Ichthyosaurs Had Surprisingly Dense Ribs, New Study Finds

Long before whales ruled the oceans, dolphin-shaped marine reptiles called ichthyosaurs patrolled the same waters. New research from the Natural History Museum at the University of Oslo suggests their rib cages may have done a job modern whale ribs don’t: acting as ballast to help them dive. The findings appear in the journal PeerJ .

Cryopterygius kristiansenae , a species of ophthalmosaurid ichthyosaur from the Jurassic of Svalbard. Image credit: Esther van Hulsen.

“Ichthyosaurs were secondarily aquatic reptiles that dominated the world’s oceans through much of the Mesozoic Era, with a fossil record spanning from the Early Triassic (250 million years ago) to their final demise in the early Late Cretaceous (93 million years ago),” said senior author Dr. Lene Liebe Delsett and and colleagues.

“They are among the few aquatic amniotes to acquire a fully aquatic lifestyle in the open ocean, matched only by that of modern cetaceans.”