The phylogeny of the middle ear ossicles

Abstract

Morphology of the ossicles tends to show adaptation to the need of the animal, as one traces the phylogeny existing in vertebrates. Tumarkin (1948) has described the vestibulo-ossicular and vestibulo-quadrate mechanisms from primitive vertebrates. It is interesting to observe how the vestigeal organs have cleverly adapted to serve the perception of the low energy acoustic vibrations in the rarified surrounding in higher animals. It appears that the mammalian stapes is derived from columella auris, incus from quadrates and malleus from articular bone of ancestral vertebrates. Furthermore their phylogenetical analogues may mimic the developmental anomalies, congenital malformations and geneticdisordersoccasionallyobserved amongst the cases of microtia and congenital deafness. Being articular in origin, morphologically the malleus originated from lower jaw and incus is derived from quadrate, and similarly belongs to upper jaw of the primitive vertebrates. The human ossicles appear to have no connection with vestibular apparatus unlike the Weberian ossicles and also have no contribution from the vertebral spines unlike those in primitive fishes.