Petrosquamous suture

The petrosquamous suture is a cranial suture between the petrous portion and the squama of the temporal bone that forms Koerner's septum. The petrous portion forms the medial component of the osseous margin, while the squama forms the lateral component. The anterolateral portion (squama) arises from the mesenchyme at 8 weeks of embryogenesis while the petromastoid portion develops later from a cartilaginous center at 6 months of fetal development.