[2] The mandibular fossa is bounded, in front, by the articular tubercle; behind, by the tympanic part of the bone, which separates it from the external acoustic meatus; it is divided into two parts by a narrow slit, the petrotympanic fissure.

It opens just above and in front of the ring of bone into which the tympanic membrane is inserted; in this situation it is a mere slit about 2 mm.

[3] The contents of the fissure include communications of cranial nerve VII to the infratemporal fossa.

Petrotympanic fissure contains some of the fibers of the anterior ligament of malleus, which run on the base of skull and eventually attach onto the spine of sphenoid bone.

This article incorporates text in the public domain from page 140 of the 20th edition of Gray's Anatomy (1918)