One of the most primitive snake fossils have debunked the belief that the slithery reptiles had originated in the sea, suggesting instead that they were the creatures of land.

The animal, which lived at the same time as the dinosaurs, probably emerged from a line of burrowing reptiles that eventually lost their legs.

Where and how snakes diverged from their legged cousins the lizards is still a mystery.

The debate over snake origins has been hampered by the scarcity of transitional fossils.

But new fossils from eastern Wyoming, US, belonging to the ancient snake Coniophis precedens – which lived some 65-70 million years ago – could help clear up the mystery.

According to the analysis by Nicholas Longrich from Yale University and his colleagues, Coniophis lived in a floodplain environment and “lacks adaptations for aquatic locomotion”.

They describe it as a “transitional snake, combining a snake-like body and a lizard-like head”.

“This thing quite probably would have had small legs,” the BBC quoted Dr Longrich as saying.

The ancient reptile’s small size, along with physical features of its spine, suggests that it burrowed. And analysis of its jaws revealed that it fed on relatively large, soft-bodied prey.

But they did not have the flexible jaws that allow modern-day snakes to swallow prey many times their own body size.

“The genesis of the Serpentes (the biological name that defines what we understand as snakes) that began with the evolution of a novel means of locomotion, followed by adaptations facilitating the ingestion of ever larger prey, thereby enabling snakes to exploit a wider range of ecological niches,” the researchers wrote.

The study appears in the journal Nature.