Gigantic collection of fossils concealed an ancient surprise

“We aren’t sure how the bonebed was formed,” says Aubrey Jane Roberts, a palaeontologist at Norway’s Natural History Museum.

She does, however, know very well how it was discovered.

During an expedition to the Marmier Mountain on Svalbard in 2015, the researchers walk in a line up the mountainside. They are searching for fossils.

Suddenly, someone shouts.

It's Stig Larsen. He is volunteering for the fieldwork because he's incredibly good at spotting fossils in the grey rock pile.

Now Larsen has found a whole heap of them.

An approximately five-centimetre thick layer in the mountainside consists almost exclusively of bones. As the researchers dig, vertebrae and shark teeth and pieces of ribs emerge in droves.

Some process or other has gathered the fossils into a layer that extends across and into the mountainside. Not as whole skeletons, but jumbled and mixed together. Like loose jewels in a pirate's treasure.

In the years that follow, the researchers continue to excavate many square metres of this layer.

They take everything home to Oslo in plastic bags.

And now, after thousands of hours of examination, they present the bones and the enormous significance they believe they may have, in Science.

The discovery graces the cover of a recent issue of the highly regarded scientific journal.

“For researchers, this is like getting on the cover of Rolling Stone Magazine for a rock band,” says Professor Jørn Hurum, who has also worked on the discovery for several years.

Reveals life just after the catastrophe

Several features make this discovery very special, according to Roberts.

The most obvious thing is the amount and density of fossils.

Just in this small piece there are several fossilised faeces, a vertebra, and many bone fragments and fish teeth, like the one Roberts points to with her fingernail.

The researchers have to crush the rocks to remove the fossils. Here are some of the rocks that are still intact.

So far, the researchers have registered more than 30,000 pieces of bones, teeth, and faeces.

“It’s really unusual to find accumulations of marine fossils like these,” says Roberts.

Age is another special feature of the bonebed.

“The layer was formed 249 million years ago,” says Roberts. “This is just three million years after the largest mass extinction event in Earth's history.”

Some 252 million years ago, huge volcanic eruptions led to such drastic climate changes that the ocean measured over 40 degrees Celsius at the equator. Up to 90 per cent of all life in the oceans died out.

At that time, Svalbard lay at the bottom of a huge marine bay. This means that the bonebed gives us a picture of how marine life recovered shortly after the catastrophe.

And this is where the surprise comes in.

Top predators and a mystery reptile

The third feature of the bonebed is the incredible amount and variety of species found there.

Roberts and her colleagues have found a wide variety of fish and lobe-finned fish.

And a whole bunch of sharks. Some of them are really huge.

Sharks have skeletons made of cartilage, which breaks down easily. Often, all that remains are teeth. But here researchers found this piece of fossilised cartilage.

And there are also remains of armoured amphibians and reptiles.

And perhaps as many as five different species of ichthyosaurs, in completely different sizes.

Some are large apex predators. This is the vertebra of a huge ichthyosaur at least five metres long.

The owner of the vertebrae in this box – Omphalosaurus – was a relative of ichthyosaurs in the medium-sized class.

But some of the reptiles are also small, perhaps only a metre long.

This bone fragment comes from the small, primitive ichthyosaur Grippia.

The bonebed on Svalbard is full of such remains, and has therefore been named the Grippia bonebed.

The researchers have also found bones of a mysterious, crocodile-like reptile that no one has yet been able to identify.

“It’s a mystery reptile, an undescribed species that we’ve found lots of vertebrae of,” says Roberts.

The long vertebra from the unknown reptile is very different from the flat vertebra of an Omphalosaurus.

Thousands of fossilised faeces have turned up too. Inside the faeces are remains of bones, fish scales, squid, and sponges. You can read more about the so-called coprolites here.

Astonishingly early ecosystem

Taken together, the fossils form a picture of an astonishingly rich ecosystem, with several different levels of animals eating each other, according to the researchers.

“The bonebed shows that a complex ecosystem of vertebrates emerged very quickly after the extinction,” says Roberts.

“This is the world's oldest ecosystem in which marine reptiles are the top predators,” says Hurum. “The oldest ocean where reptiles ruled is therefore much older than the dinosaurs – and we found it on Svalbard.”

This early ecosystem is surprising.

Previously, researchers assumed that it took many millions of years for life to recover from the catastrophe. That such a diverse network of vertebrates appears to have developed in just a few million years is therefore remarkable.

This, in turn, may provide new knowledge about how evolution works and how life is able to cope with major disasters.

“It's important for understanding what could happen in our future as well,” says Roberts.

Strange and unknown animals

The researchers at the Natural History Museum have spent several years sorting and identifying the fossils by species.

"The process has been incredibly difficult and time-consuming," says Roberts.

Some pieces are so small that it's difficult to determine which animals they belonged to.

And there's probably still a whole career's worth of work to do.

These ancient animals have many features that we still don't know much about.

Like these strange reptiles with round, molar-like crushing teeth.

They were probably used to crush the shells of prey such as ammonites – a type of extinct squid.

There are also ichthyosaur jaws with teeth jutting out in multiple directions.

This is a piece of the jaw of a Grippia ichthyosaur.

The jaw is one of the fossils that was recently presented in the scientific journal Science.

And then there are the unknown species.

In addition to the boxes of bones from the mystery reptile, Roberts has an entire drawer full of fossils that they are still clueless about.

New species might be hiding here.

And the researchers have not even begun to look at fossils that are less than two millimetres in size.

“We’ve barely scratched the surface,” says Roberts.

Many important answers could be hidden in the drawers with 249-million-year-old forgotten body parts.

One question is whether all of these animals evolved over a brief period after the catastrophe.

Or whether some of them might have been survivors from the time before.

A previous discovery may indicate that ichthyosaurs actually originated before the inferno 252 million years ago.

The areas around Svalbard were already located quite far north at this time. Perhaps it was easier to survive there.

A lot of questions

Roberts expects that many questions will be asked when they present their findings to palaeontologists around the world.

A well-known research team in China has made discoveries from the same time period. They found a different story in their data – namely that it took much longer for the ecosystems to rebuild after the catastrophe.

“They will no doubt pounce on our dating,” says Roberts.

“We’ve done everything we can to confirm that the bonebed was built up over a short period of time,” says Roberts.

In other words, that it was formed over a period of a few hundred thousand years, not over millions.

This is extremely important. Because if the layer was formed over a very long time period, it's not certain that the species lived at the same time. Then the fossils would also not provide any picture of which species lived together in ecosystems so soon after the catastrophe.

Several methods show the same answer

The researchers at the Natural History Museum nevertheless believe that a lot of evidence points to the fossils originating from the same place in a fairly short period of time. The bones, for example, show little wear from transport. And several different dating methods give the same answer regarding their age.

Roberts says that she and her colleagues plan to publish more scientific articles on the details of the dating.

She welcomes critical questions in any case.

“That's what makes us better,” she says.

———

Photos:

The two images from Svalbard: Natural History Museum

Other images: Ingrid Spilde

Translated by Ingrid P. Nuse

Read the Norwegian version of this article on forskning.no

Reference:

Roberts et al. 'Earliest oceanic tetrapod ecosystem reveals rapid complexification of Triassic marine communities', Science, vol. 390, 2025. DOI: 10.1126/science.adx7390 (Abstract)

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