is ossified, and the occipital and sphenoid form a continuous bone.
The upper surface, which constitutes the lower half of the clivus, presents a broad, shallow groove which inclines upward and forward from the foramen magnum; it supports the medulla oblongata, and near the margin of the foramen magnum gives attachment to the tectorial membrane
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