This species was primitive, retaining the features of amphibians who lived about 30 million years earlier, say the experts.

Or were these ancient turtles somehow adapted to the extreme cold and long winter darkness?

The find by scientists from St Petersburg University is the most northerly discovery of non-sea turtles.

The turtles date from about 130 million years ago.

The turtles were living in Yakutia, which is now Russia's - indeed the world's - coldest inhabited region.

Skull bone of the turtle found at Teete. 3D reconstruction of the turtle's skull. Pavel Skuchas

This species was primitive, retaining the features of amphibians who lived about 30 million years earlier, say the experts.

They were found near Vilyuy River at the Teete site, home to dinosaurs in the same period when the turtles lived here, a unique site in the polar regions of northern hemisphere.

Biologist Dr Pavel Skuchas said: ‘The fact of the presence of turtles is very interesting.

'It shows that there was no cold at that time in this area, despite the fact that these are polar regions.

‘These are the most northern finds of non-sea turtles.’

Archaic turtle, Heckerochelys romani gen. et sp. nov. from the Middle Jurassic of Moscow region, which is similar to the Arctic turtle. Picture: Vladimir Sukhanov

He is especially interested how turtles coped with the long winter darkness and summer white nights.

‘We are trying to find out what adaptations these animals - turtles, salamanders, dinosaurs and others - had to polar conditions,’ he said.

In fact, the Suntarsky district of Yakutia, where the finds were made, is not now in the Arctic, but Dr Skuchas says that in the era of the little and large turtles and dinosaurs it definitely was.

The turtle's bones were found near Vilyuy River at the Teete site, home to dinosaurs in the same period when the turtles lived here.

Yakutian geologist and palaeontologist Dr Pavel Kolosov said the Teete site is unique.

'There are hundreds of known locations with the remains of dinosaurs and other groups of vertebrates around the world.

‘But only a few of them lie in the region of the polar latitudes of the Mesozoic era.

‘Among them, only four locations belong to Late Jurassic-Early Cretaceous.

Excavations at Teete site in 2017 and general view of Teete site in 2002. Pictures: Pavel Skuchas, YSIA

‘Three are in the southern hemisphere and only one in the northern.

‘This one is Teete.’

The interesting finds at this site were made by scientists seeking for mineral deposits.

The turtle find, for example, was made by scientists from St Petersburg State University, the Institute of Geology of Diamond and Noble Metals of the Siberian Branch of the Russian Academy of Sciences, and the University of Bonn (Germany).