fig 10. CT scans show progressive ossification of the orbitosphenoid (arrow) at 16 weeks 2 days, 17 weeks 4 days, 18 weeks 4 days, and 24 weeks 4 days. fig 11. CT scan of fetal specimen with a gestational age of 22 weeks 3 days shows ossification of alisphenoid (A), which forms the greater wing of the sphenoid. Foramen ovale and spinosum are seen as a large defect in the greater wing of the sphenoid (arrow)