Until now, scientists have not known at what stage turtles adapted to water.
But excavations on the Isle of Skye have yielded the remains of at least six primitive turtles which represent the 'missing link' in the evolution of turtles that palaeontologists have long sought.
The discovery of Eileanchelys waldmani, a previously unknown species, have given scientists proof of the first stage at which turtles started swimming.
Jérémy Anquetin, of the Natural History Museum and one of the researchers who analysed the fossilised turtles, said: "Although the majority of modern turtles are aquatic forms, it has been convincingly demonstrated that the most primitive turtles from the Triassic, about 210m years ago, were exclusively terrestrial.
"Until the discovery of Eileanchelys, we thought that adaptation to an aquatic habitat might have appeared among primitive turtles but we had no fossil evidence of that.
"Now we know for sure that there were aquatic turtles around 164m years ago. This discovery also demonstrates that turtles were more ecologically diverse early in their history than had been suspected before."
The turtle fossils were recovered from a slab of rock cut out in 2004. Each was encased in the slab and it took months to release them.
They were analysed by researchers from the Natural History Museum and University College London.
They concluded that the newly discovered species was aquatic because the fossils were found in rock that once formed the bottom of a lake or lagoon, and because unlike the remains of contemporary land animals, which were fragmented having been washed into a pool, the turtles were relatively complete and articulated.
The fossils are now in the collection of National Museums Scotland.Original here