Final answer:
Both prosimians and anthropoids have a mandible that is initially in two halves; these fuse into a single bone during the first year of life in both groups.
Step-by-step explanation:
The question deals with the anatomical structure of the mandible in different primates. Both prosimians and anthropoids have a mandible that, at the time of birth, consists of two halves. These halves fuse together during the first year of life to form a single U-shaped mandible. This process occurs in all primates, including prosimians such as lemurs, lorises, and tarsiers, as well as anthropoids like monkeys, apes, and humans. The fusion of the mandible provides a solid and robust structure that supports the teeth and muscles involved in feeding and vocalization.