Ossification starts as membranous ossification before birth. Myositis ossificans comprises two syndromes characterized by heterotopic ossification (calcification) of muscle. Resting zone, Proliferative zone, Hypertrophic cartilage zone, Calcified cartilage zone, Ossification zone. Premature complete ossification of these sutures is called craniosynostosis. Premature complete ossification of the sutures is called craniosynostosis. These bones are connected by hyaline cartilage and sometimes occur between ossification centers. These fractures occur at tubercles (bony projections that lack secondary ossification centers). This cartilage ultimately develops into new bone tissue through the process of endochondral ossification. Bone is resorbed by osteoclasts, and is deposited by osteoblasts in a process called ossification. The mesenchyme above the meninges undergoes intramembranous ossification forming the neurocranium. Heparin sulfate regulates signal transduction during chondrocyte differentiation, ossification, and apoptosis. Chondrostei are primarily cartilaginous fish showing some degree of ossification. The appendicular skeleton forms during development from cartilage, by the process of endochondral ossification. Intramembranous ossification, mediated by the periosteal layer of bone, occurs without formation of callus. The larger part of the scapula undergoes membranous ossification.