The ossification of the membraneous part of the squamous occipital bone in man

The membranous part of the squamous occipital bone, above the highest nuchal line, develops from two pairs of centres and an occasional third pair, pre-interparietal, which may develop anterior to the interparietal centres. Previously it was considered that the pre-interparietal bone is found at the lambda, anterior to the interparietal, which is also a common site for the formation of sutural bones. In this study, on the basis of anomalies observed in a large series of skulls, sutural bones at the lambda are differentiated from the bone developed from the pre-interparietal centres. A separate pre-interparietal bone is identified by its shape and position. It is present behind the lambda within the territory of the membranous occipital bone.