After thousands of years trapped beneath the ice, their young faces are still covered in fur. You can even make out the whiskers on their cheeks and the tips of their sharp retractable claws.

Named for the Siberian riverbank where they were found, Uyan and Dina are the most complete cave lion remains ever discovered. They could prove key to learning more about a species that became extinct over 12,000 years ago.

Over the summer of 2015, flooding along the Uyandina River exposed the ice lens where the cubs were buried. By a stroke of luck, a team of contractors was in the area collecting mammoth tusks. One worker, Yakov Androsov, spotted the remains through a crack in the ice.

Knowing they had uncovered the remains of a feline predator, Androsov immediately placed the cubs in a glacier to prevent thawing.

The cave lion once roamed everywhere from the British Isles to the Yukon in Canada

After so many years trapped in the harsh Siberian cold, the cubs are in surprisingly good condition.

"Their woolen cover, legs, tails, ears, eyes, and even moustaches were preserved," says Androsov.

While they cannot say for certain how old the remains are, Androsov says previous findings suggest they are more than 12,000 years old.

"The most likely cause of their death is a collapse of soil, which walled up the lion's den," says Androsov.

The cubs were probably between two and three weeks old when they died, as their baby teeth had not yet come through, according to Albert Protopopov, head of the Department of Mammoth Fauna Study at the Academy of Sciences of the Republic of Sakha (Yakutia). They were the size of well-fed housecats, and he says it is unclear if they had opened their eyes for the first time.

Until now, everything we knew about cave lions came from Stone Age art and fossilised bones.

One of the largest feline predators of the ice ages, the cave lion made its way from Africa to Europe about 700,000 years ago, gradually spreading to most of North Eurasia. The size of a modern-day Siberian tiger, the cave lion once roamed everywhere from the British Isles to the Yukon in Canada.

Plans for a comprehensive study are underway, with scientists around the world eager to contribute. Aside from determining the cubs' exact age, Protopopov hopes the findings will shed light on their lifestyle, family connections and nutrition, as well as the origin of the species.

Valery Plotnikov, chief researcher at the Academy's Department of Mammoth Fauna Study, has planned a summer expedition to further explore the area where the cubs were found.

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