ABSTRACT
The cranial base is derived from the primitive chondrocranium, and comprises the midline bones and the cranial fossae—anterior, middle and posterior—which in large part also originate in the chondrocranium, with additions, in certain bones, ossifying in membrane. In observing the earliest signs of ossification centers, one needs to be mindful of the features of ossification in long bones; indeed, in many respects the midline basicranial bones behave like long bones. The ascription of timing to the appearance of ossifie centers has been based either on estimates of fetal age, or on the length of the fetus. Bergland made a cross-sectional radiographic study of Norwegian and Lapp skulls. The sagittal depth of the bony nasopharynx showed little increase with age, since there was extension backwards of the nasal space represented by the posterior extension of the posterior nasal spine and of the dorsal border of the vomer. Measurements are collated by anthropometric techniques in the living or dry skulls.
