Data from: Evidence for convergent evolution of ultrasonic hearing in toothed whales (Cetacea: Odontoceti)

Toothed whales (Cetacea: Odontoceti) are the most diverse group of modern
cetaceans, originating during the Eocene/Oligocene transition ~38 million
years ago. All extant odontocetes echolocate; a single origin for this
behavior is supported by a unique facial source for ultrasonic
vocalizations and a cochlea adapted for hearing the corresponding echoes.
The craniofacial and inner ear morphology of Oligocene odontocetes support
a rapid (Simocetus and Olympicetus suggest an ability to generate
ultrasonic sound, until now, the bony labyrinths of taxa of this grade
have not been investigated. Here, we use µCT to examine a petrosal of a
taxon with clear similarities to Olympicetus avitus. Measurements of the
bony labyrinth, when added to an extensive dataset of cetartiodactyls,
resulted in this specimen sharing a morphospace with stem whales,
suggesting a transitional inner ear. This discovery implies that either
the lineage leading to this Olympicetus–like taxon lost the ability to
hear ultrasonic sound, or adaptations for ultrasonic hearing evolved
twice, once in xenorophids and again on the stem of the odontocete crown
group. We favor the latter interpretation as it matches a well-documented
convergence of craniofacial morphology between xenorophids and extant
odontocetes.