 Frogs and all other living tetrapods have a rod @-@ like bone called the stapes that aids in hearing by transferring vibrations from the ear drum — or homologous tympanum — to the inner ear . Temnospondyls also have a stapes , which projects into the otic cavity . The stapes likely evolved from the hyomandibula of lobe @-@ finned fishes . The positioning of the stapes and the shape of the otic region suggests that the tympani of temnospondyls and frogs are homologous , but the tympani of these amphibians are no longer considered homologous with the hearing systems of reptiles , birds , and mammals . Therefore , ear structures in temnospondyls were not ancestral to those of all other tetrapods . 
 Frogs and all other living tetrapods <a href='got' title='1'><mark>have</mark></a> a rod @-@ like bone called the stapes <a href='null_relcl' title='2'><mark>that</mark></a><a href='uninflect' title='3'><mark>aids</mark></a> in hearing by transferring vibrations from the ear drum — or homologous tympanum — to the inner ear . Temnospondyls also <a href='got' title='4'><mark>have</mark></a> a stapes , which <a href='uninflect' title='5'><mark>projects</mark></a> into the otic cavity . The stapes likely evolved from the hyomandibula of lobe @-@ finned fishes . The positioning of the stapes and the shape of the otic region <a href='uninflect' title='6'><mark>suggests</mark></a> that the tympani of temnospondyls and frogs are homologous , but the tympani of these amphibians are no longer considered homologous with the hearing systems of reptiles , birds , and mammals . Therefore , ear structures in temnospondyls <a href='negative_concord' title='7'><mark>were</mark></a> <a href='negative_concord' title='8'><mark>not</mark></a>ancestral to those of all other tetrapods . 
Frogs and alll other living tetrapods got a rod @-@ like bone called the stapes aid in hearin by transferring vibrations from da ear drum — or homologous tympanum — to the inner ear . Temnospondyls also got a stapes , which project into the otic cavity . The stapes likely evolved from the hyomandibula of lobe @-@ finned fishes . The positioning of the stapes and the shape of the otic region suggest that the tympani of temnospondyls and frogs r homologous , but the tympani of these amphibians ain't no longer considered homologous w tdahhearinsystems of reptiles , birds , and mammals . Therefore , ear structures in temnospondyls ain't ancestral to those ofallll other tetrapods .