What is the definition or description of: fused skull bones?

Growth plates closed: The cranium or brain part of the skull is comprised of 8 different bones, and although these joints don't move like those in the extremities, there is slight movement which allows an infant's skull slight movement to enable birth and growth occurs at the margins to allow head symmetry. The margins or sutures generally fuse by 22-39 months. At times they can be prematurely closed and no longer.