Some of the best hearing in the animal kingdom belongs to mammals, including humans and bats, thanks to the snail-shaped coiling of the cochlea, a key part of the inner ear. A 150-million-year-old fossil of a mammal, Dryolestes leiriensis, has revealed how this key innovation evolved.
The fossil has a bony inner ear structure (pictured) containing auditory nerves, similar to that of its contemporary relatives. But this structure is curved rather than coiled. Zhe-Xi Luo at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, and his colleagues suggest that the cochlea was innervated before it evolved into today's curved shape.
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Evolution: Ear roots. Nature 466, 668 (2010). https://doi.org/10.1038/466668d
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DOI: https://doi.org/10.1038/466668d