Question: function of three tiny bones in the ear

title: Middle ear
text: The structure of the middle ear in living amphibians varies considerably , and is often degenerate . In most frogs and toads , it is similar to that of reptiles , but in other amphibians , the middle ear cavity is often absent . In these cases , the stapes either is also missing or , in the absence of an eardrum , connects to the quadrate bone in the skull , although , it is presumed , it still has some ability to transmit vibrations to the inner ear . In many amphibians , there is also a second auditory ossicle , the operculum ( not to be confused with the structure of the same name in fishes ) . This is a flat , plate - like bone , overlying the fenestra ovalis , and connecting it either to the stapes or , via a special muscle , to the scapula . It is not found in any other vertebrates .