Thought to have lived in the late Pleistocene era, a small group of the worms found 40 metres deep in the Siberian permafrost have been thawed out and revived.

The worms are from the long-extinct species Panagarolaimus kolymaensis and were not actually dead, but in a dormant state known as cryptobiosis which renders their vital signs undetectable.

Scientists previously only had evidence nematodes or roundworms were able to remain in this state for up to 40 years, but these creatures coexisted with woolly mammoths.

Professor Teymuras Kurzchalia, senior author of a study of the worms, published in the journal of PLOS Genetics, and emeritus professor at the Max Planck Institute of Molecular Cell Biology and Genetics in Germany, said: "This little worm could now be in line for a Guinness World Record, having remained in a state of suspended animation for far longer than anyone thought was possible.

"That it could be reanimated after 46,000 years left me absolutely flabbergasted.

"It is rather like the fairy tale of Sleeping Beauty, but over a far longer period."

The worms were revived by being given food and water.

They survived for less than a month but have since spawned more than 100 generations of new worms.

To date, scientists know of very few animals capable of suspending themselves in a limbo-like state in response to tough environmental conditions.

Tardigrades, nematodes, and microscopic aquatic organisms, called rotifers, are just a few of the animals known to enter cryptobiosis.

When researchers compared the genomes of Panagarolaimus kolymaensis to one of its living relatives, Caenorhabditis elegans, they found a lot of overlapping genes between the soil worms.

Many of the shared genes are tied to mechanisms involved in surviving harsh environmental conditions.

This is interesting, as Caenorhabditis elegans is usually found in temperate regions, hiding in rotting fruit or plants.

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According to the authors of the study, their findings "indicate that by adapting to survive cryptobiotic state for short time frames in environments like permafrost, some nematode species gained the potential for individual worms to remain in the state for geological timeframes".

Next, the team wants to figure out what role these shared genes play in cryptobiosis, and whether there is an upper limit to how long nematodes can remain in this mysterious state.

"These findings have implications for our understanding of evolutionary processes, as generation times may be stretched from days to millennia, and long term survival of individuals of species can lead to the refoundation of otherwise extinct lineages," the authors of the paper write.