The structure indicated is the squamous suture
of the skull.
Sutures are junctions between the bones of the skull – they are a type of fibrous joint, bound together by Sharpey’s fibres
The squamous suture forms the joint of the skull between the squamous part of the temporal bone
and the inferior aspect of the parietal bone. Posteriorly, the squamous suture becomes the parietomastoid suture
where the mastoid process
articulates with the parietal bone
. Anteriorly, the squamous suture extends towards pterion
Learn more about the sutures of the skull
in this tutorial.