Evidence of the earliest aquatic turtles has been discovered in Scotland, scientists at the Natural History Museum report today.
The fossils are from the Middle Jurassic period and are about 164 million years old and could be a missing link between land-based and aquatic turtles. They were uncovered from rocks on the Isle of Skye off the north-western coast of Scotland by a team including researchers at University College London (UCL).
The oldest turtle fossils date from about 210 million years ago in the Late Triassic period and came from land-living rather than aquatic animals.
'This new find provides us with the best-ever view of turtle evolution during the Middle Jurassic,' says Paul Barrett, fossil expert at the Natural History Museum. 'It fills an extensive gap in the history of the group that has long frustrated palaeontologists.'
This new turtle species, called Eileanchelys waldmani, was relatively small, with a shell around 20cm in length. It lived in lagoons and lakes alongside salamanders and sharks, in a habitat that was very different from today’s Isle of Skye.
'Until the discovery of Eileanchelys, we thought that adaptation to aquatic habitats might have appeared among primitive turtles but we had no fossil evidence of that,' says Jeremy Anquetin, a French PhD student at the Museum and University College London who led the research.
'Now, we know for sure that there were aquatic turtles around 164 million years ago.'
The team of scientists spent months carefully chipping and dissolving away the rock to reveal 4 well-preserved turtle fossils as well as remains of at least 2 others. These are the most complete turtle specimens from the time of the Middle Jurassic.
'It was originally thought that we had the remains of only one turtle in the block of rock we collected,' says Barrett. 'However, during the laborious task of removing the skeletons from the rock, it became clear that we were dealing with not one, but a group of turtles'.
Most modern turtles are aquatic and live in tropical areas of the world. There are about 300 species alive today and many of these are endangered.
Turtles are one of the oldest reptile groups and belong to the Order Testudines that includes tortoises and terrapins. They are more ancient than lizards and snakes.
The largest marine turtle is the leatherback that may reach 1.8m (6ft) in length. Like other aquatic turtles, they leave the water to dig burrows and lay their eggs in the sand. The leatherback is listed as Critically Endangered by the IUCN Red List.
Barrett concludes, 'We hope to go back and continue the work on Skye - who knows what other surprises may be waiting for us when we return?'
This work was funded by the National Geographic Society. The research is published in the journal Proceedings of the Royal Society B: Biological Sciences. The Eileanchelys waldmani specimens are at the National Museums Scotland.