The so called Inca bone, also known as the preinterparietal bone, os Inca, Goethe's ossicle, and os ipactal is a triangular sutural bone located at the previous site of the posterior fontanelle. It is common and a normal variant. The Inca bone is one of the Wormian bones.
History and etymology
The Inca bone is so called because of the supposedly high incidence of Inca bones in Peruvian mummies .