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The ear region of the Proboscidea (Afrotheria, Mammalia) : anatomy, function, evolution

Abstract : Elephants are among the few mammals able to hear infra-sounds, and they display a unique locomotor behavior. It corresponds to specializations of their sensory organs contained in the inner ear: the cochlea (audition) and the vestibular system (spatial orientation). While only three species are living today, they were a much more diverse group found in five continents and with a 60 Ma-long history. We provide here the first comprehensive morphological and functional study of the ear region (petrosal, bony and membranous labyrinths) of extant elephants using 3D CT scan techniques. Additionally, we describe and compare the petrosals of fourteen extinct proboscidean genera in order to shed light on the evolution of this anatomical complex in the Proboscidea. The results show that some features of the petrosal and bony labyrinth of extant elephants - such as the number of turns of the cochlea – display a noticeable level of intra-specific variability. Our analysis includes the earliest-known proboscideans and suggests that the petrosal and bony labyrinth morphology evolved gradually during the first half of the proboscidean evolutionary history, but also that the modern morphotype exhibited in elephants was probably already acquired in deinotheriids and generalized in elephantimorphs. Functional inferences on the locomotor behavior and the audition of extinct proboscideans confirm these observations. This work hence provides new insights on the evolution of a major anatomical region hitherto poorly known in an emblematic group of mammals.
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  • HAL Id : tel-01888332, version 1

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Arnaud Schmitt. The ear region of the Proboscidea (Afrotheria, Mammalia) : anatomy, function, evolution. Vertebrate Zoology. Museum national d'histoire naturelle - MNHN PARIS, 2016. English. ⟨NNT : 2016MNHN0011⟩. ⟨tel-01888332⟩

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