epipteric

from The Century Dictionary.

• Situated over the alisphenoid or greater wing of the sphenoid bone: specifically applied, in human anatomy, to a supernumerary or epactal bone of the skull sometimes found in the fontanel at the anterior inferior angle of the parietal bone, just above the end of the alisphenoid.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Pertaining to a small Wormian bone sometimes present in the human skull between the parietal and the great wing of the sphenoid.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Of or pertaining to supernumerary bones (Wormian bones) occasionally present in the pterion region of the human skull.
• noun anatomy A bone of this kind.