Oldest Ichthyosaur in History Discovered on Remote Arctic Island

Bones discovered on the Arctic Island of Spitsbergen hint that the old marine reptile called ichthyosaur inhabited the oceans longer than was assumed.

The remains date back to 250 million years and are the oldest evidence of ichthyosaurs seen. The species captured by the bones were large and well-adapted to marine life before ichthyosaurs emerged.

It means we need to revisit our timeline of ichthyosaurs. They probably appeared before the End-Permian Mass Extinction that occurred 251.9 million years ago instead of evolving because of the event, as earlier suggested.

“These tetrapods were seagoing pioneers,” wrote a team of paleontologists headed by Benjamin Kear of Uppsala University in Sweden. 

Researchers have discovered the oldest known remains of a giant ancient oceanic reptile, known as an ichthyosaur, on a remote Arctic island, offering new evidence of how the creature may have evolved. https://t.co/Mop9yuMRwp

— CBS Mornings (@CBSMornings) March 15, 2023

Living alongside dinosaurs in the Mesozoic Era, ichthyosaurs were marine reptiles that dominated Earth’s oceans.

What was Ichthyosaur Like?

The earliest ichthyosaur fossils were small (about 1 m long) and slender. As they chased prey, their small vertebrae presented flexibility to change directions and speed up.

Ichthyosaurs strongly resemble present dolphins if dolphins were giant aquatic lizards, not mammals.

They evolved from land dwellers to sea creatures in the Early Triassic, thriving till the Late Cretaceous, when climate change and slow adaptation brought their time to an end about 95 million years ago.

Other factors like food availability, competitors, and migratory routes may have contributed to their extinction.

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Despite their terrestrial origins, they quickly adapted to aquatic life. Their legs became fins, their snouts elongated and had fish-snatching teeth, and their bones turned spongy like modern cetaceans.

Ichthyosaurs, for a while, were amongst the deadliest predators swimming in the oceans. However, a rocky outcrop on Spitsbergen could change this origin story.

Woop our new paper in @CurrentBiology is out! The oldest ichthyosaur in the world is from Svalbard! Paper link here: https://t.co/7TTTX1xsQ1 #OpenAccess of course 🙂

— Aubrey J. Roberts (@SeaMonsters2013) March 13, 2023

In a valley known as Flowerdalen, erosion has washed mountains to uncover rock millions of years ago, with a complete fossilized catalog of creatures that lived there — coelacanths, amphibians, fish, and sharks.

Paleontologists dug out items of interest in 2014 and shipped them to Uppsala University for labeling and analysis.

Amongst them were things we didn’t expect to see in 250 million-year-old fossil beds: 11 tail vertebrae from an adult ichthyosaur.

The bones looked like bones of ichthyosaurs that came later, with a completely spongy marine tetrapod composition.

They also showed the animals were large and well-formed. It was already well adapted to marine life as a reptile within 2 million years of the last days of the End-Permian Mass Extinction.

Just How Old were these Creatures?

Knowing that marine reptiles diverge between 1.7 and 17.7 million years according to beliefs, ichthyosaurs may have been present in the world’s oceans before the historical Earth’s largest extinction event.

The End-Permian Mass Extinction cleared about 81 percent of the Earth’s marine species, and ichthyosaurs were ready to take over.

“We suggest these preludial marine reptiles likely evolved before the End-Permian Mass Extinction,” the researchers wrote, “but underwent ecological differentiation and niche diversification into smaller waters dominated by amphibians versus deeper water dominated by ichthyopterygians in the nascent dispersal of aquatic tetrapods in the earliest Triassic.”

Paleontologists will search Spitsbergen and elsewhere for more evidence of this revised ichthyosaur timeline.