Advanced cynodonts evolved even more mammalian modifications
of the skull.
Although the frontal bone changed little from the cynodonts to the first
mammals, three ancestral bones around the orbit were--the prefrontal,
postfrontal, and postorbital. In later cynodonts, the prefrontal and postorbital
bones were lost, and thus the postorbital bar which separated the orbit
and jaw musculature was lost. The alisphenoid moved closer to the basisphenoid.
Advanced cynodonts evolved tooth occlusion so that food could be ground
between matching surfaces of upper and lower teeth. They also developed
multirooted postcanine teeth.