The oldest fossils of an important marine reptile were discovered in the Arctic

A computed tomography image and a cross section show the internal bone structure of the vertebrae of the oldest known Ichthyosaur (REUTERS) (OYVIND HAMMER AND JORN HURUM /)

The ichthyosaurs They were a successful group of marine reptiles that thrived during the age of dinosaurs, some of which reached up to a few 21 meters in lengthsurpassed in size in the history of the Earth’s oceans only by the largest whales.

However, its origins have been somewhat of a mystery. Some fossils from about 250 million years ago unearthed in a remote and hostile place – the Norwegian island of Spitsbergen, in the Arctic – now provide surprising data about its appearance.

The researchers claim to have found remains of the oldest known ichthyosaur, which lived about 2 million years after the worst mass extinction on Earth, which ended the Permian and killed about 90% of the species in the midst of a huge Siberian volcanism. The 11 discovered tail vertebrae indicate that the animal was about three meters long, making it a a big predator.

Like the mammalian whales and other reptilian lineages that have inhabited Earth’s oceans, ichthyosaurs evolved from ancestors that walked the land and They went through a transition from land to sea.

The researchers thought that any ichthyosaur living 250 million years ago would be a primitive form, not far removed from its terrestrial ancestors. Fossils showed that this one, which has not yet been given a scientific name, was quite advanced anatomically.

An artist’s reconstruction shows the oldest known ichthyosaur (Esther van Hulsen/REUTERS)

“The real surprise was that, after a series of geochemical, computerized microtomographic and microstructural analysis of the bones, the vertebrae turned out to be from a very advanced, fast-growing ichthyosaur, probably warm-blooded, very large (about 3 meters) and totally oceanic,” said Benjamin Kear, from the Museum of Evolution at Uppsala University (Sweden) and lead author of the research published in the journal Current Biology.

“The implications of this discovery are manifold, but most importantly it indicates that the long-anticipated transitional ancestor of the ichthyosaur must have appeared much earlier than suspected”, he added.

many ichthyosaurs they looked like dolphins, but with vertical instead of horizontal tail fins. Others looked like big whales. Among the largest was the Shastasaurus, about 21 meters. They ate fish and squid. Fossils show that they gave birth to their young.

(By Will Dunham – Reuters)

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