Fossil Record 21(1): 33-45, doi: 10.5194/fr-21-33-2018
Relationships of cochlear coiling shape and hearing frequencies in cetaceans, and the occurrence of infrasonic hearing in Miocene Mysticeti
expand article infoIndira S. Ritsche, Julia M. Fahlke, Frank Wieder§, André Hilger|, Ingo Manke|, Oliver Hampe
‡ Museum für Naturkunde – Leibniz-Institut für Evolutions- und Biodiversitätsforschung, 10115 Berlin, Germany§ Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 44–46, 12203 Berlin, Germany| Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
Open Access
Abstract

Baleenwhales (Mysticeti) are known to use low frequencies (LF; 200 Hz and below)and infrasound (< 20 Hz) for communication. The lowest hearinglimits of toothed whales (Odontoceti), which are able to produce ultrasound(> 20 kHz), reach low frequencies. Researchers have tried tounderstand the evolution of LF and infrasonic hearing in mysticetes bylinking the shape of the inner ear cochlea or individual cochlearmeasurements to known hearing frequencies and making inferences to extinctspecies. Using landmark-based shape analysis of complete cochlear coiling, weshow that cochlear coiling shape correlates with LF and high-frequency (HF;> 10 kHz) hearing limits in cetaceans. Very LF ( 50 Hz)and infrasonic hearing are associated with, for example, a protruding second turn, adescending apex, and a high number of turns. Correlations between cochlearand cranial variables and cochlear and cranial shape indicate that low LFhearing limits are furthermore connected to longer cochleae and relativelylarger cranial widths. Very LF hearing in Mysticeti appeared in the middleMiocene, and mysticete infrasonic hearing had evolved by the late Miocene.Complete cochlear coiling is suitable for estimating hearing limits incetaceans, closely approximated by cochlear length times number of cochlearturns.