Scientists have unravelled the mystery of a fossil left in the Arctic almost 80 years ago
In 1948, British researchers discovered the remains of an unusually large ancient animal on the summit of an Arctic island. They were unable to remove the entire skeleton: they took photographs, collected some of the bones, and left the rest out in the open. Decades later, the find was rediscovered, and palaeontologists have now established that they were dealing with a species previously unknown to science — and the largest known representative of its unusual group.
The discovery was made on Bjørnøya, or Bear Island, which forms part of the Svalbard archipelago.
The scientists on the first expedition realised they were looking at a large fossilised skeleton, but were unable to fully excavate and transport it in the harsh Arctic conditions. They took only some of the bones and photographed the remaining fragments.
Over time, the researchers had all but given up hope that the fossil had survived the freezing temperatures, wind and precipitation.
But in 1984 — 36 years after the initial discovery — a Norwegian expedition unexpectedly rediscovered it.
Its condition had deteriorated significantly: some of the bones had disappeared, whilst others had cracked and crumbled. After a week of excavations, the remaining fragments were finally recovered.
Details
The most interesting part came many years later, when experts had finally prepared the material for analysis.
Palaeontologists realised that they were dealing with a member of the plagiosaurids — unusual aquatic dark-spondyls from the Triassic period. These animals were characterised by extremely broad and flat heads and lived in bodies of water where they could lie in wait for prey.
However, the Arctic specimen turned out to be quite extraordinary even amongst them.
Part of the skull had been destroyed during the decades it had spent exposed to the elements. To reconstruct it, the researchers turned to photographs taken as far back as 1948.
It was these old photographs that made it possible to reconstruct the elements that no longer exist today.
The reconstruction revealed impressive dimensions.
The animal’s skull was approximately 70 centimetres wide, but only about 21 centimetres long. Viewed from above, it resembled a huge semicircle or a boomerang.
The animal itself, according to the researchers’ estimates, grew to approximately 2.7 metres in length.
In terms of size, it significantly outstripped other known plagiosaurids. Scientists have classified the find as a new species and named it Arctobatrachus urdensis.
Its large mouth and teeth suggest that it was a large predator. However, it is still too early to call it the undisputed ‘apex predator’ of the ecosystem: anatomy alone is not enough to fully reconstruct the food chain.
Plagiosaurids were very unusual animals.
Their bodies became increasingly flattened, whilst their heads were exceptionally broad. Some members of the group probably spent most of their time near the bottom of water bodies, opening their mouths wide to suck in any prey that happened to be nearby.
But Arctobatrachus urdensis is interesting for more than just its size.
Analysis of its position on the evolutionary tree has shown that it was an early member of the plagiosaurids. This provides a better understanding of how their characteristic flattened body shape gradually evolved.
Researchers suggest that early forms were more agile swimmers, whilst later members of the group adopted a more sedentary lifestyle.
Despite its outward resemblance and popular description as an ‘amphibia-like animal’, Arctobatrachus should not be imagined as a giant modern salamander or frog.
It belonged to the temnospondyls — a long-extinct group of ancient tetrapods that was widespread during the Palaeozoic and Mesozoic eras.
The new species lived in the Triassic world, more than 200 million years ago, when the Earth’s ecosystems were still reorganising following the largest mass extinction in the planet’s history.
Why this is important
The story of Arctobatrachus urdensis is unusual even by palaeontological standards.
A key part of the fossil lay exposed in the Arctic for decades and was partially destroyed before scientists were able to study it properly.
However, photographs taken almost 80 years ago have preserved information that was lost in the fossil material itself.
As a result, the find – which could not physically be recovered in its entirety in 1948 – has, decades later, been identified as a new species and the largest known plagiosaurid.
Source
Study: Rainer R. Schoch, Sanjukta Chakravorti, Florian Witzmann, Franz-Josef Lindemann. A giant plagiosaurid temnospondyl from Bjørnøya (Svalbard, Norway) and the origin of the plagiosaurid body plan.
Journal: Papers in Palaeontology, 2026.