Inferior view of disarticulated sphenoid, temporal, and occipital bones. The unpaired sphenoid bone and its greater wings contain the foramen ovale and foramen spinosum that are located on the roof of the infratemporal fossa. The pterygoid processes consisting of lateral and medial pterygoid plates project inferiorly. This view of the temporal bone reveals the mandibular fossa for articulation with the condyle of the mandible, the root of the zygomatic arch and zygomatic process, the mastoid process, and petrous portion of this bone. The petrous part contains the opening of the carotid canal for the internal carotid artery and is located just anterior to the jugular foramen, a space between the petrous bone and occipital bone. The tympanomastoid fissure or suture separates the tympanic part of the temporal bone from the mastoid part and following this suture leads to the stylomastoid foramen for exit of the facial nerve. Medial to the mastoid process is the mastoid notch for attachment of the posterior digastric muscle. The unpaired occipital bone contains the large foramen magnum that is bordered anterolaterally by the occipital condyles for articulation with the atlas. On its posterior surface are a series of horizontal lines (nuchal lines) for attachment of muscles. The foramen lacerum is a space between the petrous apex, the greater wing of sphenoid and clivus. The petroclival fissure is a line of fusion between the petrous bone and clivus and contains the inferior petrosal sinus. (Image courtesy of AL Rhoton, Jr.)