any structural anomaly of the dense, fibrous connective tissue joint between the frontal bones from the sagittal suture to the root of the nose; it is visible in neonates and juveniles, but it is frequently obliterated in some adult organisms; in mice and rats, the posterior frontal (PF) suture, situated between the frontal bones, is analogous to the human metopic suture; the anterior landmark for the PF suture is the jugum limitans; the posterior landmark for the PF suture is the bregma