 The ability of the <unk> and <unk> to effectively transmit <unk> is called <unk> matching . Early <unk> like <unk> have thick <unk> with poor <unk> matching , so it is now thought that they were not used for hearing . Instead , these thick <unk> may have functioned to support the tissue that covers the <unk> notch . Early <unk> like <unk> could not hear airborne sound but would have been able to detect vibration in the ground . Later <unk> like <unk> had <unk> regions adapted to hearing . <unk> has a structure in the inner ear called the <unk> <unk> , which is also seen in frogs and is associated with hearing . Its <unk> is also a better <unk> of sound . The hearing system of <unk> and related <unk> was able to detect airborne sound and may have been ancestral to that of living amphibians . 
