- sphenoid fontanelle, sphenoid fontanel, sphenoidal fontanelle, sphenoidal fontanel - the irregularly shaped area on either side of the cranium where the frontal bone and the anterior tip of the parietal bone and the temporal bone and the greater wing of the sphenoid bone meet; corresponds to the pterion when bones have ossified
--1 is a kind of fontanelle, fontanel, soft spot