The frontal suture is a dense connective tissue structure that divides the two halves of the frontal bone of the skull in infants and children. It usually disappears by the age of six, with the two halves of the frontal bone being fused together. It is also called metopic suture, although this term may also refer specifically to a persistent frontal suture (further detailed in section below).
If the suture is not present at birth because both frontal bones have fused (craniosynostosis), it will cause a keel-shaped deformity of the skull called "trigonocephaly."
It is present in a fetal skull so that the skull can bend and is very elastic at the time of birth. The baby's head bends when coming out of the mother's womb. The space is filled as the child grows older.
Read more about Frontal Suture: Persistent Frontal Suture