The
ectotympanic, or
tympanicum, is a bony structure found in all
mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In
catarrhine primates (including humans), it takes a tube-shape.
Its position and attachment to the
skull vary between
primates, and can be either inside or outside the
auditory bulla.
It is homologous with the angular bone of non-mammalian tetrapods. When the latter is present, it contacts the entotympanic.
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