The first bone to show both endochondral and intramembranous ossification :

The cranial base will be in cartilaginous form till 7th week of prenatal form. After that, the bones of cranial base undergo both endochondral as well as intramembranous ossification. The first bone to show both endochondral and intra-membranous ossification is occipital bone. The supranuchal squamous part of occipital bone ossifies intramembranously during the 8th week of intra-uterine life.