Mysterious Bone: The monster has spread with amazing speed around the world

(This issue It was first published in Forskning.no).

– This is the reptile's answer to the sea lion, says Jørn Hurum, professor of paleontology at the University of Oslo.

– Imagine a cross between a sea lion and an otter with a slightly long neck. It has webbed arms and legs and a mouth with lots of sharp teeth for catching fish and squid.

This is how Hurum describes the deceased owner of the bone, which he and his colleagues are now presenting in the scientific journal Current Biology.

However, it is not the animal itself that makes this discovery special. The fossil's origins date back to Nothosaurus, a well-known marine reptile from the Triassic period.

But the age and location where the fossil was found make it quite unique:

This is the oldest fossil of a marine reptile ever found in the Southern Hemisphere, says Hurum.

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It is of great importance to our knowledge of the developments that occurred on Earth after the greatest disaster known to life.

Huge disaster

252 million years ago, Earth turned into hell.

The largest known volcanic eruption in the planet's history filled the atmosphere with greenhouse gases, and the global temperature rose by 10 to 15 degrees. Seawater in some parts of the Earth maintained temperatures as high as 40 degrees, and about 90 percent of all species found in the sea became extinct.

Life simply took a bite out of her and she stopped counting.

But it didn't last long.

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Because towards the poles in the north and south the conditions were more suitable for living. And here began a new success story in the development of life:

Reptiles that live in the sea.

Move from land to water

The starting point was the reptiles that lived on land.

At the same time that many large sharks and bony fish died, some of these land-dwelling reptiles gravitated toward the water.

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Within a relatively short time – a few million years – many reptiles have adapted to life in water. The body became streamlined and the legs and arms turned into gloves or flippers.

These water-adapted reptiles have become the new predators of the sea. Finds from Svalbard, North America, and China show that it spread rapidly across the Northern Hemisphere.

But what about the south?

Until now, we have had no traces of sea-dwelling reptiles in the Southern Hemisphere from the first tens of millions of years after the Great Cataclysm. Did these animals get there much later?

This is where the new fossil comes in.

Mysterious fossil

In fact, the fossil was found a long time ago, says Benjamin Kerr of Uppsala University. He has worked with Hurum for a number of years and has made several discoveries in Svalbard. But Kerr is originally from Australia.

At the end of 2018, my colleague, Euan Fordyce of the University of Otago in New Zealand, told me about a mysterious marine reptile fossil from the South Island that geologists had found in 1978, Kerr wrote for forskning.no.

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The fossil consists of a single, well-preserved vertebra from a sea-dwelling reptile. But the discovery was made in loose clumps in the river. Researchers had an idea about the geological layer and the time it came from, but this was never confirmed.

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Thus the bone was forgotten in New Zealand's national fossil collections.

“Unfortunately, Ewan passed away before I could visit him to see the specimen, but last year we were finally able to organize the loan of the fossil during our research and fieldwork visit in Australia,” Kerr wrote.

The bone was properly cleaned and examined at the Norwegian Center for Paleontology at the University of Oslo's Natural History Museum. That's when it became clear how special he was.

Notosaurus is 246 million years old

Remains of sediments and fossil shells on the bones revealed that the age of the vertebra was a whopping 246 million years, that is, only six million years younger than the great catastrophe.

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Aubrey Roberts, a researcher at the University of Oslo and the Natural History Museum in London, says there was no doubt that the bone came from Notosaurus.

-We have found more complete skeletons of notosaurs in many places in the Northern Hemisphere. This enables us to identify individual bones, she says.

A single bone can reveal which species of nothosaur it belonged to.

Vertebrae vary a lot from one species to another, so it's very easy to compare them and figure out which group they belong to, says Roberts.

Thus, the New Zealand greatness belongs to a well-known type of reptile that lives in the sea, but it lived 40 million years before other similar reptiles were discovered in the Southern Hemisphere.

It spread early

“We were surprised that it was so old,” says Hurum.

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-This must mean that nothosaurs were able to disperse very far and very early.

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Previous discoveries of notosaurs in the Northern Hemisphere suggest that the animal evolved here. They then spread southward along the coasts of Pangea – the huge continent that at that time included all the landmasses on the globe.

Hence this movement from north to south must occur quickly.

But for now, scientists don't know how the animals got so south, across dangerously hot seas at the equator. It is not even known which side of the supercontinent they traveled along.

However, Hurom has great hope of finding better answers in the future.

– Just scratch the surface

The professor expects to find new fossils in the Southern Hemisphere that tell more about the migration of marine reptiles.

Perhaps the reason we only get finds from the north is simply because that's where we looked for fossils.

“We've only scratched the surface,” says Hurum.

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– Only in recent years have people begun to search in South America, Africa and other regions in the south. We know that there is much more to be found and that the results will change our knowledge.

Our story of the evolution of life will change. New fossils will emerge that will force us to think again, Horum predicts. He thinks it's fun.

Paleontology is actually one of the few fields where you can change textbooks with a hammer and chisel, he says.

reference:

B. P. Kear, A. J. Roberts, G. Young, M. Terezow, D. J. Mantle, I. S. Barros & J. H. Hurum, Oldest southern sauropterygians reveal globalization of early marine reptiles, Current Biology, June 2024. summary.