Otic notch
Otic notches are invagination in the posterior margin of the skull roof, one behind each orbit. Such notches are found in labyrinthodonts and some of their immediate ancestors, but not their reptilian descendants. The presence or absence of the otic notches is one of the traits used to separate the amniotes from the amphibian grade tetrapods.
The notches have been interpreted as part auditory structure, and is often shown holding a tympanum similar to those seen in modern anurans. Analysis of the columella (the stapes in amphibians and reptiles) of labyrinthodonts indicate it did not function in transmitting low energy vibrations, thus rendering them effectively death to air-born sound.[1] The otic notch did in stead function as a spiracle, at least in the early forms.[2]
References
- ^ Lombard, R. E. & Bolt, J. R. (1979): Evolution of the tetrapod ear: an analysis and reinterpretation. Biological Journal of the Linnean Society No 11: pp 19–76 Abstract
- ^ Laurin, M. (1996): Hearing in Stegocephalians, from the Tree of Life Web Project