Final answer:
The joint that unites the parietal bones along the top of the skull is called the sagittal suture. It runs along the midline and is different from the coronal, lambdoid, and squamous sutures, which connect other skull bones.
Step-by-step explanation:
The joint that unites the parietal bones along the superior midline of the cranium is known as the sagittal suture. The parietal bones are paired bones that form the upper, lateral sides of the skull. The right and left parietal bones join together at this suture, which runs along the midline at the top of the skull, in the sagittal plane of section. It's important to differentiate this from the coronal suture, which runs across the skull and joins the frontal bone to the right and left parietal bones. Furthermore, the lambdoid suture unites the occipital bone to the parietal bones at the posterior part of the skull, and the squamous suture joins the parietal bone to the squamous portion of the temporal bone on the lateral side of the skull.