In reptiles, birds, and early fossil tetrapods, there is a single auditory ossicle, the columella which is homologous with the stapes, or "stirrup" of mammals. This is connected indirectly with the eardrum via a mostly cartilaginous extracolumella and medially to the inner-ear spaces via a widened footplate in the fenestra ovalis. The columella is an evolutionary derivative of the bone known as the hyomandibula in fish ancestors, a bone that supported the skull and braincase.
In reptiles, birds and early fossil tetrapods, .there is a single auditory ossicle, the columella which is homologous with the stapes, or "stirrup" of mammals. This is connected indirectly with the eardrum via a mostly cartilaginous extracolumel,la and medially to the inner-ear spaces via a widened footplate in the fenestra ovalis The columella is an evolutionary derivative of the bone known as the hyomandibula in fish ancestors, a bone that supported the skull and braincase.