Contact: Jaelyn Eberle
University of Colorado at Boulder
Caption: CU-Boulder associate professor Jaerlyn Eberle, left, and research colleagues collect ancient sharks teeth on Banks Island in the Arctic Circle. Oxygen isotopes in the teeth indicated sharks living in the Eocene Arctic Ocean roughly 50 million years ago were tolerant of brackish water, unlike their shark relatives living today.
Credit: Jaelyn Eberle, University of Colorado
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Related news release: New study: Ancient Arctic sharks tolerated brackish water 50 million years ago