Topic summary
Periotic bone
Extracted from the Wikipedia article Petrosal bone.
The petrosal or petrosal bone, also known as the periotic bone or mastoid bone, is a bone of the skull that encloses the inner ear in mammals and their closest relatives. It is formed from a fusion of the prootic, the opisthotic, and possibly the epiotic; in humans, it is fused to the squamosal and the tympanic to form the temporal bone, of which it forms the petrous and mastoid portions.