In those ancient pullulating seas, the otolith hooked up with the swim bladder via a bone not unlike the ossicles linking our inner and outer hearing membranes. Finally the ensemble of bladder and otolith became, in certain species, a functioning ear, picking up and analyzing vibrations that the bladder received from mechanical motions of water outside the fish’s body.

George Michelsen Foy, Zero Decibels, loc. 341