November 19, 2008

Ancient Turtle Species Discovered On Scottish Island

The Royal Society journals have reported that the earliest turtles known to live in water have been discovered on a Scottish island.

The reptile fossils, thought to be some 164 million years old, were found on a beach in southern Skye, off the UK's west coast.

A team from London's Natural History Museum and University College London (UCL) uncovered them.

Experts say the new species"”embedded in a block of rock at the bay of Cladach a'Ghlinne, on the Strathaird peninsula"”forms a missing link between ancient terrestrial turtles and their modern, aquatic descendants.

The rock contained four well-preserved turtle skeletons, and the remnants of at least two others, forming the most complete Middle Jurassic turtles described to date.

The National Museums Scotland, Edinburgh is now showing the historic specimens.

"Why did turtles enter the water? We have no idea. It's a mystery - like asking why cetaceans went back into the sea," said J©r©my Anquetin, of the department of palaeontology at the Natural History Museum.

"Little by little, we are filling the gaps. Now, we know for sure that there were aquatic turtles around 164 million years ago. Eileanchelys may represent the earliest known aquatic turtle," he added.

"It is part of a new revision we are having about turtle evolution."

The discovery of the new species helps bridge a 65 million-year gap in the story - between the terrestrial "basal" turtles, from the late Triassic, and the aquatic "crown-group" turtles of the late Jurassic.

Anquetin said the former were "heavy-built" land-dwellers, with skulls which were "more reptilian" while the latter were lighter, and closer in appearance to the aquatic, freshwater turtles we know today.

Archaeologists say what happened in between was a mystery, until very recently.

Fossils of three new turtle species, all dating to the Middle Jurassic, have been discovered in Russia, Argentina, and now Scotland in the last two years.

Anquetin said the Scottish fossils are the most complete of them all. "They tell us a lot about how the primitive 'stem turtles' diversified into the varied forms we see today."

He said these "missing links" would resemble a modern freshwater turtle on the outside"”like the ones you can buy in the pet shop.

"The differences are on the inside - in the cranial anatomy. They are small differences but very important. There is no other turtle like this one."

The fossils have now been recognized as a new species, named Eileanchelys to incorporate "Eilean", the Gaelic word for "island".

Anquetin said he liked the idea of giving it a name in Gaelic.

"I chose 'Eilean', so the whole name means 'the turtle from the island'."

But he said the turtles would have lived in a land unrecognizable from the rugged, wind-battered coastlines of modern day Skye.

In the Middle Jurassic, the land mass was much further south, basking in a warm, sub-tropical climate.

According to the authors, the turtles probably lived in a landscape of shallow lagoons and freshwater lakes. Other aquatic species, such as sharks and salamanders, were found alongside the turtle fossils.

Experts say the remains of terrestrial vertebrates, such as lizards and dinosaurs, are "exceptionally rare".

"If [we accept all this evidence], E. waldmani plausibly represents the first aquatic turtles."

Dr. Walter Joyce, an expert in turtle evolution, formerly of the Peabody Museum of Natural History, Yale University, said this new turtle is very exciting.

"Keep in mind that a 65 million year gap used to exist in the fossil record between the oldest known turtles from the Late Triassic and basically modern turtles in the Late Jurassic.

"The new turtle is really quite spectacular in preservation, considering that several complete skeletons are preserved, instead of the usual scrap that has to be pieced together.

"The find confirms that basal turtles were a global phenomenon. It also confirms my research that the split into the primary groups that we see today did not occur until later than originally thought.

"Finally, although it is really difficult to assess the ecological habitat preferences of turtles, the authors make a compelling case that by this stage in evolution turtles had started moving into aquatic habitats."

Joyce was amazed that the team was able to recover such extraordinary material from the icy cold shores of Scotland, an area generally not known for its turtle fossils.


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