**Core Concept**
Körner's septum is a thin, fibrous plate that separates the middle cranial fossa from the petrous apex. It is a crucial anatomical landmark in neurosurgery and otolaryngology. The petrosquamous suture is a fibrous joint between the petrous part and the squamous part of the temporal bone.

**Why the Correct Answer is Right**
Körner's septum is located at the petrosquamous suture, which is a fibrous joint between the petrous part and the squamous part of the temporal bone. As the petrous and squamous parts of the temporal bone grow, they do not fuse completely, resulting in a fibrous joint. This joint is where Körner's septum is found, acting as a dividing plate between the middle cranial fossa and the petrous apex. The petrosquamous suture is significant in neurosurgery as it can be a point of entry for surgical procedures, and Körner's septum helps surgeons navigate this area safely.

**Why Each Wrong Option is Incorrect**
**Option B:** Temporosquamous suture is incorrect because it refers to the fibrous joint between the squamous part of the temporal bone and the parietal bone, not the petrous part. Körner's septum is not found at this suture.
**Option C:** Petromastoid suture is incorrect because it refers to the fibrous joint between the petrous part of the temporal bone and the mastoid part of the temporal bone. Körner's septum is not located at this suture.
**Option D:** Frontozygomatic suture is incorrect because it refers to the fibrous joint between the frontal bone and the zygomatic bone. Körner's septum is not found at this suture.

**Clinical Pearl / High-Yield Fact**
It is essential for neurosurgeons and otolaryngologists to be aware of Körner's septum's location at the petrosquamous suture to avoid complications during surgical procedures.

**✓ Correct Answer: A. Petrosquamous suture**