A
suture is a type of
fibrous joint which only occurs in the
skull (or "cranium"). The bones are bound together by
Sharpey's fibres. A tiny amount of movement is permitted at sutures, which contributes to the
compliance and
elasticity of the skull. These joints are
synarthroses. It is normal for many of the bones of the skull to remain unfused at birth. The fusion of the skull's bones at birth is known as
craniosynostosis. The term "
fontanelle" is used to describe the resulting "soft spots". The relative positions of the bones continue to change during the life of the adult (though less rapidly), which can provide useful information in
forensics and
archaeology. In old age, cranial sutures may ossify (turn to bone) completely.