What is the name of the small bone at the base of our brain?

Question

studies have reveiled that hominids have this bone outher mamals do not.

Answer 1

You mean occipital bone? yet all mamals have it

Answer 2

Are you talking about the hyoid bone?  It's in the throat, not in the base of the brain.  Some studies have looked at the hyoid in Neanderthals to determine whether they were capapble of human-like speech.

Other than that, you must be talking about the first cervical vertebra (or Atlas).  The position of the foramen magnum (big hole) of the occipital bone can show that the vertebrae were directly under the head, which is an indicator of bipedalism.