The petrosquamous fissure, or suture, denotes the margins of the |petrous part| of the |temporal bone| and the |squamous part|. The |squamous part| is the ~anterior~ (forward) section, which comprises most of the glenoid |fossa|. The |petrous part| is the ~posterior~ (rearward) section, which forms the rear portion of the glenoid |fossa| and the frontal wall of the tympanum and |external auditory meatus|.