tympanoperiotic

from The Century Dictionary.

• Including or consisting of a tympanic bone united with the periotic bone proper: used especially with reference to the ear-bone of cetaceans.
• noun A part of the skull of cetaceans, the so-called ear-bone of those animals, which consists of the periotic bones united with one another and with the tympanic, forming a single specially hard and durable bone readily detached from the rest of the skull.