Wormian bones

In addition to the usual centers of ossification of the cranium, others may occur, giving rise to irregular isolated bones termed sutural or Wormian bones. They occur most frequently in the course of the lambdoidal suture, but are occasionally seen at the fontanelles, especially the posterior. One, the pterion ossicle, sometimes exists between the sphenoidal angle of the parietal bone and the great wing of the sphenoid bone. They have a tendency to be more or less symmetrical on the two sides of the skull, and vary in size. Their number is generally limited to two or three; but more than a hundred have been found in the skull of an adult hydrocephalic subject.

Note: Ole Worm, Professor of Anatomy at Copenhagen, 1624–1639, was erroneously supposed to have given the first detailed description of these bones.