First eurhinodelphinid dolphin from the Paratethys reveals a new family of specialised echolocators

ABSTRACT

Eurhinodelphinids are a family of extremely long-snouted dolphins that once was widespread across the North Atlantic realm, but so far has not been recorded from the epicontinental Paratethys Sea. Here, we describe a new specimen of Xiphiacetus cristatus, including the cranium, left ear bones and a partial mandible, from the Middle Miocene (Badenian) of Austria. Our new fossil is the first record of this species outside the North Atlantic proper, and the first unequivocal record of eurhinodelphinids from the Paratethys. Its presence suggests a local invasion via the Mediterranean, and corroborates the persistence of an active marine gateway between the Mediterranean and the Central Paratethys throughout the Middle Miocene. Measurements of the bony labyrinth reveal that X. cristatus likely employed narrow-band high-frequency echolocation, making eurhinodelphinids only the second extinct odontocete family with this trait. Marked non-orthogonality of the semicircular canals suggests that X. cristatus was unsuited to rapid head movements, and thus more likely a benthic forager than a snap feeder.

KEYWORDS:

• Odontoceti
• cochlea
• 90var
• head movements
• hearing
• echolocation

Acknowledgments

We thank Zementwerk Lafarge Retznei and Johannes Zweytick for help with the excavation, Björn Berning and Mathias Harzhauser for facilitating the study of the specimen, Rachel Racicot for advice on cochlear measurements, and two reviewers for their constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2022.2077645

Additional information

Funding

This work was partly funded by a Marie Sklodowska-Curie Global Postdoctoral Fellowship [656010/MYSTICETI] to FGM.