A sagittal crest is a ridge of bone that runs across the middle of the skull in apes like gorillas. Its purpose is to serve as a place of attachment for the the large muscles of the jaw. Human jaw muscles are attached at the temples. A high crown is not a sagittal crest. The creature in the Patterson film does not appear to have a sagittal crest in my opinion.
See: Wikipedia: Sagittal Crest , Sagittal Keel