[show abstract][hide abstract] ABSTRACT: 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.