Final answer:
True, tuataras do not have an external tympanic eardrum as their ear structure is different from mammals, which include three small middle ear bones - the malleus, incus, and stapes, for transmitting sound.
Step-by-step explanation:
It is true that tuataras do not have an external tympanic eardrum. In mammals, the reception of sound involves the pinna collecting sound waves, which then travel through the auditory canal to vibrate the tympanic membrane (eardrum). The vibrations are transferred via the ossicles, which are three small bones inside the middle ear, to the inner ear. These ossicles include the malleus (hammer), incus (anvil), and stapes (stirrup). Without these, primarily the malleus and incus, vibrations would not reach the ear's interior sufficiently. However, tuataras, which are reptiles, have a different ear structure and lack this external eardrum feature.