Otic notch

Skull of Sclerocephalus, showing the otic notches
A dark brown, textured, approximately triangular, fossilized skull with two large orbits in the centre. At the back of the skull behind each orbit is an indent, which are both circled and have arrows pointing into the indents in cyan.
Skull of Sclerocephalus (photo credit: Ghedoghedo) with otic notches indicated.

Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Otic notches are one of the features lost in the evolution of amniotes from their tetrapod 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.[1] The otic notch instead functioned as a spiracle, at least in the early forms.[2]

References[edit]

  1. ^ 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
  2. ^ Laurin, M. (1996): Hearing in Stegocephalians, from the Tree of Life Web Project
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