In newborns, X-rays readily distinguish hypophosphatasia from osteogenesis imperfecta and congenital dwarfism. Some stillborn skeletons show almost no mineralization; others have marked undermineralization and severe rachitic changes. Occasionally there can be peculiar complete or partial absence of ossification in one or more vertebrae. In the skull, individual membranous bones may calcify only at their centers, making it appear that areas of the unossified calvarium have cranial sutures that are widely separated when, in fact, they are functionally closed. Small protrusions (or "tongues") of radiolucency often extend from the metaphyses into the bone shaft.