Abnormality of cranial sutures Accessory cranial suture 2014-05-25T10:54:52Z Supernumary fontanelle Accessory fontanelle UMLS:C4022927 The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centers. Accessory sutures can be explained on the basis of incomplete union of the two separate ossification centers. Accessory sutures usually will show a zigzag pattern with interdigitations and sclerotic borders similar to major calvarial sutures. A cranial suture that is in addition to canonical membrane-covered openings in the incompletely ossified skull of the fetus or newborn infant. Supernumary cranial suture Extra cranial suture Extra fontanelle UMLS:C4021067 HP:0012800