Final answer:
Mummification typically occurs in the head and neck of a decedent's body, especially in a dry environment.
Step-by-step explanation:
In the process of mummification, the decedent's body typically undergoes the most significant preservation in the head and neck region, especially if the decedent is found in a dry environment. This is because the head and neck area contains less soft tissues and is more resistant to decomposition. Additionally, the brain is often removed from the skull during mummification, further aiding in the preservation of the head.