Otic notches are invaginations in the posterior margin of the
skull roof
The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
In comparat ...
, one behind each
orbit. Otic notches are one of the features lost in the evolution of
amniote
Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are distin ...
s from their
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsid ...
ancestors.
The notches have been interpreted as part of an auditory structure and are often reconstructed as holding a
tympanum similar to those seen in modern
anurans. Analysis of the ''columella'' (the
stapes in amphibians and reptiles) of labyrinthodonts however indicates that it did not function in transmitting low-energy vibrations, thus rendering these animals effectively deaf to airborne sound. The otic notch instead functioned as a
spiracle, at least in the early forms.
[Laurin, M. (1996)]
Hearing in Stegocephalians
from the Tree of Life Web Project
The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth.
This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site h ...
References
{{Reflist
Skull
Vertebrate anatomy
Human head and neck